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Exposure of teachers and students to noise and airborne hazards in high-school technology-education shops,… Summan, Ahmed Saleh 2016

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   EXPOSURE OF TEACHERS AND STUDENTS TO NOISE AND AIRBORNE HAZARDS IN HIGH-SCHOOL TECHNOLOGY-EDUCATION SHOPS, AND THEIR CONTROL by  AHMED SALEH SUMMAN  B.Sc., King Abdul Aziz University, 2003 M.Sc., King Abdul Aziz University, 2007  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR  THE DEGREE OF  DOCTOR OF PHILOSOPHY  in  THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES  (Occupational and Environmental Hygiene) THE UNIVERSITY OF BRITISH COLUMBIA  (Vancouver)   April 2016  © Ahmed Saleh Summan, 2016  ii Abstract  More than 200 million young employed workers less than 25 years old work in different trades and industries around the world. Around 70% of them work in unhealthy workplaces. In Canada, hundreds of young workers are injured or killed in workplaces every year. In British Columbia, young workers represent the largest population of workers with respect to the rate of work injuries. However, this doesn’t represent the population of students in high-school Technology-Education Shops (TES), who are learning technical skills and exposed to different workplace hazards at the same time. They are not protected by regulations that meet their personal/work characteristics, and the teachers who are responsible for monitoring 30 students in each class are not responsible for occupational hygiene inspection. Consequently, this can put both the student and the teacher at risk from exposure to many workplace hazards in TES, which could adversely affect their health and the quality of education provided. Moreover, an acoustical conflict could exist in these unique, small work environments because they are used as classrooms for learning and as industrial workrooms for fabrication at the same time. Therefore, there was a need to conduct this pilot study to explore and investigate the work and control conditions in 26 TES in British Columbia, included woodworking, metalworking and automotive shops.  This study was carried out by evaluating the acoustical conflict, evaluating the occupational exposures of teachers and students to noise and airborne hazards (wood dust and welding fume), and suggesting suitable control measures to make TES healthy work and learning environments. Final findings indicate that TES provide poor acoustical quality (e.g., high background-noise levels, high reverberation times, and poor speech-intelligibility quality)   iii for learning and working. In addition, TES teachers and students were found to be exposed to unacceptable levels of noise and airborne hazards (wood dust and welding fume). Indeed, these findings indicate that TES are in need of effective acoustical design and hazard-control measures. These suggested control measures include all or some of the feasible and affordable means to improve the quality of TES and make them healthier environments for teachers and students.                                 iv Preface    Ethics Approval Information:  University of British Columbia Behavioral Research Ethics Board  Certificate Number: H11-00361  Student’s Contribution:  The research design, obtaining consent forms and school approvals, research execution, data collection and field measurement, laboratory and statistical analysis were 95% the contribution of the PhD student, with supervision and assistance from the committee.   Scientific Publication: Parts of Chapter 3 “Evaluation of the Acoustical Condition in Technology Educational Shops” and section 4.1 of Chapter 4, have been published in the Journal of Building Acoustics, Volume 22, Number 1 by Ahmed Summan and Murray Hodgson (2015).  Also, parts of Chapter 3, were presented in the International Congress on Acoustics in Montreal by Ahmed Summan and Murray Hodgson (2013).       v  Table of Contents  Abstract ................................................................................................................................ ii Preface ................................................................................................................................. iv Table of Contents .................................................................................................................. v List of Tables ........................................................................................................................ ix List of Figures ........................................................................................................................ x List of Symbols and Abbreviations ........................................................................................xii Acknowledgments ................................................................................................................ xv Dedication .......................................................................................................................... xvii 1 Introduction ................................................................................................................... 1 1.1 Research background .........................................................................................................2 1.2 Technology educational shops ............................................................................................3 1.2.1 Background, definition and objective ..................................................................................... 3 1.2.2 General description of TES design and settings ...................................................................... 5 1.2.3 Health and safety in TES: Responsibilities ............................................................................... 6 1.2.4 Schedule and nature of teaching and working in TES ........................................................... 10 1.2.5 Description of specific types of TES and related tasks .......................................................... 11 1.3 The shape of the problem ................................................................................................ 17 1.3.1 TES teaching and working: Acoustical conflict ...................................................................... 17 1.3.2 TES teachers and students’ exposure to hazards: TES health and work safe practices ........ 18 1.4 Potential exposures of interest ......................................................................................... 21 1.4.1 Noise ...................................................................................................................................... 21 1.4.2 Wood dust ............................................................................................................................. 28 1.4.3 Welding fume ........................................................................................................................ 35 1.5 Existing knowledge .......................................................................................................... 39 1.5.1 Acoustical conditions in classrooms ...................................................................................... 39 1.5.2 Noise in TES and small industrial shops ................................................................................ 43 1.5.3 Wood dust in small industrial woodwork shops and TES ..................................................... 46 1.5.4 Welding fume in small industrial shops and TES ................................................................... 48 1.5.5 Summary ............................................................................................................................... 50 1.6 Motivation for the study .................................................................................................. 51 1.7 Thesis objectives .............................................................................................................. 53 1.8 Overview of the thesis ..................................................................................................... 54 2 Site Selection and Participant Recruitment ................................................................... 58 2.1 Site selection ................................................................................................................... 58    vi 2.1.1 Pre-visits and walkthrough surveys in TES ............................................................................ 58 2.2 Participant selection and recruitment procedures ............................................................. 59 2.2.1 Obtaining permission for participation ................................................................................. 59 2.2.2 Recruitment criteria .............................................................................................................. 60 3 Evaluation of the Acoustical Conditions in TES .............................................................. 63 3.1 Introduction .................................................................................................................... 63 3.2 Objective ......................................................................................................................... 63 3.3 Definition and Standards .................................................................................................. 64 3.3.1 Classroom acoustics .............................................................................................................. 64 3.3.2 Industrial workroom acoustics .............................................................................................. 67 3.4 Materials and Methods .................................................................................................... 68 3.4.1 Background noise levels (BNL) .............................................................................................. 68 3.4.2 Reverberation times (RT) ...................................................................................................... 69 3.4.3 Speech intelligibility index (SII) ............................................................................................. 70 3.4.4 Reduction of sound level with distance doubling (DL2) ........................................................ 71 3.4.5 Data and results analysis ....................................................................................................... 72 3.5 Results ............................................................................................................................. 74 3.5.1 TES design and settings ......................................................................................................... 74 3.5.2 Background-Noise Levels (BNL) ............................................................................................. 76 3.5.3 Reverberation time (RT) ........................................................................................................ 83 3.5.4 Speech intelligibility index (SII) ............................................................................................. 90 3.5.5 Reduction of sound level with distance doubling (DL2) ........................................................ 94 3.6 Discussion ........................................................................................................................ 95 3.6.1 Background noise levels (BNLs) ............................................................................................. 96 3.6.2 Reverberation time ............................................................................................................. 100 3.6.3 Speech intelligibility index (SII) ........................................................................................... 103 3.6.4 Reduction of sound levels with distance doubling (DL2) ..................................................... 104 3.7 Summary ....................................................................................................................... 105 4 Evaluation of the Student and Teacher Exposure to Noise and Airborne Hazards ........ 107 4.1 Introduction .................................................................................................................. 107 4.2 Objective ....................................................................................................................... 107 4.3 Hazard exposure limits ................................................................................................... 108 4.3.1 Noise in TES ......................................................................................................................... 108 4.3.2 Wood dust in TES ................................................................................................................ 108 4.3.3 Welding fume in TES ........................................................................................................... 109 4.4 Materials and methods .................................................................................................. 109 4.4.1 Evaluation of the personal exposure to noise in TES .......................................................... 110 4.4.2 Evaluation of the exposure to wood dust in TES ................................................................ 111 4.4.3 Evaluation of the exposure to welding fume in TES ........................................................... 114 4.5 Indoor air quality ........................................................................................................... 116 4.6 Data and results analysis ................................................................................................ 116 4.7 Results ........................................................................................................................... 118 4.7.1 Noise personal exposure level ............................................................................................ 118 4.7.2 Exposure to wood dust in woodworking TES ...................................................................... 125 4.7.3 Exposure to welding-fume in metalworking and automotive TES ...................................... 130 5 Inclusive Discussion of the Evaluation Results............................................................. 134   vii 5.1 Introduction .................................................................................................................. 134 5.2 Occupational exposure to noise and airborne hazards .................................................... 135 5.2.1 Exposure to noise ................................................................................................................ 135 5.2.2 Exposure to wood dust ....................................................................................................... 144 5.3 Summary discussion of synthesis .................................................................................... 151 5.3.1 Impact of the conflicts in TES design/settings on teachers’ and students’ exposures ....... 152 5.3.2 Impact of responsibilities-roles of teaching and working on the health and safety of teachers and students. ..................................................................................................................... 154 5.4 Challenges of establishing specific exposure limits for students/children ......................... 156 5.5 Summary ....................................................................................................................... 157 6 Acoustics and Airborne Hazard Control in TES ............................................................ 160 6.1 Introduction .................................................................................................................. 160 6.2 Objective ....................................................................................................................... 161 6.3 Acoustics and noise control measures in TES................................................................... 161 6.3.1 General principles of room acoustics and noise control ..................................................... 161 6.3.2 Suggested noise control measures in TES ........................................................................... 168 6.3.3 Hearing conservation program (HCP) for teachers and students ....................................... 182 6.4 Airborne hazard control measures in TES ........................................................................ 184 6.4.1 General principles ............................................................................................................... 185 6.4.2 Suggested methods to control exposure to wood dust ...................................................... 191 6.4.3 Suggested control measures to eliminate exposure to welding fumes .............................. 197 6.5 Student and teacher behavior control in TES ................................................................... 202 6.6 Discussion of control measures and possible conflicts/limitations ................................... 205 6.6.2 Crucial factors and limitations of installing hoods for exhaust systems ............................. 207 6.6.3 Crucial factors and limitations of using HPDs and RPEs ...................................................... 210 6.6.4 Limitations and needs in implementing Hearing Conservation Program on students ....... 214 6.7 Summary ....................................................................................................................... 217 7 Conclusion ................................................................................................................. 220 7.1 Overview ....................................................................................................................... 220 7.2 Objectives and key empirical findings ............................................................................. 220 7.3 Scientific contributions .................................................................................................. 221 7.3.1 Evaluation of the acoustical conditions and Conflicts in TES (Chapter 3) ........................... 222 7.3.2 Occupational exposure to noise and airborne hazards in TES (Chapter 4) ......................... 223 7.3.3 Acoustics and occupational hazard controls in TES (Chapter 6) ......................................... 225 7.4 Limitations and strengths ............................................................................................... 226 7.4.1 Limitations in conducting exposure evaluation of teachers and students in school TES ... 226 7.4.2 Strengths ............................................................................................................................. 229 7.5 Research implications .................................................................................................... 231 7.5.1 Exposure evaluation methods for students and teachers in schools ................................. 231 7.5.2 Acoustical controls and exposure reduction ....................................................................... 232 7.5.3 Stakeholders who should be at the table in relation to actions that arise from the study 234 7.6 Future directions............................................................................................................ 235 7.6.1 Noise and acoustical characteristics and performance/health studies .............................. 235 7.6.2 Exposure to wood dust and welding fume and health effect studies ................................ 236 7.6.3 Control measures, safety policies and safe work practice evaluation studies ................... 237 7.7 Conclusion ..................................................................................................................... 238   viii   REFERENCES ...................................................................................................................... 239 APPENDIX A ...................................................................................................................... 257 APPENDIX B ....................................................................................................................... 260 APPENDIX C ....................................................................................................................... 261 APPENDIX D ...................................................................................................................... 270 APPENDIX E ....................................................................................................................... 271 APPENDIX F ....................................................................................................................... 276 APPENDIX G ...................................................................................................................... 279     ix  List of Tables  TABLE 1.1: NUMBER OF HIGH SCHOOLS AND TES IN FOUR SCHOOL DISTRICTS IN THE GREATER VANCOUVER IN BRITISH COLUMBIA. ......... 4 TABLE 1.2: WOOD TYPES AND EXAMPLES OF SPECIES AVAILABLE OR USED IN TES (BEAN ET AL., 2006). ........................................... 29 TABLE 1.3: EXAMPLE OF WOOD SPECIES AND RELATED ADVERSE HEALTH EFFECTS (HSE, 2012)....................................................... 29 TABLE 1.4: WOOD DUST ASSOCIATED ACUTE AND CHRONIC HEALTH EFFECTS (MILHAM, 1974; IARC, 1995; DEMERS ET AL., 1995; ANDERSEN ET AL., 1977; HSE, 2012; NTP, 2000; NIOSH, 2011). .............................................................................. 30 TABLE 1.5: TYPE OF ARC WELDING AND METAL AND THE RELATED HEAVY METALS AND GASES (WHS, 2009; OSHA, 2013; PERKINS, 2008; SHANE ASHBY, 2002; BROWN JR, 2012). ........................................................................................................ 36 TABLE 1.6: HEALTH EFFECTS OF WELDING FUME HEAVY METALS AND GASES (OSHA, 2013; WHS, 2009; ACGIH, 2013). ................ 37 TABLE 2.1: INVESTIGATED TES TYPES AND NUMBERS IN EACH SCHOOL DISTRICT. .......................................................................... 60 TABLE 2.2: CHARACTERISTICS AND CONSTRUCTIONS OF THE TWENTY-SIX TES. ............................................................................. 61 TABLE 3.1: MAXIMUM A-WEIGHTED STEADY BACKGROUND NOISE LEVELS (BNL) AND MAXIMUM REVERBERATION TIMES (RTS) IN UNOCCUPIED, FURNISHED LEARNING SPACES (ANSI S12.60-2009). ................................................................................ 65 TABLE 3.2: PROPOSED SPEECH INTELLIGIBILITY INDEX (SII) AND SPEECH-INTELLIGIBILITY (SI) QUALITY CRITERIA (EN-ISO9921 - 2003). . 66 TABLE 3.3: MINIMUM DL2 (IN DB/DISTANCE DOUBLING) CRITERIA FOR LA,TOT IN UNOCCUPIED, FITTED-  INDUSTRIAL ROOMS AS A FUNCTION OF FLOOR AREA, S (ONDET & SUEUR, 1994). ................................................................................................ 67 TABLE 3.4: VARIATION OF ROOM-AVERAGE BACKGROUND NOISE LEVELS (BNL, DBA) FOR UNOCCUPIED AND OCCUPIED TES IN DIFFERENT CONDITIONS. .......................................................................................................................................................... 77 TABLE 3.5: MAJOR DETERMINANTS OF BACKGROUND NOISE LEVELS IN ALL UNOCCUPIED TES WHEN VENTILATION SYSTEM ONLY ON. ...... 78 TABLE 3.6: TES TASKS AND TOOLS NOISE LEVELS (DBA) AND PROCESS DURATION (MINUTES). ......................................................... 82 TABLE 3.7: REVERBERATION TIMES (RT) FOR UNOCCUPIED TES AND CALCULATED DESCRIPTIVE QUANTITIES ACCORDING TO DIFFERENT CONDITIONS OF TES. ............................................................................................................................................... 85 TABLE 3.8: MAJOR DETERMINANTS RELATED TO REVERBERATION TIMES RT. ................................................................................ 87 TABLE 3.9: SPEECH INTELLIGIBILITY INDEX (SII) AND SPEECH-INTELLIGIBILITY QUALITY (SIQ) VALUES FOR THREE UNOCCUPIED TES WITH VENTILATION SYSTEM ONLY IN OPERATION, AS A FUNCTION OF VOCAL OUTPUT, AT THREE DIFFERENT DISTANCES FROM THE SPEECH SOURCE. ................................................................................................................................................................ 91 TABLE 3.10: ROOM-AVERAGE SPEECH INTELLIGIBILITY INDEX (SII), SPEECH-INTELLIGIBILITY QUALITY (SIQ) AND PASS (P)/FAIL (F) RATINGS FOR TWENTY UNOCCUPIED TES WITH VENTILATION SYSTEM ONLY IN OPERATION, AS A FUNCTION OF VOCAL OUTPUT. ..... 92 TABLE 3.11: ROOM-AVERAGE SPEECH INTELLIGIBILITY INDEX (SII), SPEECH-INTELLIGIBILITY QUALITY (SIQ) AND PASS (P)/FAIL (F) RATINGS FOR TEN TES WHEN OCCUPIED AND IN NORMAL OPERATION, AS A FUNCTION OF VOCAL OUTPUT. ............................... 93 TABLE 3.12: MEASURED DL2 VALUES (IN DB/DISTANCE DOUBLING) AND PASS/FAIL RATINGS IN TWENTY TES AND COMPARISON WITH ONDET & SUEUR (1995) ACCEPTABILITY/DESIGN CRITERIA. ............................................................................................ 95 TABLE 4.1: NUMBER OF RECRUITED TES, TEACHERS AND STUDENTS. ........................................................................................ 110 TABLE 4.2: VARIATION OF NOISE EXPOSURE LEVELS AMONG TEACHERS AND STUDENTS WITH THE DESCRIPTIVE CHARACTERISTICS ACCORDING TO DIFFERENT TYPES OF TES. .................................................................................................................. 120 TABLE 4.3: TEACHERS INHALABLE WOOD DUST EXPOSURE CONCENTRATIONS IN NINE WOODWORK TES. ......................................... 126 TABLE 4.4: DESCRIPTIVE RESULTS OF DAILY PERSONAL EXPOSURE TO INHALABLE WOOD DUST IN NINE TES. ...................................... 126 TABLE 4.5: STUDENTS INHALABLE WOOD DUST EXPOSURE LEVELS IN NINE OCCUPIED WOODWORK TES. .......................................... 127 TABLE 4.6: WOOD-DUST AREA CONCENTRATIONS IN NINE WOODWORK TES. ............................................................................ 128 TABLE 4.7: WOOD-DUST CONCENTRATIONS (TOTAL DUST) GENERATED FROM SPECIFIC WOODWORKING TOOLS AND MACHINES IN WOODWORK TES.................................................................................................................................................. 129 TABLE 4.8: WELDING-FUME PERSONAL EXPOSURE OF ONE TEACHER AND THREE STUDENTS IN THREE OCCUPIED METAL AND ONE AUTOMOTIVE TES (SAMPLES COLLECTED DURING WELDING ONLY). ................................................................................. 131 TABLE 4.9: WELDING-FUME AREA CONCENTRATIONS IN THREE OCCUPIED METAL AND AUTOMOTIVE TES. ....................................... 132 TABLE 4.10: CONCENTRATIONS OF CO2 AND NUMBER OF OCCUPANTS IN EACH TES AS COMPARED WITH STANDARD. ....................... 133 TABLE 5.1: CONTROL MEASURES, TASKS AND EXPOSURE CONDITIONS INVESTIGATED IN 17 OCCUPIED TES IN BRITISH COLUMBIA. ....... 137 TABLE 6.1: RECOMMENDED MINIMUM DUCT VELOCITIES AND EXHAUST FLOW RATES FOR WOODWORKING MACHINES IN TES (ACGIH, 2007). ............................................................................................................................................................... 192    x List of Figures   FIGURE 1.1: A LARGE WOODWORK TES IN BURNABY IN BC. ..................................................................................................... 12 FIGURE 1.2: METALWORK TES IN SURREY IN BC. ................................................................................................................... 15 FIGURE 1.3: WELDING ZONE IN A METALWORK TES IN RICHMOND IN BC. ................................................................................... 15 FIGURE 1.4: AUTOMOTIVE TES IN RICHMOND IN BRITISH COLUMBIA. ........................................................................................ 16 FIGURE 1.5: HIERARCHY CONTROL MEASURES (NIOSH, 2015; CCOHS, 2015; HSE,2015). ........................................................ 56 FIGURE 1.6: THESIS STRUCTURE BASED ON THE INDUSTRIAL HYGIENE FRAMEWORK OF EVALUATION AND CONTROL OF EXPOSURE TO HAZARDS. .............................................................................................................................................................. 57 FIGURE 2.1: FLOOR PLAN OF WOODWORK TES IN BURNABY. .................................................................................................... 62 FIGURE 2.2: FLOOR PLAN OF METALWORK TES IN SURREY. ...................................................................................................... 62 FIGURE 3.1: A FLOOR PLAN OF A WOODWORK TES. ALSO SHOWN THE POSITIONS AT WHICH LOUD SPEAKERS, SOUND LEVEL METER, AND SPEECH SOURCE WERE LOCATED FOR THE ACOUSTICAL MEASUREMENTS. ............................................................................ 73 FIGURE 3.2: MEASURING DL2  IN UNOCCUPIED METALWORK TES. FIGURE SHOWS SOUND LEVEL METER (IN YELLOW CIRCLE), AND AN OMNI LOUDSPEAKER (IN RED CIRCLE). THE DISTANCE WAS 8 METER BETWEEN EACH OF THEM. ............................................... 73 FIGURE 3.3: MEASURED TOTAL, A-WEIGHTED ROOM-AVERAGE BACKGROUND NOISE LEVELS (BNL IN DBA) IN TWENTY-SIX UNOCCUPIED TES WITH VENTILATION SYSTEMS ONLY IN OPERATION. ALSO SHOWN ARE THE ANSI S12.60-R2009 CRITERIA FOR CLASSROOMS (BNL ≤ 35 OR 40 DBA, DEPENDING ON ROOM ............................................................................................................ 76 FIGURE 3.4: ROOM–AVERAGE TOTAL, A-WEIGHTED BACKGROUND-NOISE LEVELS (BNL IN DBA) IN THIRTEEN UNOCCUPIED TES WITH VENTILATION SYSTEMS ON, AND DUST COLLECTORS ON AND OFF. ALSO SHOWN ARE THE ANSI CRITERIA FOR CLASSROOMS (BNL ≤ 35 OR 40 DBA, DEPENDING ON ROOM VOLUME). ......................................................................................................... 78 FIGURE 3.5: MEASURED BACKGROUND NOISE LEVELS (BNL IN DBA) AT OCTAVE-BAND FREQUENCIES (125 HZ-8 KHZ) IN TWO UNOCCUPIED LARGE TES WITH VENTILATION SYSTEMS ONLY ON. ALSO SHOWN ARE THE ANSI CRITERIA FOR CLASSROOMS (BNL ≤ 35 OR 40 DBA DEPENDING ON ROOM VOLUME). .......................................................................................................... 79 FIGURE 3.6: MEASURED BACKGROUND NOISE LEVELS (BNL IN DBA) AT OCTAVE-BAND FREQUENCIES (125 HZ-8 KHZ) IN UNOCCUPIED LARGE WOODWORK TES  (WS1) WITH VENTILATION SYSTEMS ON, AND DUST COLLECTORS ON AND OFF. ALSO SHOWN ARE THE ANSI CRITERIA FOR CLASSROOMS (BNL ≤ 35 OR 40 ...................................................................................................... 80 FIGURE 3.7: ROOM-AVERAGE TOTAL, A-WEIGHTED BACKGROUND-NOISE LEVELS (BNL IN DBA) IN SEVENTEEN TES WHEN UNOCCUPIED (VENTILATION SYSTEM ONLY IN OPERATION), AND OCCUPIED AND IN NORMAL OPERATION. ALSO SHOWN ARE THE ANSI CRITERIA FOR CLASSROOMS (BNL ≤ 35 OR 40 DBA, DEPENDING ON ROOM VOLUME) (ANSI, 2009). ................................................. 81 FIGURE 3.8: MEASURED ROOM-AVERAGED MID-FREQUENCY REVERBERATION TIMES (RT IN S) IN TWENTY UNOCCUPIED TES. ALSO SHOWN ARE THE CRITERIA FOR CLASSROOMS (RT ≤ 0.6, ≤ 0.7 S) AND INDUSTRIAL WORKSHOPS (RT ≤ 1 S). ........................................ 84 FIGURE 3.9: VARIATION OF RT WITH CEILING HEIGHT. ............................................................................................................. 85 FIGURE 3.10: VARIATION OF RT WITH SOUND ABSORBING MATERIALS. ....................................................................................... 86 FIGURE 3.11: MEASURED OCTAVE-BAND REVERBERATION TIMES (RT IN S) IN THREE DIFFERENT TYPES OF TES: METAL TES, WOOD TES, AND AUTOMOTIVE TES IN RICHMOND SCHOOL DISTRICT. ALSO SHOWN IS THE WARNOCK 1-S AND ANSI 0.7-S CRITERIA FOR UNOCCUPIED CONDITIONS. ........................................................................................................................................ 88 FIGURE 3.12: MEASURED OCTAVE-BAND REVERBERATION TIMES (RT IN S) IN TWO DIFFERENT TYPES OF TES: WOOD TES, AND AUTOMOTIVE TES IN BURNABY SCHOOL DISTRICT. ALSO SHOWN IS THE WARNOCK 1-S AND ANSI 0.7-S CRITERIA FOR UNOCCUPIED CONDITIONS. .......................................................................................................................................................... 88 FIGURE 3.13: MEASURED OCTAVE-BAND REVERBERATION TIMES (RT IN S) IN A METALWORK TES, IN BURNABY SCHOOL DISTRICT. ALSO SHOWN IS THE WARNOCK 1-S CRITERION FOR UNOCCUPIED CONDITIONS. .......................................................................... 89 FIGURE 3.14: MEASURED OCTAVE-BAND REVERBERATION TIMES (RT IN S) IN A METALWORK TES AND A WOODWORK TES, IN SURREY SCHOOL DISTRICT. ALSO SHOWN IS THE WARNOCK 1-S CRITERION FOR UNOCCUPIED CONDITIONS. .......................................... 89 FIGURE 3.15: MEASURED TOTAL, A-WEIGHTED SOUND-PRESSURE LEVEL (SPL IN DBA) SPATIAL-DECAY CURVE FOR A WOOD TES (WB1), WITH LOGARITHMIC REGRESSION LINE AND EQUATION, CORRESPONDING TO DL2 = 2.9 DB/DISTANCE DOUBLING. ...................... 94 FIGURE 3.16: AN IMAGE OF THE OLD WS4 TES. THIS SHOWS A WIDE VIEW OF THE TES AND THE TYPE OF HIGH CEILING IN ONE PART OF THE ROOM. .......................................................................................................................................................... 102    xi FIGURE 3.17: AN IMAGE OF THE OLD WS4 TES. THIS SHOWS THE TYPE OF LOW CEILING IN THE MIDDLE SECTION OF THE ROOM. ......... 102 FIGURE 4.1: AVERAGE PERSONAL NOISE EXPOSURE (LAEQ, 6 HR, DBA) AMONG SEVENTEEN TES TEACHERS. ALSO SHOWN ARE THE CORRECTED LIMIT OF EXPOSURE ≤ 86 DBA/6-HOURS AND THE ACTION LEVEL 82 DBA (WORK SAFE OF BC, 1996). ................ 119 FIGURE 4.2: AVERAGE PERSONAL NOISE EXPOSURE LEVELS (LAEQ-1HR, DBA) FOR SEVENTEEN TES STUDENTS. ALSO SHOWN ARE THE CORRECTED LIMIT OF EXPOSURE ≤ 94 DBA/1-HOUR AND THE ACTION LEVEL 82 DBA  (WORK SAFE OF BC, 1996). ................. 119 FIGURE 4.3: WS2 TES TEACHER NOISE EXPOSURE LEVEL ON THE FIRST DAY OF SAMPLING. ........................................................... 121 FIGURE 4.4: WS2 TES TEACHER NOISE EXPOSURE LEVEL ON THE SECOND DAY OF SAMPLING. ........................................................ 121 FIGURE 4.5: MR4 TES TEACHER NOISE EXPOSURE LEVEL ON THE FIRST DAY OF SAMPLING. ........................................................... 122 FIGURE 4.6: MR4 TES TEACHER NOISE EXPOSURE LEVEL ON THE SECOND DAY OF SAMPLING. ....................................................... 123 FIGURE 4.7: MS3 TES STUDENT NOISE EXPOSURE LEVELS ON THE FIRST DAY OF SAMPLING. .......................................................... 124 FIGURE 4.8: AB1 TES STUDENT NOISE EXPOSURE LEVELS ON ONE DAY OF SAMPLING. .................................................................. 124 FIGURE 6.1: DIAGRAM OF VENTILATION SYSTEM COMPONENTS AND FEATURES (SMITH ET AL., 1996). ........................................... 165 FIGURE 6.2: SCHEMATIC DIAGRAM OF FAN AND DUCT, DEMONSTRATING SOME OF THE   NOISE TRANSMISSION PATHS IN THE BUILDING (SMITH EL AT., 1996). ........................................................................................................................................... 166 FIGURE 6.3: AN ILLUSTRATION OF ABSORPTIVE DUCT SILENCER COMPONENT. ............................................................................. 170 FIGURE 6.4: SOUND PROOF DUCT LAGGING/WRAP MATERIAL. IMAGE SOURCE: HTTP://WWW.SOUNDCONTROLSERVICES.CO.UK/ ........ 170 FIGURE 6.5: ACOUSTIC DUCT/PIPE LAGGING AND WRAP. IMAGE SOURCE: HTTP://WWW.PIPEANDDUCT.COM/ ................................. 170 FIGURE 6.6: VENTILATION SYSTEM PIPES IN WOODWORKING SHOP WS3 THAT CAN BE WRAPPED WITH LAGGING MATERIALS TO REDUCE THE TRANSMISSION OF VENTILATION NOISE TO THE TES. ............................................................................................... 171 FIGURE 6.7: VENTILATION SYSTEM DUCTS IN AUTOMOTIVE SHOP AB1 THAT CAN BE WRAPPED WITH DUCT LAGGING MATERIALS TO REDUCE THE TRANSMISSION OF VENTILATION NOISE TO THE TES. ............................................................................................... 171 FIGURE 6.8: A DUST COLLECTOR EXHAUST SILENCER AND ITS COMPONENTS. .............................................................................. 172 FIGURE 6.9: DUST COLLECTOR PIPES IN WOODWORK SHOP WB2 THAT CAN BE WRAPPED WITH LAGGING MATERIALS TO REDUCE THE TRANSMISSION OF DUST COLLECTOR NOISE TO THE TES. ............................................................................................... 173 FIGURE 6.10: DUST COLLECTOR PIPES IN WOODWORK SHOP WR2 THAT CAN BE WRAPPED WITH LAGGING MATERIALS TO REDUCE THE TRANSMISSION OF DUST COLLECTOR NOISE TO THE TES ................................................................................................ 173 FIGURE 6.11: SHOP VACUUM ENCLOSURE TO REDUCE VACUUM NOISE. ..................................................................................... 174 FIGURE 6.12: MACHINES WHERE NOISE/VIBRATION DAMPING MATERIALS SHOULD BE ADDED TO REDUCE TRANSMITTED NOISE OF MACHINE MOTOR IN WS3. ................................................................................................................................................... 175 FIGURE 6.13: MACHINES WHERE NOISE/VIBRATION DAMPING MATERIALS SHOULD BE ADDED TO REDUCE TRANSMITTED NOISE OF MACHINE MOTOR IN WB1. .................................................................................................................................................. 176 FIGURE 6.14: ACOUSTICAL CEILING BAFFLES IN INDUSTRIAL WORKSHOP. ................................................................................... 178 FIGURE 6.15: ACOUSTICAL CEILING PANELS (QUIET CLOUD) IN BOTTLE FACTORY. ........................................................................ 178 FIGURE 6.16: LOCATIONS SUGGESTED TO MOUNT ACOUSTICAL PANELS TO THE CEILINGS OF A WOODWORKING TES (WS3) AS AN ADDITIONAL METHOD TO REDUCE HIGH BNL AND RTS. ................................................................................................. 179 FIGURE 6.17: MAJOR TYPES OF EXHAUST HOODS (OPEN AND ENCLOSED) AND INSTALLATION LOCATIONS OF EXHAUST SYSTEM HOODS (ACGIH, 1995; ACGIH, 2007). ............................................................................................................................ 189 FIGURE 6.18: EXHAUST SYSTEM HOODS LOCATION AND CAPTURE VELOCITY AS ........................................................................... 190 FIGURE 6.19: DUST COLLECTOR HOOD INSTALLATION LOCATION FOR TABLE SAW (ACGIH, 1995). ................................................ 190 FIGURE 6.20: ILLUSTRATION OF AUXILIARY EXHAUST HOOD AND DIVIDER PLATE FOR TABLE SAWS (NIOSH, 1996). ........................... 193 FIGURE 6.21: ORBITAL HAND-SANDER CONNECTED TO EXTERNAL WOOD DUST EXTRACTION SYSTEM. KEY: A. DUST EXTRACTOR; B. ADAPTER FOR CONNECTION OF SANDER; C. COMPRESSED AIR SUPPLY LINE; D. NOISE SILENCER; E. EXTRACTED DUST TUBE; F. EXHAUST AIR TUBE; G. FLEXIBLE HOSE; H. ORBITAL SANDER (THORPE AND BROWN, 1994). ................................................ 194 FIGURE 6.22: ILLUSTRATION FOR DUST CONTROL PLENUM FOR ORBITAL SANDERS (NIOSH, 1996). ............................................... 195 FIGURE 6.23: STUDENT WELDING IN AN AUTOMOTIVE TES AND WEARING WELDING HELMET WITHOUT RESPIRATOR. ........................ 200 FIGURE 6.24: WELDING HELMET WITH BUILT IN RESPIRATOR AND FILTERS UNITS. ........................................................................ 201         xii  List of Symbols and Abbreviations    % Percent © Registered trademark ACGIH American Conference Government of Industrial Hygiene   acfm Actual air-  cubic foot per meter AFSCME American Federation of State, County and Municipal Employees  ANSI American National Standard Institute ASA American Society of Acoustics Avg. Average BC British Columbia BNL Background Noise Levels CCOHS Canadian Centre for Occupational Health and Safety CEN European Committee for Standardization (Comité Européen de Normalisation) cfm Cubic foot per minute dB Decibels dBA Decibels with A weighting  DL2 Reduction of sound levels by doubling distance  fpm Foot per minute HSE Health and Safe Executive   xiii IARC International Agency for Research on Cancer ILO International Labour Organization ISO International Organization for Standardization Leq,a Equivalent continuous A-weighted sound pressure level  Lex Noise exposure level LOD Limit of detection mg/m3 milligram per cubic meter MSDS Material Safety Data Sheet NIH National Institute of Health NIOSH National Institute for Occupational Safety and Health NTP National Toxicology Program OROSHA Oregon Occupational Safety and Health Organization OSHA Occupational Safety and Health Organization OEL Occupational exposure limit RT Reverberation time SD Standard deviation  SII Speech intelligibility index SIQ Speech intelligibility quality STEL Short term exposure limit TES Technology educational shops TLV Threshold limit value TWA Time weighted average    xiv WHMIS Workplace Hazardous Materials Information System WHO World Health Organization WHS Workplace Health and Safety                          xv Acknowledgments  First, I would like to offer my sincere gratitude to my advisor Prof. Murray Hodgson for the continuous support of my PhD study and related research, for his patience, motivation, and immense knowledge. His supervision helped me throughout the research and writing of this thesis.  In addition, I would like to thank the rest of my thesis committeeProf. Karen Bartlett, Prof. Mieke Koehoorn, and Dr. Hugh Daviesfor their support and insightful comments throughout the conduct and reporting of this research, which guided me to broaden my research from various perspectives. I heartily thank WorkSafeBC for their grant support to conduct this research.   My sincere thanks also goes to the members of Acoustics and Noise Research Group – in particular, Shira Daltrop – for assistance during acoustical measurements.  Many thanks to SOEH laboratory manager Matthew Jeronimo for his assistance with sampling-equipment preparation, and for giving me access to the laboratory.  I also would like thank the school districts and school principals in Richmond, Burnaby, and Surrey for their approval to conduct this study in their high schools. My sincere thanks also goes to each TES teacher who kindly participated in this research, and thanks to the parents who gave permission for their kids to participate as well. Without their precious participation, it would not be possible to conduct this research.    xvi Special thanks to my University in Saudi Arabia – King Abdul Aziz University – for scholarship and the financial support throughout my entire period of stay and study in Canada.   Last, but not the least, I would like to express my genuine thanks to my family – my parents, my wife and to my sisters – for supporting and encouraging me spiritually with love and care throughout writing this dissertation and my life in general.                             xvii   Dedication      To my parents,  To young workers & TES teachers The reason of what I       1 1 Introduction   This chapter provides an introduction to the main concepts and framework elements of the dissertation. This study mainly focuses on the evaluation of the work and learning quality in high-school Technology Educational Shops, and the evaluation of the occupational exposures to noise and airborne hazards among teachers and students. This introduction is presented through seven related sections.  The first sections are the research general background, and a summary about Technology Educational Shops (TES) including background, description of the occupants, design and settings, TES teachers’ roles, and the nature of teaching and working in TES, with a brief description of three specific types of TES. Sections 2 and 3 illustrate the major conflicts that are associated with the design of TES and with working and teaching in TES among teachers and students, and discuss the hazards of most interest. Section 4 summarizes the existing literature related to this project and discusses the gaps in previous studies. Consequently, section 5 presents factors and reasons that motivated the researcher to conduct this project, in addition to the general aim of the study. This is followed by the objectives and the overview of the thesis in sections 6 and 7, respectively.   Information in this chapter is based on the data collected and from reviewing the literature, as well as from pre-visits and walk-throughs of TES, and from meeting with school representatives.      2  1.1 Research background Around the world, there are 250,000,000 young workers of age less than 25 years old working in different trades and industries.  Many of them are children of ages between 5 and 17 years old.  Statistics suggest that about 70% of them have been facing dangerous work conditions. These conditions include their exposure to different kinds of workplace hazards that have significant effects on their health, physically and psychologically, in the short and the long term (ILO, 2002).  In fact, young workers are significantly vulnerable to occupational hazards, injuries or illness (CCOHS, 2015).  Across Canada, hundreds of young workers are injured or killed in the workplace every year. For instance, about 90 young workers died in the workplace in the year 2006 (Government of Canada, 2015).  In British Columbia, WorkSafeBC indicated that there are more than 350,000 young workers (< 24 years old) that work in different types of workplaces (e.g. retail stores, construction sites, and in industrial workshops) and they face 48% higher risk of injuries than the overall working population.  In fact, during the period between 2008-2012, there were around 37,000 young workers who were injured and had time loss claims, and about 8,000 were seriously injured. Researchers also found that the major practical reasons for these higher rates of injuries include that young workers are risk-takers, they lack work experience, knowledge, training and supervision, and they work with more workplace hazards, that they are unfamiliar with (WorkSafeBC, 2011).   All these statistics represent paid (employed) young workers in regular workplaces only, which are under the umbrella of local workplace regulatory entities such as the WorkSafeBC   3 and the Ministry of Labor in British Columbia. In other words, these workers are guided by legislated working safety regulations and special standards to control their occupational exposure to hazards.  Now if this is the situation among those employed young workers, what will be the case for the pre-employed students in high school Technological Educational Shops, who are learning, working and are exposed to workplace hazards at the same time.  Although their safety is under the responsibility of the Ministry of Education, they are not totally guided or protected by any special regulations addressing the special characteristics of TES, or are even being monitored by professional inspectors. In fact, many of their teachers who are under the protection of WorkSafeBC may not be familiar with all workplace hazards or how to monitor and control the individuals’ exposure from the industrial hygiene point of view. Part of this job is related to the health and safety inspector designated from the association at each school district but often is only active in cases of incidence/accidents. Consequently, this can put both the student and the teacher at risk of exposure to many hazards in TES, which could adversely affect their health and education quality.  Therefore, conducting this pilot study will explore and investigate the work and control conditions in these unique learning and working environments.    1.2 Technology educational shops 1.2.1 Background, definition and objective The Ministry of Education in British Columbia has developed career and technical education programs for high school students to provide them with greater choice and flexibility in   4 selecting courses that meet their education and profession goals. It is the path to build a career and find opportunities to be a part of an active and challenging society. It allows students to learn how to design and construct solutions to real-world problems, and opportunities to practice what they have learned in classes. Therefore, Technology Education Shops (TES) have been built in high schools; they are small-scale industrial shops where students have the opportunity to solve technological problems, build technical products (e.g., robotics, woodwork, and metalwork products), develop appropriate attitudes and practices with respect to work safety and personal health, and to develop all required skills to investigate aspects of technology (British Columbia Ministry of Education, 2001). In TES, teachers work and teach high school students from grades 8 to 12 (12 – 18 years old) who should learn technical skills effectively and safely, without detrimental effects to their health.  Different kinds of TES are provided to the students, including automotive, woodwork, metalwork, mechanics, electronics and robotics, carpentry and joinery, furniture, drafting and design, creative wood art metal, general technology TES, trans power and energy TES (British Columbia Ministry of Education, 2001). Table 1.1 shows number of high schools and TES in four school districts in the Greater Vancouver in British Columbia.   Table 1.1: Number of high schools and TES in four school districts in the Greater Vancouver in British Columbia. School District Number of High Schools  Number of TES in Each School District Surrey 25 ≈ 60 Vancouver 18 ≈ 32 Burnaby 8 ≈ 22 Richmond 10 28    5 1.2.2 General description of TES design and settings TES are designed to be real industrial workrooms in many cases, including the installation of all required industrial machines and equipment, and to assure the provision of the needed environmental control measures for a healthy and safe work environment.  Generally, they are constructed with concrete floors and walls, and metal ceilings, which in some cases are treated with acoustical materials. Ceilings in most of these TES are high, and the TES have wide or long floor areas. Local dust collectors are installed and operated, along with ventilation and industrial-purpose fans.  They are much different in design and settings from regular classrooms or general learning environments, which are smaller in size and have desks and chairs, carpeted floors, acoustical ceilings tiles, and no loud ventilation and dust collection systems. Regular classrooms are mainly designed to be comfortable and acoustically acceptable for good learning.    However, local TES are not typical classrooms and their designs may not be conductive to learning.  It is important to mention that TES are used as classrooms for learning and teaching and as industrial workshops for working and building things at the same time. These two different purposes could require different room settings and designs for suitable learning and working outcomes. A teaching ‘classroom’ zone is always a part of the TES. But it varies in design; it is often open to the general industrial zone–in some cases, this teaching zone could have a lower ceiling than the industrial area, or could be totally isolated from the work area or located on the upper floor of the TES. Each TES could contain an office for the teacher, which is a part of the TES or sometimes separated in an adjacent area.    6 These differences in uses and settings result in serious conflict issues regarding teaching and working in these unique environments, as will be discussed in the next sections.  1.2.3 Health and safety in TES: Responsibilities  The health and safety of TES teachers is the responsibility of the School District Board and the assigned committees and departments as stipulated by WorkSafeBC regulations.  The health and safety of the TES students and their well-being is the responsibility of the School District and the TES teachers (British Columbia Ministry of Education, 2002). 1.2.3.1 School districts School districts act as employers who have to provide safe work environments, take immediate action when a teacher or supervisor reports about a potentially hazardous condition in the TES, conduct immediate inspections, report inspected conditions and accidents to WorkSafeBC, provide adequate First Aid facilities and services, and provide the required personal protective equipment (British Columbia Ministry of Education, 2002).  The district board of each school understands that teachers have the right to work and teach in safe, clean and healthy workplaces.  These teachers are only expected to work in environments where the temperature, humidity, ventilation, lighting, sound level, dust level and other physical conditions are hygienic and meet health and safety standards.   The Health and Safety Committees of the school districts have to assist in creating a safe and healthful workplace for teachers and their students.  In general, they have to determine that regular inspections of the place “TES” safety and health conditions are carried out by the health and safety officers/inspectors of the district as required by WorkSafeBC regulations,   7 determine the provisions of safety and health services, recommend measures required to attain compliance with the School Act and the Occupational Health and Safety Regulations of WorkSafeBC, correct hazardous conditions as soon as feasible, and submit the required reports and documentation promptly.   The School District Health and Safety officer performs regular inspection of the hygiene conditions and safety in the TES.  This task involves the review all workplace safety procedures related to tools and machines operating, review and investigate of all serious accidents/incidents and report the audit results to the committee to take the required action. In addition, this inspector’s work could include or support the promotion of health and safety awareness, and ensure that school district standards of occupational health are in compliance with the current WorkSafeBC regulations. 1.2.3.2 TES teachers’ qualifications and roles/responsibilities TES teachers in the Canadian province of British Columbia are certified teachers with a university degree and a Technology Teacher Education (TTED) diploma from BCIT.  The TTED program is a joint program between the University of British Columbia (UBC) and British Columbia Institute of Technology (BCIT).  This program is a combination of three components: 1) academic component (30 credits of university transfer liberal arts and science courses, and six credits of English; 2) technological component (completion of two-year diploma of TTED at BCIT); 3) instructive/teaching component (completion of professional teacher education at UBC).  After qualifying, TES teachers have the ability to work in middle- and high-school systems in British Columbia.  They also go out for job training in actual TES of their specialties, and   8 sometimes in a particular school that has a place for a new teacher or assistant (British Columbia Institute of Technology, 2015).  In 2002, the Ministry of Education (Curriculum Branch), the Technology Education Association and WorkSafeBC (Workers’ Compensation Board of BC), developed an instructional safety handbook: “HEADS Up! for Safety” for TES teachers.  The goal was to create a standard guide for occupational health and safety in TES and trades training facilities in British Columbia. The safety handbook focused on safe work practices and procedures that are required for a safe work and learning environments of TES, in which the risk of personal injury and disease is low.  This handbook was provided to teachers in TES as a guideline for safety skills and practices required in TES to keep students safe and to make them aware of the importance of safety in the workplace.  TES teachers in high schools are responsible for teaching their students both the basic and the advanced material required to learn safely and successfully without any adverse health effects or any workplace accidents.  Therefore, the first topics to be taught and explained to students in all TES include their safety.  Students in grades 8-10 learn how to work safely with tools, machines, and other equipment.  TES students are taught to understand and be aware of potential TES safety problems, as well as the appropriate precautionary measures when handling power tools and power sources (e.g., in metalwork TES:  welding equipment requires using eye protection and avoidance of fires), interpreting Workplace Hazards Materials Information Systems (WHMIS) symbols and handling materials related to such processes (e.g., solvents and chemicals), and when to respond to emergencies (e.g., fires, injuries, burns, cuts, etc.).  They also identify the place for safety equipment in the TES and the meaning of warning   9 signs.  Furthermore, TES teachers are responsible for teaching the students the basic and advanced technical work practices that include information about the operations and processes that take place in each TES and the purpose of each process (British Columbia Ministry of Education, 2002).   Beside all the above-mentioned, TES teachers have to assure that machines and tools in TES are only to be used by adequately trained students.  Unsafe practices and/or conditions in the TES and among the students during learning in TES, have to be prevented or eliminated, or corrected immediately.  TES teachers must therefore teach and enforce all the safety regulations.  Anytime an accident happens in TES, teachers have to complete a School Protection Program Incident Report. 1.2.3.3 Students’ responsibilities in TES TES students who take the safety and health course as a part of the HEADS UP! for Safety and TES curriculum, have to acknowledge, follow and practice the required procedures of health and safety that could affect their work.  They have to know how to use all personal protective equipment such as respirators, dust masks, earmuffs, gloves, face shields, welding helmets properly, and know the proper place and method of storage of all such equipment.  They need to work with their classmates as teams encouraging each other to work safely.  Any time an accident occurs or they find themselves working in unsafe conditions, they have to report that to the teacher immediately.  Students are also afforded the opportunity to act towards improving the safety conditions in their TES (British Columbia Ministry of Education, 2002).    10 1.2.4 Schedule and nature of teaching and working in TES  In high schools in British Columbia, TES teachers work for 6 hours a day and about 30 hours a week. The teacher may teach 1 to 4 TES classes a day and 4 to 15 TES classes a week. On average, a TES class lasts for 50 to 85 minutes. In some TES, there are two teachers (a teacher and an assistant or student-teacher).   The number of students in each TES class ranges from 20 to 30. They spend about 3 to 10 hours per week in TES depending upon their grade, projects and program schedule from one school to another.   At the beginning of each TES class, typically the teacher starts with an introduction of the day’s subject to the students, for 10 minutes. After that, the teacher uses tools and/or particular machines to give a brief demonstration.  For the rest of the class, the teacher supervises and monitors students as they perform technical projects and activities. Students in grades 8 to 10 take general TES learning and training of different interests of trades (covering the requirements for work safety) to select one or sometimes two different TES types related to his/her career interest in grade 11-12.   Students from grades 8 to 11 could be distributed in groups based on the projects they work on, and they work under the supervision of the TES teachers. However, students in grades 11 and 12 sometimes work individually on their own projects, as they can follow the workplace procedures and apply the process without full supervision from the teacher. They are considered advanced/independent learners at this level, with experience from the previous classes.    11 In addition, the teacher sometimes does work using machines or tools at the same time as the class. On average, about 45-60% of the TES machines could be used in each TES class by a varying number of the students.   1.2.5 Description of specific types of TES and related tasks  This section presents a description of the three most common TES in high schools in British Columbia (woodworking, metalworking and automotive). These three types of TES are of concern with regards to exposures, as discussed below in section 1.3. The description includes types and names of equipment, raw materials, control systems, and examples of products made in each type of TES. (Appendix A).  1.2.5.1 Woodworking TES In these TES, teachers train high-school students how to deal with different types of hand tools and other equipment to manufacture a variety of wood products, considering the requirements for personal safety in the first place.  A) Equipment and tools: Woodwork TES in high schools usually contain a number of power machines (e.g. planers, drill presses, radial arm saws, band saws, mortises, spindle sanders, etc.), portable power equipment (e.g. hand drills, spray guns, circular saws, orbital sanders, etc.) and hand tools (e.g. hammers, sanders, scrapers, screwdrivers, etc.) (Figure 1.1).    12 B) Raw materials: Different types of wood are provided, such as hardwood and softwood species. Species of hardwood available in woodworking TES include mahogany, beech, and oak. Species of softwood are pine, red wood, and red cedar. C) Control systems and personal protection equipment: Use of the aforementioned tools and wood species is associated with potentially hazardous noise and wood dust exposures. Therefore, a number of essential control systems are provided in these TES. Ventilation and local exhaust systems are installed in a number of these shops as a part of indoor environmental quality control of air and wood dust. In many cases, these two systems could be a permanent source of undesirable background noise. Noise control measures such as sound absorption materials are installed in a few of these TES.  Personal protection equipment (PPE) (e.g. dust masks, goggles, gloves, and hearing protection devices) are provided in these woodwork shops.               Figure 1.1: A large woodwork TES in Burnaby in BC.   13   D) Type of products: Working in a woodworking TES is not only about students learning how to use machinery and tools, but also about learning how to design/ plan their projects. They do this manually on paper with pencils, or using special graphics software, where TES students are not involved in any wood dust generating tasks.  Production in woodwork TES ranges from small wooden toys to a large piece of furniture (e.g. dining table and chairs, wardrobes) or recreational pieces (e.g., kayak boats).    1.2.5.2 Metalworking TES Each metal shop in high schools is designed functionally for metalwork and fabrication (Figure 1.2).  A) Equipment and process: The metalwork processes include: cutting (shearing the metal by band saws), forming metal (wheeling machines), machining and drilling (metal lathes, mills, press drills) and welding (e.g., arc welding). Teachers provide on-going education and training to students in safety procedures, metalworking process, arc welding and different machine operations. Arc welding is one of the topics of training in metalwork TES. They learn to work on two common types of arc welding that are Gas Metal Arc Welding (GMAW/wire feed) and Shielded Metal Arc Welding (SMAW/stick). The welding process is often separated from the general industrial zone by special curtains or some constructional walls (Figure 1.3). They also use different hand tools such as hammers, wrenches, screw drivers, taps and hacksaws.    14 B) Raw materials: Most of the metalwork TES use raw materials, such as plate metal, tube stock, square stock, formed and expanded metal, welding wire, and fittings.  Types of metal used include steel, nickel, copper, brass, aluminum and thinner metal sheet. C) Control systems and personal protection equipment: Ventilation systems are installed, and in operation, to maintain clear air in the TES. Some metalwork TES have local dust collectors installed to extract the metal dust that is generated while drilling or sawing. Sound absorption materials are installed on the walls of few of these TES to attenuate the noise.  In addition, a local extractor is often used to extract welding fume generated when students or teachers do welding in welding zones. In some cases, they might do welding in the general open area of the TES, without isolation. They use different types of metals as required for different projects.  Personal protection equipment (PPE) (e.g. goggles, gloves, welding helmets and hearing protection devices) are provided in metalworking TES.  D) Type of products: Production in metalwork TES includes small metal toys, copper medals, pictures frames, donation boxes, and different metal artwork for gates and door decoration and more.      15                     Figure 1.2: Metalwork TES in Surrey in BC. Figure 1.3: Welding zone in a metalwork TES in Richmond in BC.   16 1.2.5.3 Automotive TES Generally, automotive shops in high schools involve different types of operations and equipment to make them fully functional for teaching and practicing car maintenance (Figure 1.4).   A) Equipment and processes: Instructors in automotive shops demonstrate to students how car engines work, to perform car maintenance on the body and chassis, and the electrical and electronic systems. Students learn how to fix and balance car engines, change oil, replace expired valves, wire electrical parts, do exhaust welding, change brakes, and fix tires.  This requires students to use a variety of hand tools and equipment such as wrenches, pliers, hammers, and screwdrivers, lifting tools, tire tools and grinders. Some of these tools are associated with noise.   Welding is one of the processes that students can learn and perform as a part of the training in automotive shops.            Figure 1.4: Automotive TES in Richmond in British Columbia.   17 B) Control systems and personal protection equipment: Students and teachers in these TES are at risk to be exposed to noise, solvents, oils, welding fume and brakes asbestos. All automotive shops are supplied with ventilation systems. In the welding zones, there are fume extractors to collect fumes generated during welding.  None of the automotive TES examined in this study had noise control measures. Personal protection equipment (PPE) (e.g. goggles, gloves, welding helmets and hearing protection devices) are provided.    1.3  The shape of the problem  This section discusses problems and conflicts associated with the design and the use of TES from industrial hygiene and educational points of view.   1.3.1 TES teaching and working: Acoustical conflict Due to the diversity in TES design and settings in shapes, sizes and construction materials (reflective surfaces, low/high ceilings, acoustic tiles, etc.), and due to the two different usages of TES—they are used as classrooms for teaching and as industrial workrooms for working and making things—we hypothesized that acoustical conflicts would exist between the required environmental conditions and the existing regulations for industrial workshops and classrooms. In other words, the acoustical features of industrial workshops are different from classrooms, and this mainly relates to special designs and settings for each type of room. Each use or type of room has its own criteria for a number of related acoustical characteristics, including background noise, reverberation time (time required in seconds for a sound in a room to decay   18 60 decibels after the sound source stops), speech intelligibility index (a measure of to what extent speech from a talker is heard), and the reduction of sound energy with doubling of distance from the source (ANSI, 2009; Ondet and Sueur, 1995).   This acoustical conflict would exist, for instance, if the acoustical conditions in the TES, typical of an industrial room, failed to provide the acceptable acoustical conditions for a classroom. TES that have reflective or untreated walls with high ceilings and large volumes result in high background noise and high reverberation times that, consequently, adversely interfere with the speech quality needed for teaching by means of excellent verbal communication.   Indeed, the acoustical conditions in these environments play a dominant role in their quality. It is very important to emphasize that poor acoustical quality in a TES can adversely affect productivity and verbal communication for teaching and learning on teachers and students. It also adversely affects health, due to the exposure to high levels of noise, which cause hearing loss and voice loss. It causes distraction, learning difficulties, fatigue and discomfort, and it interferes with safety factors when high noise levels can mask warning signals/alarm, and could result in serious accidents (Berger et al., 1986; Cunniff, 1977; Clark et al, 2006).    1.3.2 TES teachers and students’ exposure to hazards: TES health and work safe practices  In TES classes today, teachers are responsible for the education and the health and safety of up to 30 students at a time. Many TES teachers may not be trained in occupational health and   19 safety for industrial environments, and may not monitor for exposures to occupational hazards.  On the other hand, their students are teenagers (12-18 years old) – sometimes with special needs (supervised by Educational Assistants with little shop experience) – with little health and safety training. Although a child at age of 12 years can be a worker in British Columbia under some circumstances (Ministry of Labour, 2015), there are no special regulations or exposure standards developed especially for students or youth, taking into account all different characteristics of young workers. Young workers or TES students are more vulnerable to exposures and less experienced with safety and health procedures in the workplace. The majority of the accidents in the workplaces in British Columbia are among young workers (WorkSafeBC, 2015; CCOHS, 2015).   That is why, for this age of workers (e.g. 12-15 years old), full supervision by an adult worker is a mandatory in the province of British Columbia (Ministry of Labour, 2015). The provincial workers’ compensation system provides special information sheets, brochures and manuals for young workers and students about workplace hazards, risks, safety policies, and rights and responsibilities to work or refuse unsafe work (WorkSafeBC, 2015).  In TES, the primary focus is on the safety practices and technical skills, while the industrial hygiene part that is related to exposure to hazardous materials and their health effects does not seem to be capturing the point of full consideration in high schools TES. The “Heads Up! For Safety” does well in targeting the protection of hands, eyes, and ears (the skin portion) from the point of view of safety to avoid skin injuries and burns accidents in TES.  In fact, students and teachers in TES can be at risk of exposure to serious industrial hazards such as noise and airborne hazards (e.g., wood dust, welding fume, solvents). Exposure to these   20 hazards at unacceptable and even low levels (especially among vulnerable students) in an uncontrolled workplace can result in adverse health effects other than hearing problems, physical skin injuries and burns.  In addition, teacher and student exposure periods are very different from those of adult and young workers in general industrial workplaces. A TES teacher’s work schedule is different from the regular adult work period (8 hr/day-40hr/week); TES teachers in British Columbia work in the classroom for 6 hours a day and about 30 hours a week. They could spend the majority of their classroom time in TES or they could split their time with other classes and school activities, with variable levels of exposure to industrial hazards. Students in the TES class work for an average of 1 - 3 hours a day in 1-2 different TES and 3 to about 10 hours during a school week.    Furthermore, students’ (12-18 years old) personal characteristics (biological and physiological) make them more vulnerable to exposures than adults. These adolescent students have higher rates of metabolism than adults and they consume more oxygen relative to their size than adults. Therefore, their exposure to airborne hazards is greater than it is among adults (Bearer, 1995).    Indeed, all factors related to TES type, characteristics, occupants’ categories, and work settings, make TES unique working and teaching places. TES teachers and students in schools are not always subject to the same scrutiny with respect to health and exposure to TES hazards, compliance with regulations, or application of policies. As a result, a gap was assumed to exist between the exposure to industrial hazards and the application of the control procedures and exposure regulations among TES teachers and their students. Therefore, there was a need to   21 explore and understand the exposure to the potential occupational hazards in TES for both TES teachers and students.    1.4  Potential exposures of interest  This section discusses from an occupational hygiene point of view the reasons why we selected three specific occupational exposures (noise, wood dust and welding fume) that TES teachers and students are exposed to in the three common types of TES (woodworking, metalworking and automotive). The exposures of interest were also based on pre-visits and walkthroughs of TES, information gathering, scientific literature, and observations from a significant number of the TES in three school districts in the Greater Vancouver Regional District in British Columbia. This also included discussions with health and safety representatives in each of the school districts in the study.  1.4.1 Noise  Teachers and students are exposed to noise in all of the three types of TES (woodworking, metalworking and automotive TES), in classes and during other school activities. In regular occupied classrooms, teachers were found in previous studies to be exposed to high levels of noise, due to the presence of the students, class activities and the excessive background noise from ventilation systems and other sources (Hodgson, 2004; Dockrell and Shield, 2006).   However, in TES, noise exposure could be worse, because teachers and students are exposed to very high “industrial” noise levels from the machines and tools they work on (e.g. arm saws, planers, hammers, orbital sanders, grinders, and lathe machines), and background   22 noise from known and unknown sources such as ventilation systems, dust collectors, activities from adjacent rooms, hallways, and outside traffic. In other words, teachers and students are exposed to noise from multiple sources, which makes the noise levels higher than if it was only from one source during their day at school. Moreover, TES with poor acoustics and poor room design could suffer from higher noise levels than properly treated ones.  Noise is defined as any unwanted or undesirable sound. It is not a new hazard; however, now it is one of the most pervasive occupational hazards.  Noise induced hearing loss (NIHL) is one of the most common occupational noise health problems (Berger et al., 1986). During a noisy day in workplaces, including schools and TES, workers’/occupants’ ears become fatigued. They experience a temporary reduction in hearing sensitivity or temporary threshold shifts (TTS); this hearing loss often recovers by the next day if there is no further exposure to high levels of noise after the work shift. However, it is shown in empirical studies that there is no clear difference in susceptibility to TTS “in particular” between teenagers and adults (Dockrell and Shield, 2006). However, with prolonged exposure to high noise levels NIHL occurs, which is also the permanent threshold shift (PTS) hearing loss. PTS happens when some or all of the hair cells in the organ of Corti in the inner ear are damaged permanently due to exposure to intense noise levels (Cunniff, 1977).  It is considered the most prevalent irreversible industrial disease (Borchgrevink, 2003; Brink et al., 2002; Smith et al., 1996).   NIHL is not the only adverse effect of noise; there are some non-auditory effects due to exposure to noise. First of these effects includes communication interference. Noise in industrial workrooms, including TES, is considered a major communication problem when it   23 masks and covers speech or warning signals that are required to do the job or to ensure worker safety.   Occupational noise can interfere with tasks, affect work performance and reduce the accuracy of work more than reducing the total quantity of work. Workers who do multiple tasks in one place and are exposed to high noise (such as TES teachers) are more likely to be adversely affected and distracted than if they are doing one simple task (Cunniff, 1977).   Industrial noise that interferes with speech determines the kind and amount of communication that can take place. It was learned from experience and experiments that at 80 dB occupants have to raise their voice and talk loudly, at 85 to 90 dB they must shout, and above 95 dB they must be close to each other to communicate (Berger et al., 1986).  High speech interference is experienced by most of the tech-workers involved in a number of tasks, including when using noisy tools (Singh et al., 2010).  In TES, background noise levels from ventilation systems and dust collectors “only” could reach up to 80-85 dB, and that provokes TES teachers to talk very loudly or shouts to be heard by their students during demonstrations; this would be worse when all machines are in operation. In some cases, teachers were found to be losing their voices due to repeating this performance for a longer time   In addition, noise is known as one of the physical stressors to which workers are exposed and that can affect so-called stress diseases. Stress effects of occupational noise are investigated by measuring a number of stress induced hormones (such as adrenaline excretion) from urine and blood samples before and after exposure to noise (Miki et al., 1998; Cavatorta et al., 1987). Noise at work increases and changes the levels of stress associated with hormones and stress indices (Cavatorta et al., 1987; Fruhstorfer et al., 1988; Tomei et al., 2003). The   24 common stress effects of noise include fatigue, insomnia, headaches, irritability, hypertension, cardiovascular disease, digestive disorders and ulcers and adverse changes in workers’ night-time sleep and heart rate (Miki et al., 1998; Gitanjali and Anath, 2003).  Actually, exposure to high levels of noise is not the only parameter/factor associated with non-auditory effects; other important acoustical parameters of the workplace environment include reverberation time and the reduction of sound energy with distance doubling from the source.   Noise exposure limits:  The recently adopted exposure limits from ACGIH (The American Conference of Governmental Industrial Hygienists) are the TLV-TWA (Threshold Limits Values- Time Weighted Average) for 8 hours per day and a 40 hour a workweek, and TLV-C (TLV –Ceiling) that is exposure limit that should not be exceeded even instantaneously.  Workers generally are exposed to noise in two different ways related to the type of task, sound intensity and time. These are continuous noise and impulse noise. Continuous noise from a source is stable over a certain period, such as power motor noise. Impulse noise is intense noise that is generated abruptly and randomly from hammering, stamping and pressing (Mäntysalo and Vuori, 1984).  TLVs of noise refer to sound pressure levels and durations of exposure that represent conditions under which ACGIH believes that nearly all workers (adults in most cases) can repeatedly exposed without adverse effects on their ability to hear and understand normal speech. They are based exclusively on available information from industrial experience, from experimental human and animal studies and a combination of the three (ACGIH,   25 2011).WorkSafeBC has recommended noise exposure limits in Part 7 of the Occupational Health and Safety Regulations (WorkSafeBC, 2005). This regulation recommends that a worker in any industry/workplace should not be exposed to noise above either of the following exposure limits: 1) 85 dBA for 8 hours/day 2) 140 dBC peak sound level  However, these limits were established to prevent a hearing loss at high frequencies (3000 and 4000 Hz) and they should be used as guides in the control of noise exposure. Moreover, for individual susceptibility, which includes young workers and students, these levels should not be considered as fine lines between safe and dangerous levels. The application of these limits of exposure to noise energy will not protect all workers from adverse effects on noise exposure. They will only protect the median of the population against a noise-induced hearing loss exceeding 2 dB after 40 years of occupational exposure for the average of 0.5, 1.2, and 3 kHz (ACGIH, 2011). It has been estimated that the excess risk of developing NIHL for 40 years of exposure to the 85 dBA recommended limit is 8% (NIOSH, 1998). Furthermore, hearing loss was found to be started from exposure to 75 dBA among youth/kids. Clinical evidences showed increased rates of hearing loss among teenagers in the last 3 decades. Their exposure to noise from some toys and musical instruments could be similar to occupational exposures in terms of noise levels. In fact, it has been recommended by EPA and WHO that in 24 hour – over a day individual exposure to noise should not exceed (Leq(24hr)) = 70 dBA. This exposure limit is the daily accumulated noise levels from occupational and non-occupational sources. This limit is the protective limit from noise induced hearing loss and non-auditory health effects. However,   26 some non-auditory effects can result from exposure to lower than 70 dBA, also based on the psychological pattern of the individual and that also include the age category (Neitzel et al., 2011; Cunniff,1977).  The action level: at anytime, if the workers are exposed to sound level ≥ 82 dBA and are likely to be exposed to such levels for a period which would be dangerous for hearing, the employer must appoint a professional to measure the noise levels and submit a report about the noise exposure and whether it is likely to exceed the 82 dBA. Requested action from the employer is to establish control procedures and protect the workers, inform the affected workers about the results and the risk of hearing loss due to the exposure to this level of noise (WorkSafeBC, 2005). This level could be used in some cases of noise exposure evaluation to assure the action limit is not or should not be exceeded.  However, for exposure durations that are different from 8 hours/day, then noise level of worker can be exposed to will be different from Leq = 85 dBA. Therefore, special correction calculations are applied to the noise level for measured/work periods different from 8 hours. According to the measurement condition and work period/pattern in TES, the following formula was applied for the correction to Time = 6 hours period of exposure daily for the teachers; [Leq = 10log10(Time,hr/8) + 85 dBA] (WorkSafeBC, 2007). This equation assumes there is no further noise exposure at or above 85 dBA for the other 18 hours of the day. From this equation, the Leq for 6 hours duration of exposure is 86.2 dBA, and for 1 hour period Leq is 94 dBA, which are based on a 3 dB exchange rate of noise exposures. These regulated noise exposure levels are related to the risk of hearing loss, but not individually related to other important non-auditory effects such as annoyance, comfort and verbal communication quality.  In practice, these TLVs   27 should be used by industrial hygienists to make decisions regarding safe levels of exposure to hazards in the workplaces. They were not established as standards to be used without full compliance with applicable regulatory procedures that include the analysis of the other health factors to make the adequate risk management decision (ACGIH, 2011).   Furthermore, if the workers in the workplace are exposed to noise higher than the exposure limits, it is the employer responsibility to provide and apply noise control measures and hearing conservation program. This program consists of noise measurements, education and training, engineered noise control, hearing protection, posting of noise hazard areas, hearing tests, and annual program review.  Hearing tests should be provided by the employer to the workers exposed to noise that exceeds noise exposure limits. There are two types of hearing tests that should be provided to the workers: A) initial hearing test that takes place after employment starts, but not later than six months from the date of employment; and B) a routine hearing tests that should take place every twelve months at least from the date of the initial test. These tests should be administrated by a hearing tester authorized by the board and the employer must assure that the hearing tester records and sends the results to the Board. The employer has to keep records of the annual hearing tests for each worker, the records of education and training provided to workers, and the results of the noise exposure measurements (WorkSafeBC, 2005). These tests were recommended for provision on adult workers as stated in the regulations, while there is nothing specified about whether or not there are recommended procedures to be considered when they are applied on young workers or students in vocational/technical shops. Although Vancouver Coastal Health provide a hearing screening service (initial hearing   28 tests) for students in their first year in high schools, it could be still required to provide annual or at least second hearing tests for TES students.  1.4.2 Wood dust Teachers and students are exposed to wood dust during woodworking tasks inside TES in high schools.   Wood dust is a light brown or tan, fibrous, powder-like substance generated when any wood piece of hardwood or softwood is processed –chipped, sawed, turned, drilled, sanded or polished (IARC, 1995).  Its natural chemical composition mainly contains cellulose, polyoses, and lignin.  In some cases, wood dust particles could contain a number of chemicals ‘added to wood in treatment’, such as herbicides, pesticides, or other preservation chemicals, including copper naphthanate, and pentachlorophenol used in the processing of some woods. It also contains some biological contaminants such as the molds and fungi grown on the bark of trees. These components in the wood dust represent a source of many allergic and sensitization effects on the workers (IARC, 1995; OROSHA, 2008). Actually, all wood dust is designated as class 1 carcinogen by the International Agency of Research in Cancer (IARC).   A teacher/student who is involved in woodwork tasks could inhale particles that are suspended in the air zone of the TES. The concentration of wood dust generated is related to the type of wood, tool used, task period, personal protection equipment used and dust extractor condition. When wood dust is inhaled, it is deposited in the nose, throat and airways. The amount of wood dust deposited in the airways depends mostly on the size of the dust particles (IARC, 1981; IARC, 1995). Wood dust size is influenced by the type of process; for   29 instance, sanding and grinding processes result in more cells shattering and produce smaller particles sizes than sawing or any rough woodwork process that results in chipping of cells (ACGIH, 2013). Each group/type of wood has its specific health effects; and this is the major source of the problem of exposure to wood dust (Milham, 1974; Bean et al., 2006).  In woodwork TES, teachers and students often use different types and species of wood in their projects; these include allergenic wood species, non-allergenic hardwood, and non-allergenic softwood (Table 1.2). Red cedar and black walnut are available in woodwork TES in British Columbia but not used a lot and must be avoided as regulated by WorkSafeBC because they cause asthma.  When wood dust is generated and suspended in the air zone it becomes an airborne   Table 1.2: Wood types and examples of species available or used in TES (Bean et al., 2006). Wood type  Name of species  Hard wood Oak, mahogany, beech, walnut, birch, ash Soft wood  Pine, spruce, red wood, western red cedar Other allergenic species Alder, Alpine ash, palm, maple, cypress, cedar of Lebanon   Table 1.3: Example of wood species and related adverse health effects (HSE, 2012). Wood species Adverse health effects Alder Dermatitis, rhinitis, bronchial effects Ash, Maple Decrease in lung function Beech Dermatitis, eye irritation, decrease in lung function Birch Dermatitis Western red cedar Asthma, dermatitis, mucous membrane irritation Mahogany Dermatitis, mucous membrane irritation, respiratory disorders Oak Asthma, sneezing, eye irritation  Spruce Respiratory disorders Walnut Sneezing, dermatitis, rhinitis   30 hazard. Table 1.3 shows examples of the common types that are used (e.g. in TES) and their relative health effects.  The problem is that some woodwork teachers may not have sufficient hygiene knowledge about these risks, which could result in exposures for students as well.    Exposure to wood dust at high or low concentrations is associated with different acute and chronic health effects that could happen to the lungs and the skin through inhalation, and/or skin and eye contact (Table 1.4).  It is shown that common health effects of wood dust vary from short-term skin and eye irritation to serious chronic damage, to the respiratory system and cancer (Demers et al., 1995, HSE, 2012, NIOSH, 2011). It is well known that wood dust is a human carcinogen, based on sufficient evidence of carcinogenicity from many studies in humans (Milham, 1974; IARC, 1995; Demers et al., 1995; NIOSH, 2015; NTP, 2000). Several studies showed that the risk of cancer (e.g. adenocarcinoma) is increased with the duration of level of exposure to wood dust (Demers et al., 1995).    Table 1.4: Wood dust associated acute and chronic health effects (Milham, 1974; IARC, 1995; Demers et al., 1995; Andersen et al., 1977; HSE, 2012; NTP, 2000; NIOSH, 2011). Exposure route Acute health effects Chronic health effects Skin or eye contact Eye irritation Chronic dermatitis (hands, forearms, eyelids, face, neck, and genitals) Skin sensitization (redness, scaling, and itching) Inhalation Respiratory irritation Respiratory sensitization – asthma Nasal dryness Nasal cancer – adenocarcinoma Sneezing and coughing Lung cancer  Hodgkin disease Nasopharynx and larynx cancer; DNA damage   31 Many TES teachers work and teach woodwork TES for years, and they probably were exposed to/inhaled a variety of wood dust types and concentrations; some of them may not use masks or respirators on a regular basis. In fact, based on personal observations and records in the TES included in the study, not all of the woodwork TES provided respirators and very few teachers or students were seen wearing disposable dust masks. It seems they were mostly relying on the control measures in the TES to eliminate the exposure to wood dust. However, they were observed wearing goggles and gloves to protect their eyes and hands from contact with wood dust and getting irritated.   In TES, wood dust particles are often generated from multiple sources at the same time. These particles suspend in the air zone and could transfer from one air zone to another. Exposure to this airborne wood dust also involves students who are not participating in any wood dust related tasks, and who are not protected.    Also it is important to mention that a cloud of wood dust is a potentially combustible dust; it will explode if a source of ignition is present (NIOSH, 2011; WorkSafeBC, 2015).   One of the major sources of this cloud of wood dust is the improper dust cleaning process in woodwork shops, especially when operators are non-skilled, which may be an issue when students are responsible for this process as part of classroom learning.   Some tools, such as orbital sanders, are associated with generating higher concentrations of wood.   Although there are control measures and protection equipment to eliminate the exposure to this toxic and combustible airborne hazard in woodwork shops, it is important to keep in mind that efficient operating of every control measure (e.g., local dust   32 collector, or local ventilation) is varied. This situation is made worse when personal protective equipment is not provided or not used.  Routes of exposure to wood dust:   Inhalation into the respiratory system and skin/eye contact are the two main routes of the occupational exposure to wood dust that target the human body, as briefly mentioned earlier (IARC, 1981; NIOSH, 2011).  In most cases of exposure to wood dust in woodwork shops, workers (including teachers and students in TES) seem to be aware of the eye and skin contact part as their safety major concern, and they do care about wearing eye protection goggles and hand protection gloves in addition to the blue apron. However, when it comes to inhalation protection and occupational health concern, they mostly rely on dust collectors, and often skip wearing dust masks or respirators available in TES. Sometimes this is thought to be adequate, but only if the dust collector systems are in excellent shape and working effectively to collect and extract all generated inhalable dust, at which zero particles can escape the hood of dust collectors and suspend and a cumulate in the air zone of the TES and then be inhaled by the worker.  These tiny particles are not visible when they are inhaled, and particles can enter all parts of the respiratory system (HSE, 2012). Size of inhaled wood dust particle determines in which regions of the respiratory system they would deposit; inhalable dust can be breathed into the nose or mouth, thoracic dust can penetrate the head airways and enter the airways of the lung, and respirable dust can penetrate beyond the end of the bronchioles into the gas-exchange region of the lung (ACGIH, 1999; ISO, 1995; CEN, 1993).  In this evaluation, inhalable dust size was selected for investigation as most appropriate for compliance and health.    33 Occupational exposure limits of wood dust: WorkSafeBC has provided occupational exposure limits (OEL) for inhalable wood dust based on the type of wood used.  The recently adopted exposure limits from ACGIH are the  TLV-TWA for 8 hours per day and a 40 hour a workweek for wood dust exposure.  They are based exclusively on health factors, and a conclusion drawn from a scientific review of the published and peer reviewed literature in industrial hygiene, toxicology, occupational medicine and epidemiology, which studied the exposure to wood dust and its associated health effects (ACGIH, 2011).   Wood dust exposure limit adopted by WorkSafeBC are as follows: A) Non-allergenic hardwood is 1 mg/m3; [A1* for oak and beach wood, A2* for birch mahogany, teak and walnut, 1: all designated as carcinogenic substances] B) Non-allergenic softwood: 2.5 mg/m3, notation: 1 C) All allergenic wood species: 1 mg/m3, notation: A1, A2, 1 There are no STEL (short term exposure limits: 15 minutes) or ceiling limits updated or adopted for very short exposure periods (WorkSafeBC, 2015). Wood dust exposure limits adopted by ACGIH are as follows: A) Western Red Cedar wood dust: 0.5 mg/m3, notation: 1 – DSEN; RSEN; A4 B) All other species: 1 mg/m3, notation: 1 C) Carcinogenicity: Oak and beach (A1); Birch, mahogany, walnut, and teak (A2); All other wood dust (A4) (ACGIH, 2016).  *[Notations: 1 = Carcinogenic to human, A1 = Confirmed human carcinogen, A2=Suspected human carcinogen]   34  ACGIH and WorkSafeBC state that during the period of exposure it is recommended that a worker’s exposure at any time does not exceed 50% of the TWA at which a worker can stay in compliance without the need of the exposure control plan (WorkSafeBC, 2015, 2003).   In fact, all wood dust has been classified as ALARA substance that exposure should be kept as low as reasonably achievable.  Therefore, it should be understood that the goal beyond these regulations is to reduce and eliminate the exposure to the possible lowest level below the exposure limit among adult and young workers. However, because of the difference in the individual sensitivity, and personal physiological and biological characteristics some individuals such as young workers might feel more discomfort and be at higher risk than adults at lower exposure concentrations than OEL (WorkSafeBC, 2011). Youth breathing rate is higher than adults; they inhale more pollutants per pound of body weight than adults do. This makes youth exposure to wood dust and airborne hazards riskier as they could inhale higher concentrations of wood dust than adults. Moreover, young worker and students are at greater risk to carcinogen exposures than adults as was reported by the Natural Resources Defense Council in studies on exposure to pesticides and its health effects on children/youth. Their distinctive diet and physiological immaturity make them susceptible to the toxic effects of pesticides (NRDC, 2016).  Therefore, the current exposure limits that are used for adult workers may be not protective limits for younger workers and students.    35 1.4.3 Welding fume In metalwork and automotive TES, teachers and students are exposed to welding fume during all arc-welding processes. This generated welding fume is a complex mixture of very small particles < 1 µm containing heavy metal vapors, which are formed when the electrical arc current melts and joins the filler rod electrode and the metal work-piece together. This welding fume is formed in the breathing zone of the welder and could be visible like a smoke, or not visible.  During unprotected exposure, welding fume heavy metals and gases could be inhaled into the respiratory system, could be ingested, and/or absorbed by the skin, and they can reach the bloodstream, in which welders could experience different acute and/or chronic health effects (Perkins, 2008; WHS, 2009).   Teachers and students might be at risk of inhaling heavy metals and vapors based on the type of arc welding and type of electrode/metal work-piece they are welding, as shown in Table 1.5 (Perkins, 2008).   Other factors for the risk of inhaling these heavy metals include the presence of a coating on the metal, the time and intensity of exposure, and ventilation (Ashby, 2002; AFSCME, 2011).  Table 1.6 shows that each welding fume component is a hazard in the short-term and/or the long-term of exposure varying from irritation of the nasal system and metal fume fever to serious damage to the kidney and the nervous system, and cancer of the lung and skin (OSHA, 2013; WHS, 2009).   Not all TES teachers are trained professional welders as is required in this trade, and they may not be familiar with the hazardous heavy metals they are exposed to, how they can enter the body, how they could affect their health. Again, a lack of occupational hygiene knowledge may in turn result in exposures (Perkins, 2008; WHS, 2009).     36  Table 1.5: Type of arc welding and metal and the related heavy metals and gases (WHS, 2009; OSHA, 2013; Perkins, 2008; Shane Ashby, 2002; Brown Jr, 2012). Welding type  Electrode/metal work-piece  Heavy metals and gases emitted as fume Shielded metal arc welding (SMAW) Stainless steel, nickel alloys, copper Chromium, nickel, copper Carbon – low alloy steel Iron oxides and total fume particles Gas metal arc welding (GMAW) Stainless steel and alloys Chromium, ozone Plasma arc cutting Carbon or low alloy metals Ozone, nitrous oxides, iron oxides Stainless and other steel Ozone, nitrous oxides, chromium, nickel, copper Different arc welding Copper, magnesium, aluminum alloys Beryllium, Aluminum  Stainless steel containing cadmium or plate material, zinc alloy Cadmium oxides  Coating and flux material for both low and high alloy steels Fluorides  Brass and bronze alloys, metal coated with lead based paint  Lead  Steel alloys, nickel alloys, iron stainless steel Vanadium, Molybdenum Galvanized and painted metal Zinc oxides Metal coated with rust inhibitors Phosphine Welding arc Nitrogen oxide Monel, brass and bronze alloys Copper High tensile steel Manganese  Coated metals by mercury Mercury   Occupational exposure limits of welding fume: WorkSafeBC has adopted ACGIH TLV-TWA, and provided occupational exposure limits (OEL) for most of the heavy metals and gases in welding fume. It is stated in Part 5.48.5 of the regulations of WorkSafeBC that the table of exposure limits for chemical and biological substances of exposure limits for chemical and biological substances should be consulted for the OEL for each substance involved in the fume a worker was exposed to during welding.    37 Table 1.6: Health effects of welding fume heavy metals and gases (OSHA, 2013; WHS, 2009; ACGIH, 2013). Hazard (Heavy metal, gas) Acute health effects Chronic health effects Nickel Irritation in nose, eyes, skin and respiratory tract Pneumoconiosis, lung cancer, males reproductive risks Copper Irritation of the eyes, nose, and throat; nausea metal fume fever  Vanadium Irritation of the eyes, skin and respiratory tract Bronchitis, retinitis, fluid in the lungs and pneumonia Lead Nausea, abdominal cramps, insomnia, lead poisoning Damage nervous system, kidney, digestive system, reproductive system and muscles  Chromium Skin irritation Lung cancer (Cr VI) Zinc oxides Metal fume fever  Fluorides Irritation to eyes, nose, and throat Joint and bone damage, fluid in lungs Nitrogen oxide Irritation to eyes, nose, and throat; abnormal fluid in the lung Lung problems such as emphysema Ozone Fluid in the lungs, headache Significant changes in lung function Manganese  Central nervous system problems Cadmium oxides Irritation of respiratory system, sore and dry throat, chest pain and breathing difficulty Kidney damage, emphysema and its suspected human carcinogen Aluminum   Irritation of respiratory system, pulmonary fibrosis Pneumoconiosis, bronchitis  Beryllium Metal fume fever, chemical pneumonia Sensitizer, damage to the respiratory tract, chronic cough, weight loss Arsenic Nerve inflammation, mortality due to cardiovascular failure Lung cancer, skin cancer, lymphatic system cancer  Iron oxide Irritation of the nose and lungs Pulmonary, edema, central nervous system, siderosis Mercury Stomach pain, diarrhea Tremors, emotional instability, hearing damage     38 It is important that the employer complies with the individual exposure limit for each component; when two or more components demonstrate similar toxicological effects it is recommended to apply additive exposure limit calculations in section 5.51 of the regulation (WorkSafeBC, 2003). The same situation applies regarding OSHA regulations for exposure to welding fume elements.  However, in this general evaluation of compliance among students and teachers, measurements are applied to the total mass of total dust, at which OEL for total welding fume is applied.  The justification for the welding fume TLV is based on studies of occupational exposure to welding fume, where air samples were taken inside the welder's helmet but outside the respirator. This way measures the concentrations of welding fume particulates that can reach the breathing zone of the welder and be inhaled if the respirator is not worn. OEL for welding fume as TLV-TWA is 5 mg/m3 for eight hours of exposure as adopted from ACGIH, which is believed that nearly all workers may be repeatedly exposed to it without adverse health effects. This TLV was only established to apply to fumes generated by the manual metal arc or oxyacetylene welding of iron, mild steel, or aluminum. ACGIH never intended this TLV to apply to welding operations involving toxic metals such as lead (ACGIH, 2011).   ACGIH and WorkSafeBC state that during the period of shift–e.g., eight hours– it is recommended that a worker's exposure not exceed 50% of the TWA at which the worker can stay in compliance without the need for the exposure control plan (WorkSafeBC, 2003). ACGIH has withdrawn the ceiling and the STEL values for total welding fume. Therefore, the action level (50% TWA = 2.5 mg/m3) would be used as the reference for exposure to total welding fume in short periods.   Indeed, the aim beyond these regulations and OEL is to reduce and   39 eliminate the exposure to the lowest level below the exposure limit. However, because of the difference in personal sensitivity, younger workers and students with higher rates of breathing and skin absorption, can inhale and absorb larger amounts of fume compounds than adults, and experience more discomfort at lower exposure concentrations than OEL. They might also suffer from higher positive response and health effects than adults (WorkSafeBC, 2003; National Research Council, 2015).    1.5 Existing knowledge  The following review summarizes the existing studies that have investigated the acoustical quality, and occupational exposure to noise, wood dust, and welding fumes, among teachers and students in TES or in similar small-scale workshops. The purpose of this literature review is to summarize what is known about the hazards, to identify gaps in the literature, and to provide a rationale for the studies conducted for this PhD dissertation. 1.5.1 Acoustical conditions in classrooms  Most acoustical studies were conducted in general classroom environments as opposed to technical-education environments.  The first part of this literature review will focus on the evidence of the acoustical conditions in classrooms, and the effects of poor classroom acoustics on outcomes among teachers and students.   40 1.5.1.1 Evaluation of acoustical conditions in classrooms and TES The evaluation of the acoustical condition in classrooms and their interference with the quality of communication and learning, and the need for high acoustical quality in classrooms, has been discussed in many scientific publications (Hodgson, 1994; Dockrell and Shield, 2006; Flexer, 2004; Klatte et al., 2010; Picard and Bradley, 2001; Shield and Dockrell, 2003; Picard and Bradley, 2001). The physical acoustical parameters typically evaluated in classrooms include background noise levels, reverberation times, speech levels/speech intelligibility index, and reduction of sound energy with distance doubling from a source (Houtgast et al., 1980; Steeneken and Houtgast, 1980; Warnock, 1980; Hodgson 1994; Ondet and Sueur, 1995; Hodgson et al., 1999; Knecht et al., 2002; Losso et al., 2004).  Background noise levels, a key measure in most acoustical studies, are typically measured using sound level meters, noise dosimeters, or special audio software. In unoccupied or empty classrooms, background noise is generated from ventilation or heating systems and other sources from adjacent rooms.  In previous studies, researchers reported high background noise levels ranging from 33 to 55 dBA, which in most cases exceeded the maximum allowable noise level of 35 dBA recommended by ANSI S.12.60 for unoccupied learning rooms or classrooms (Pekkarinen, and Viljancn, 1991; Celik and Karabiber; 2000; Boweden et al., 2002; Sato and Bradley, 2008; Shield and Dockrell, 2004).   In classrooms occupied with students and teachers, noise levels are even higher. An average noise level of 55 dBA was reported in occupied classrooms with students who were quiet, and 77 dBA when they were working or involved in activities (Dockrell and Shield, 2006). Consequently, teachers’ voice levels have been documented to rise to 80 dBA during these classes in order to be heard (Hodgson et al., 1999; Shield and Dockrell, 2003;   41 Picard and Bradley, 2001; Dockrell and Shield, 2006).  Not surprisingly, higher noise levels have been reported in TES when both machinery and ventilation systems are in operation, with background noise levels reaching higher than the permissible exposure limit of 85 dBA on average (Lankford and West, 1993). The second important parameter to be evaluated for classroom acoustics is reverberation time. Reverberation time (RT60) is the time needed, in seconds, for the average sound in a room to decrease by 60 decibels after a source stops generating sound (ANSI, 2009). There are several studies that investigated reverberation time in different unoccupied classrooms. The average of all results of those studies ranged from 0.2 s to 1.7 s (Iannace et al., 2002; Picard and Bradley 2001; Losso et al., 2004; Tachibana et al., 2002; Nishizawa et al., 2004), which are higher than the maximum allowable value of 0.6-0.7 s for unoccupied classrooms as recommended by ANSI S12.60 (ANSI, 2009) and for acceptable speech intelligibility.  Some authors have recommended background noise levels of 20 to 30 dBA and reverberation times of 0.4 to 0.5 as appropriate for optimal speech for students in classrooms and ultimately for optimal learning environments (Hodgson et al., 1999; Bistafa and Bradley, 2000).   1.5.1.2 Poor acoustical conditions and their effects on performance and health  It is stated that poor acoustical condition in classrooms can negatively affect teachers’ health and performance, which in turn can affect the quality of the learning environment for students.  Studies on teachers reported that high background noise levels and high reverberation times in classrooms cause high vocal effort, annoyance, speech interference and distraction (Crook and   42 Langdon, 1974; Åhlander et al., 2011; Pekkarinen et al., 1992; Pekkarinen & Viljanen, 1991). Teachers who work in these classrooms tend to raise their voices to more than 80 dBA to be heard by their students, with implications for subsequent serious voice problems when having to sustain this voice level over longer periods of time (Sala et al., 2001). Working in noisy environments that require the use of a loud voice to be heard over long periods is also associated with adverse psychological outcomes among teachers, including job-related stress and mental health conditions (Winkworth and Davis, 1997; Kristiansen et al., 2014). Job-related stress was found to be associated with voice problems among teachers (Russell et al., 1987; Messing, et al., 1997). Teachers represent more than 20% of voice-clinic load (Rammage et al., 2003). As a result, sickness absence, low job satisfaction and retention in the teaching profession are more common among teachers with voice problems or hearing difficulties in the classroom environment (Kristiansen et al., 2014).  In addition to the issues of noise, or the teaching or working environment, are issues associated with the learning environment for students.  Young students are more easily distracted by noise than adults, and thus they are not able to concentrate as well on their learning tasks (Klatte, 2010; Crandell, 1995).  Students also need to apply a greater amount of effort to primary learning tasks when noise is present in the classroom (Slater, 1968).  A number of studies indicate that high background noise levels in classrooms compromise students’ academic performance, reading and spelling skills, concentration, attention, behavior (Ando et al., 1975; Crook and Langdon, 1974) and speech perception (Klatte et al., 2010; Gumenyuk et al., 2004).    43 In summary, poor acoustical conditions of classrooms can negatively affect the quality of learning, and the health of teachers, through a number of different direct and indirect avenues, as summarized above. Failing to meet the required acoustic criteria in the design of many classrooms is surprising, as these environments are intended for the specific purpose of “teaching” and “learning”.  1.5.2 Noise in TES and small industrial shops  The following sections will focus on the evidence of noise exposures and related outcomes in small industrial workshops, and technical education shops specifically.  As there are limited studies on exposures in TES, studies on small industrial workshops that perform woodworking, metalworking and automotive activities provide evidence of analogous exposures and health outcomes given their similar machinery, tools and technical activities.  This section will summarize exposure levels and then the impacts of these levels on both the learning environment and on the health of workers and teachers (where applicable). 1.5.2.1 Noise exposures A few studies that have been conducted in TES that include woodwork, metalwork and automotive classrooms. Measured noise exposure levels were found to range from 85 to 115 dBA in woodwork TES. These studies concluded that acoustics conditions in vocational shops in schools were poor, and the major sources of noise in this shops are machines and tools. The importance of considering that young people have increased sensitivity to exposure noise, and the need to institute hearing conservation program in high schools were recommended in these studies (Pinder, 1974; Lankford and West, 1993; Koszarny and Jankowska, 1993).    44 Two previous studies in small automotive shops found that technicians have been exposed to excessive noise exposure levels greater than 85 dBA and 90 dBA during their work shift for 8 hours on average (Bejan et al., 2011; Jaylock and Levin, 1984), exceeding established occupational exposure limits. A study based on a self-reported exposure survey in small metalwork shops found that workers have been exposed to excessive noise levels (Rongo et al., 2004); some other investigations indicated that technicians in metalwork shops have been exposed to more than 95 dBA (Dalton et al., 2001; Mohammadi, 2008), which in all cases exceeds the permissible limit of noise exposure.   In a number of small woodwork shops, some researchers found that woodworkers have been exposed to noise levels of 90 dBA or higher (Dalton et al., 2001).    It is surprising that hazardous noise levels equivalent to industrial settings are present in technical education shops (TES), where educational settings should take into account how noise affects the health of students/teachers and well as the training/learning environments (see section above for impact on learning environments).  1.5.2.2 Health effects of noise exposures Exposure to occupational noise affects the work environment, including workers' health and efficiency (Noweir et al., 2012).  In fact, noise exposure is probably the most pervasive of all occupational hazards, and there is evidence for an association between noise and both auditory (e.g. hearing loss) and non-auditory (e.g. stress) health effects (Davies et al., 2009).     A few studies have investigated the relationship between the exposure to high noise levels in TES classes and noise induced hearing loss (NIHL) among students (Lankford and West,   45 1993). A study concluded that students in TES have poorer hearing conditions than those in regular classes (Pare and Filiatrault, 1987), and are more likely to experience high-frequency hearing loss (Woodford and O’Farrell, 1983). It was found that TTS (Temporary Threshold Shift) hearing loss has occurred among woodwork TES students after their exposure to high levels of noise during daily TES classes (Lankford and West, 1993). While TES teachers are at high risk of PTS (Permanent Threshold Shift) due to their longer exposures to high noise levels in woodworking and metalworking TES (Behar et al., 2004) this is also associated with not wearing hearing protectors (Lankford and West, 1993).  Exposure to high noise levels in small industrial workshops is associated with hearing loss among exposed workers (Dalton et al., 2001).  In small-scale industries, hearing loss was found to be greater among individuals and technicians involved in metalworking and woodworking than in some other industries (Evans and Ming, 1982; Dalton et al., 2001, Rongo et al., 2004). Indeed, individuals involved in woodworking and metalworking are more likely to have high-frequency hearing loss (Nondhal et al., 2006). Moreover, it has been found that occupational noise exposure is related to different indirect effects (Berger et al., 1991; Evans and Hygge, 2007). Stress, headache, annoyance and increased risk of accidents were reported to be associated with exposure to noise in small-scale industries (Rongo et al., 2004) including woodwork, metalwork and automotive shops.   While studies in classrooms and TES have investigated the link between noise and learning environment characteristics, there are no studies that have investigated indirect health effects in TES.  It is plausible that students and teachers exposed to the same high levels of noise exposure as observed in similar industrial workshops would be at risk of health effects,   46 although the effects may not be as severe or long-term for students with more short-term or intermittent exposures.  More research on exposure levels in TES is warranted.  1.5.3 Wood dust in small industrial woodwork shops and TES The following sections will briefly discuss the evidence of exposure to wood dust and its effects in small industrial and technical wood shops.  Due to the limited number of studies that investigated the occupational exposure to wood dust among teachers and students in woodwork TES, investigations that are done in similar small-scale woodwork shops can provide supportive evidence of analogous exposures and health effects. This section will summarize the exposure levels of wood dust and the impact on health and learning environment. 1.5.3.1 Exposure to wood dust  Several studies investigated occupational exposure to wood dust among workers in TES and small-scale woodwork shops and/or in specific woodwork processes/operations.  Few studies have investigated skin contact allergy among TES teachers due to exposure to wood dust.  Woodwork TES teachers were found to be exposed to 0.12 -1.18 mg/m3 of total dust.  (Ahman et al., 1995; Meding et al., 1996).   Studies in small-scale woodwork shops found that woodworkers have been exposed to high wood dust concentrations with geometric mean values that ranged from 2.9 - 9.9 mg/m3 (Brosseau et al., 2001; Rongo et al., 2004). Moreover, technicians who were involved in different woodworking tasks including sanding, carving, cutting, cleaning, and lathe or press operating, have been exposed to the highest inhalable wood dust concentrations, which ranged   47 from 4 to 25 mg/m3 (Teschke et al., 1999; Brosseu et al., 2001; Rongo et al., 2004). It was concluded that inadequate dust control at some wood working sites is associated with increased dust exposure levels (Jones and Smith, 1986).   Wood dust concentrations in woodwork TES seem to be close to those in small-scale woodwork industries.  1.5.3.2 Health effects of wood dust exposure Our literature search indicated a large number of studies evaluated the health effects associated with the exposure to wood dust in woodworking shops. However, there are only a few in small-scale woodworking shops and TES. The following summary represents these studies’ findings regarding the health effects of wood dust, to emphasize the evidence that students and teachers could be at risk of dangerous health effects.  Woodworking teachers in high-school shops, who were exposed to wood dust, had more severe nasal symptoms than those who were not exposed to wood dust, and these reported symptoms include runny nose, nasal irritation, and nasal obstruction (Ahman et al., 1996). Furthermore, woodwork teachers were also found to have symptoms of dermatitis, eyes irritations, throat dryness and skin irritations due to exposure to allergenic wood dust type in TES (Meding et al., 1996).  Deficiency in breathing and lung function was observed among young and old workers in small-scale woodwork shops, due to unsafe and long periods of exposure to wood dust (Meo,  2004). Moreover, exposed woodworkers could experience irritation in the eyes and in upper and lower respiratory airways, asthma, and non-asthmatic airflow obstruction (Vinzents and   48 Laursen, 1992), allergic respiratory diseases, dermatitis (Goldsmith and Shy, 1988), redness of the eyes, itching eyes, blocked and runny nasal passages of wood dust (Osman and Pala, 2009).  Indeed, it is indicated that wood dust health effects and symptoms among occupants of TES are similar to what workers in small woodwork industries could experience. However, there are few previous investigations in teachers and students in woodwork TES.  1.5.4 Welding fume in small industrial shops and TES Exposure to welding fume has been conducted in a number of worksites involved welding processes among a large number of welders and metal workers. This section summarizes the findings of studies measured exposure concentrations of welding fume in small-scale industrial shops and TES.   1.5.4.1 Exposure to welding fume   In metalworking and automotive TES, students and teachers’ exposures have not been evaluated yet, or not published. However, evidence from small-scale worksites that include welding processes showed significant occupational exposure to welding fumes, which draws a circle around the importance of investigating welding fume in TES. Researchers measured welders’ exposure to welding fume by collecting fume samples from the breathing zones under the welding masks. A previous study in a number of small metal workshops found that welders had been exposed to about 31.5 mg/m3 of welding fume as the total concentration of iron, chromium, manganese, lead and nickel (Jafari and Assari, 2004), that was exceeding the exposure limit. Furthermore, at another average-sized work-  49 sites, median mass concentrations for 3.5 hours exposure were 2.48 mg/m3 for inhalable particles of welding fume (Lehnert et al., 2012). Another study measured welders’ exposure working on manual arc welding to welding fume over 6-7 hours that is similar to teachers’ daily shift. It was found that welding fume concentrations over 6-7 hours ranged from 0.14 to 10.7 mg/m3 in the welder’s breathing zone (Stanislawska et al., 2010).  1.5.4.2 Health effects of welding fume exposure Studies on the health effects of welding fumes in TES could not be found. Previous studies mostly investigated health effects in general industrial sites; a few of them focused on small-scale worksites involving welding process.   Welders in small worksites who have been exposed to high concentrations of welding fume were found to experience bronchitis and respiratory symptoms including nasal allergies, cough, phlegm, wheezing, shortness of breath and asthma (Jafari and Assari, 2004). High levels of welding-fume exposure for 5.3 hours induced acute systemic inflammation among twenty-four young welders (Kim et al., 2005). Other studies concluded that exposure to welding is linked to airway irritations, bronchitis and pulmonary function changes, metal fume fever, chemical pneumonitis, chronic bronchitis, neurological impairment and a possible increase in the incidence of lung cancer (Antonini, 2003; Christensen et al., 2008; Erkinjuntti-Pekkanen et al., 1999; Lehnert et al., 2012). As the settings of small-scale worksites are similar to TES, teachers and students involved in the welding process would be at risk of experiencing the same health effects and   50 respiratory symptoms, although the exposure intensity and duration of exposure may differ between industrial and teaching environments.  1.5.5 Summary In summary, it is surprising that TES students and teachers may be exposed to noise levels, wood dust and welding fume similar to industrial environments, as TES should provide better and safer working and learning environments for students who are young and more vulnerable to exposures than adult workers/TES teachers. However, more information on their exposure levels in TES specifically is warranted, given limited studies.    Exposure to noise has implications for the acoustical and learning environment; exposure to wood dust, welding fumes and noise has implications for both student and teacher health.  Based on more detailed exposure and determinants of exposure data in TES using an occupational hygiene approach, it is possible to propose prevention, protection, design and control measures to improve the learning and working environments for both teachers and students. The combination of both learning and working environment makes a TES an interesting setting to measure exposures and to propose control and design measure. This is also related to what has been discussed in section 1.3, which considered two unique types of occupants, teachers and students with more special personal characteristics than other adult workers, for which some conflicts would exist regarding exposure time, exposure limits and governed regulations for which some endeavors to examine and investigate TES have to be considered.     51   1.6 Motivation for the study A number of relevant factors and stories motivated us to establish and conduct this project, also based on the materials discussed earlier in this chapter.  Acoustics problems and conflicts:  Before this research, we learned that a woodworking TES teacher in BC had lost his voice. This was the first motivation to consider conducting this study and to investigate the acoustical conditions of TES that were the reason for such serious injury. Furthermore, our preliminary search for documentation and evidence indicated that very little research has been done on exposures in TES.    The combined usages of TES (as classrooms and industrial shops) make them interesting settings to investigate. Each of the two uses of TES has its own acoustical criteria and regulations to be considered to achieve the effectiveness of learning technical (work) skills in an industrial setting. We assumed that failing to achieve any of these acoustical criteria for either use could result in acoustical conflict, which causes adverse effects on learning, and the health and safety of the teachers and students.   There is a gap in the existing knowledge about acoustical conflicts in learning environment and in small industrial workshops, which encouraged us to explore and examine the existence of this acoustical conflict in this interesting learning/working environment, taking into account the evaluation of all relative room acoustic parameters.     52 Occupational exposure to hazards between teachers and students:  Previous occupational health studies were only conducted in “similar” small-scale industrial shops, but few in TES. However, their findings suggest to us that teachers and students might be also at risk of hazardous exposures (noise, wood dust, and welding fume).  There are no special safety regulations developed for TES student and teacher exposures ensuring their full protection, which needed to be discussed in TES, necessitating further research and evidence.  TES teachers may not be trained in occupational health and safety in industrial environments, and their students may be inexperienced and more sensitive to occupational health and safety hazards associated with industrial processes such as welding, woodworking and automotive repair.    Additionally, our literature search indicated a gap in the existing knowledge in this area, which made it an interesting and a challenging issue to explore, to study the exposure of teachers and students to TES hazards and their control.   It is important to remember that TES were established to shape a future career for high school students.  At the same time, it is required that teachers teach/work and students learn/work effectively and safely, without any single detrimental effect on their health.  This encouraged us to find feasible solutions and better ideas to make TES safer and healthier environments that ensure minimum levels of exposure with minimum adverse effects on the quality of learning and working among the teachers and their students who are more vulnerable to exposure to TES hazards and their health effects.   53 To our knowledge, this is the first comprehensive study of occupational hazards in TES; it will fill gaps in the existing knowledge of teacher and student exposures to those hazards, and the determinants of exposure and possible interventions (controls, class procedures, policies) to reduce hazards. Fundamentally, this project provides insights into the conflicts that exist between using TES as an industrial workshop for work, and as a classroom for teachers to teach and students to learn, and the gaps/conflicts exist between teachers and students’ exposures and safety due to having industrial settings in educational environment.   1.7 Thesis objectives  This research project represents a full-exposure investigation among teachers and students to noise and airborne contaminants in high-school Technology Education Shops (TES), and their control. In order to accomplish this goal practically, three specific objectives were addressed as they represent the central structure of this thesis:  1- To investigate the acoustical conflict in TES environment due to the two uses of TES (as an industrial workshop and a classroom).  The acoustical characteristics of industrial workshops are different from classrooms. Therefore, experimental methods were used to measure these characteristics and assess compliance of each use in relation to applicable acoustical standards.  The acoustical parameters in TES that were studied included background noise levels, reverberation times, speech intelligibility, and DL2 (the decrease of sound level with distance doubling) in industrial rooms.    54 2- To evaluate the exposures of teachers and students to noise and airborne hazards (wood dust and welding fume) in TES. The results of each type of exposure were assessed for compliance with WorkSafeBC regulations. 3- To suggest suitable control measures to make TES healthier places for teachers and students to work and learn.    1.8 Overview of the thesis The plan for this study followed the industrial hygiene framework in workplaces, which consists of a number of principles and a series of steps, including information gathering, assessment and a recognition of the hazard, evaluation of the exposure, and finally the control measures (Perkins, 2008). First, information (e.g., processes types, raw materials, construction, settings and design, employee demographic, nature of work, types of hazards generated, and control measures available) of TES were gathered from the pre-visits, meeting and conversations with the TES teachers and schools’ safety representatives, and from the walk-through in a number of TES in Great Vancouver. Furthermore, this also included the search in literature and toxicological information about the recognition and assessment of the occupational hazards, the potential magnitude of their health effects, and the possible conflicts that arise between teaching and working in TES. The screening and assessment of all the gathered information contributed to the identification and recognition of the most imperative occupational hazards, processes and possible conflicts to evaluate.    55 The preceding information informed a strategy to evaluate occupational exposure to the most important hazards (noise, wood dust and welding fume) in TES, and to investigate the possible conflicts (e.g., acoustical conflict) that could exist due to the use of TES for teaching and working.  Planning to evaluate the exposure hazards included a participant recruitment strategy and a sampling strategy – to collect data on both teachers’ and students’ levels of exposure to each hazard in each type of the selected TES, during different processes at different points in time. The development of the exposure sampling strategy included consideration of: 1) the type of monitoring (personal or area); 2) the technique/instruments to be used for exposure monitoring; 3) whom to monitor; 4) the size of the participant sample and the number of samples; and 5) the time required for monitoring.   This step was followed by assessing all the collected data with respect to the relative regulations for the permissible exposure limits for each hazard, and guidelines for teaching environments. The outcomes of this evaluation phase provided valuable information about the exposure to hazards among the teachers and the students, the design of the workplace and the settings required for teaching and working, and the condition of the control measures in the investigated TES.   Finally, the interpretation of the evaluation results provided recommendations for prevention of exposure and enhancement of the quality of teaching and working in TES using the hierarchy of control measures in workplaces (Figure 1.5). In this stage it was important to suggest the control measures that can be applied in TES based on the principles of the hierarchy of controls and the conditions for teaching and learning environments in parallel. Hazards control in a workplace might be applied in a number of ways: 1) control at the source   56 that generates the hazard. This is the most effective control procedure that could eliminate the hazard generation (e.g., by substitution for the process or the raw materials associated with hazard generation, maintenance of the process/machine, and apply some engineering controls on the source); 2) control along the path to reduce the worker exposure to the hazards by engineering controls (e.g., install sound barrier between the sound source and the receiver, or install ventilation system) ; and 3) control at the worker by providing personal protection equipment (PPE), training in safety, or administrative procedures and disciplinary actions. These control measures at the worker are the least effective control procedure and should only be considered as the last resort if neither control at the source and the path are feasible (NIOSH, 2015; HSE, 2015).             According to what has been described above, the overall structure of this thesis consists of four major phases explored and discussed in seven chapters (Figure 1.6).  Figure 1.5: Hierarchy control measures (NIOSH, 2015; CCOHS, 2015; HSE,2015).   57 Phase 1 of this framework first involves the preliminary information gathering and data collection. The other part (Chapter 2) of phase 1 presents the methods used for site selection and participant recruitment. This part includes important data regarding the characteristics of the selected TES that are required for the subsequent evaluation phases. Two evaluation phases, including the evaluation of acoustical conditions and the evaluation of occupational exposure to noise, and airborne hazards, are presented in Chapters 3 and 4, respectively. Each chapter includes materials and methods, standards, results and discussion and summary.  Chapter 5 is overall discussion of the evaluation phase. The last phase of this framework presents control measures, which are discussed in Chapter 6.   Information in this chapter was based on the results found from the earlier chapters of information gathering, and the evaluation results.  Chapter 7 is the conclusion that includes a summary of the objectives achieved and the empirical findings, the scientific contribution of the dissertation, statements on the limitations and the strengths of the study, its research implications and recommendations for future work.     Figure 1.6: Thesis structure based on the industrial hygiene framework of evaluation and control of exposure to hazards.   58   2 Site Selection and Participant Recruitment  2.1 Site selection This research was conducted in the lower mainland of Vancouver in three school districts in the cities of Richmond, Burnaby and Surrey. It was mandatory to apply for ethical approvals from University of British Columbia and then from each school district individually; upon receiving the approvals, we were able to contact and visit a number of different schools (randomly selected) in each district. Furthermore, it was required for the researcher to seek approvals from each school. Schools and TES approvals to participate had to be obtained individually, and included school administration approval, and teacher and student agreements to participate in the study. In the end, 15 schools accepted to participate.   2.1.1 Pre-visits and walkthrough surveys in TES  After getting official approvals from the school districts in Burnaby, Richmond and Surrey, organized pre-visits took place at a number of random schools. A survey of site characteristics relevant to exposure variability and determinants was developed and administered. Part of this walkthrough survey was completed during the pre-visits. The data included the shops’ physical characteristics (type, age, construction layout, ventilation system), common or specific types of process in the workplace, the kinds of raw materials and products and the hazards of concern in each TES.  Indeed, this stage resulted in selecting three main types of TES: woodworking TES, metalworking TES and automotive TES.     59  Further detailed information for the investigation was collected for the selected TES during the actual measurement days. These data included room size, construction materials, equipment/tools/machines (type, number), information about the students taught (number of classes, number of students, grade), nature of work (teacher daily work hours, number of shifts, times, types of tasks and jobs), and the existing control measures (ventilation, local exhaust, personal protection equipment, noise control materials), and were filled in information sheet (Appendix B).   2.2 Participant selection and recruitment procedures 2.2.1 Obtaining permission for participation  Each high-school heath-and-safety district representative helped the researcher to contact a number of the selected school principals (if interested to participate), and required visiting the TES and meeting with the TES teacher/s.  At the meeting, the researcher presented and explained the research plan and procedures to the teacher/s. A teacher consent form had to be viewed and signed by each teacher interested in participating. Each participating teacher helped the researcher to choose a student from his/her class, inform him/her about the idea of the research, and send parent consent forms to be read and signed by each student’s parent. The purpose from these consent forms was to get individual participant’s permission to allow us to enter the TES, communicate with the participants and perform the required personal monitoring on them. (Appendix G)   60 2.2.2 Recruitment criteria Participants in this study included teachers who may be exposed to noise and wood dust or welding fume, students who took classes in the selected TES and were exposed to noise and/or wood dust and welding fume, and students with parental permission to be sampled in this research work.  Part-time teachers in the selected TES and students without parental permission were excluded from participation in this study.  Comprehensive area, teacher and student personal sampling of hazard exposures was performed in 15 secondary schools in 26 TES (9 unoccupied and 17 occupied/unoccupied) distributed in Richmond, Burnaby and Surrey school districts; these included the three selected types of TES (wood, metal and automotive) as shown in Table 2.1.    Table 2.1: Investigated TES types and numbers in each school district. School District TES # Total Wood Metal Auto Burnaby 2 1 1 4 Surrey 5 4 1 10 Richmond 6 4 2 12 TOTAL 13 9 4 26   Table 2.2 shows the characteristics and constructions of the 26 TES.  Figures 2.1 and 2.2 show examples of two of typical TES floor-plans (Appendix C).      61  Table 2.2: Characteristics and constructions of the twenty-six TES. # TES  Age TES Size Ceiling Construction materials Old/new Area, m2 Volume, m3 Height, m Floor Ceiling Walls 1.  *WB1 Old 312.5 1500 4.8 Concrete Steel (S) Concrete/Drywall 2.  WB2 New 200 1400 7 Concrete Steel  Concrete 3.  WR1 Old 210 966 4.6 Concrete Steel Concrete/Drywall 4.  WR2 New 104 478.4 4.6 Concrete Tiles (T) Concrete/Drywall 5.  WR3 Old 312 1497.6 4.8 Concrete Tiles Concrete 6.  WR4 *Old 253.5 1521 6 Concrete Concrete (C) Concrete 7.  WR5 Old 217 716.1 3.3 Concrete Concrete Concrete/Drywall 8.  WS1 *New 230 1610 7 Concrete Steel Concrete/Bricks 9.  WS2 Old 210 1470 7 Concrete Steel Concrete 10.  WS3 Old 200 1400 7 Concrete Steel Concrete/Bricks 11.  WS4 Old 232.75 837.9 3.6 Hardwood C/T/Foam Concrete/Drywall 12.  AR1 New 254.1 2032.8 8 Concrete Steel Concrete 13.  AR2 New 262.9 1235.63 4.7 Concrete Steel Concrete 14.  AB1 New 200 1400 7 Concrete Steel Concrete 15.  MS1 New 233 1631 7 Concrete Steel Concrete 16.  MS2 Old 240 1824 7.6 Concrete Steel Concrete 17.  MS3 Old 220 1540 7 Concrete Steel Concrete/Bricks 18.  MR1 Old 200 920 4.6 Concrete Steel Concrete 19.  MR2 Old 304.5 2040.15 6.7 Concrete Steel Concrete 20.  MR3 Old 108.04 356.532 3.3 Concrete Tiles Concrete/Bricks 21.  MR4 Old 168 840 5 Concrete Steel Concrete 22.  WR6 Old 198.7 914.02 4.6 Concrete Steel/Wood Concrete/Drywall 23.  WS5 Old 150 750 5 Concrete Steel Concrete/Bricks 24.  MS4 Old 110 440 4 Concrete Tiles Concrete/Bricks 25.  MB1 New 312.5 3281.25 10.5 Concrete Steel/Tiles Concrete/Bricks 26.  AS1 Old 188.4 1318.8 7 Concrete Steel Concrete/Bricks  A special coding was assigned to all TES, which identifies the type of TES (wood, metal, or auto) and its school district (Richmond, Burnaby, Surrey). For example: Wood TES in Burnaby = WB, Metal TES in Surrey = MS, and Automotive TES in Richmond = AR, etc. Old: > 10 years, New: < 10 years from the date of the study.   62                        Figure 2.1: Floor plan of woodwork TES in Burnaby. Figure 2.2: Floor plan of metalwork TES in Surrey.    63  3 Evaluation of the Acoustical Conditions in TES    3.1 Introduction This chapter represents the evaluation of the acoustical conditions in TES. It consists of six sections, including objective, definition and standards for the acoustical parameters, materials and methods, results, discussion and lastly the summary of the whole chapter. To perform this evaluation and investigate the acoustical conflict in TES, special surveys/measurements were performed for a number of relevant acoustical quantities in 26 TES.  The following sections describe the procedures taken to accomplish this investigation.    3.2 Objective The objective of this evaluation is to investigate acoustical quality and the possible acoustical conflict in TES used as both classrooms and industrial workshops. This was achieved by evaluating the design/settings of TES and all related acoustical characteristics of twenty-six high school TES in British Columbia when unoccupied, and in seventeen of them when occupied and in normal operation. The measured relevant acoustical parameters included background noise levels and equipment noise, reverberation times, speech intelligibility index and the reduction in sound energy per distance doubling from the source in TES.  An acoustical conflict would exist if the acoustical conditions in the TES, typical in an industrial room, fail to provide acceptable acoustical conditions for a classroom, if they are    64 typical for a classroom and not acceptable for an industrial room, or if TES acoustical conditions fail to meet the requirements for both classrooms and industrial rooms, taking into account the influence of the TES (design) characteristics on the criteria for both purposes..    3.3 Definition and Standards This section includes the definition and standards for the measured acoustical quantities for classrooms and industrial workshops.  3.3.1 Classroom acoustics  3.3.1.1 Background noise levels (BNL) Background noise is comprised of noise from building systems, exterior sound transmission, and sound transmission from adjacent spaces. It is measured in a certain space and time in the absence of any identified sound sources. In a classroom with occupants, excessive background noise can seriously degrade the ability to communicate, decrease concentration, and induce discomfort (ANSI, 2009). The maximum background noise levels in dBA for unoccupied learning rooms are presented in Table 3.1, based on room volume as suggested by ANSI standards.  3.3.1.2 Reverberation times (RT) In rooms, sound can continue to reflect for a period of time after a source has stopped producing sound. This prolongation of sound is called reverberation. Reverberation Time (RT60) is defined as the time in seconds required for the average sound level in a room to decrease by    65 60 decibels after a source stops generating sound. In practice, RT is affected by two major factors related to the room; these factors are the size of the room and the amount of absorptive and reflective surfaces. In general, and regarding room size, RT is much longer in large spaces such as TES than small spaces such as individual classrooms. Moreover, RT is shorter in rooms with effective absorptive surfaces than in rooms with reflective surfaces. The RT of a room can strongly affect the speech intelligibility; the earlier the arriving energy (short RT) the better the speech intelligibility. However, in big and untreated/reverberant rooms RT values may be longer than the acceptable time that could result in poor speech intelligibility (ANSI S12.60-2009). For acceptable classroom acoustical quality ANSI has recommended maximum reverberation times in seconds in unoccupied learning rooms according to the room volume as shown in Table 3.1.  Table 3.1: Maximum A-weighted steady background noise levels (BNL) and maximum reverberation times (RTs) in unoccupied, furnished learning spaces (ANSI S12.60-2009). Learning Space Max. BNL dBA Maximum RTs (s) – for sound pressure levels in octave bands with mid-band frequency 500 to 1000 Hz Core learning space with enclosed volume <283m3 35 0.6 Core learning space with enclosed volume >283m3 and < 566 m3 35 0.7 Core learning space with enclosed volume >566m3 and all ancillary learning spaces 40 Reverberation control for large core learning spaces C3.3 (ANSI S12.60-2009)      66 3.3.1.3 Speech intelligibility index (SII) SII is a calculated value ranging between 0.0 and 1.0, which is strongly correlated with the intelligibility of speech (ANSI, 1997). In other words, SII indicates to what extent speech is understood in a room when there is communication between a talker and listener/s at a certain distance. For example, if the calculated SII is 1.0 then the speech is clearly received and the message is understood. On the other hand, when the SII value is close to 0.0 then the conversation quality is poor and is not acceptable in rooms such as classrooms where learning requires understanding of what the teachers are saying. In fact, the SII is affected by three acoustical parameters: BNL, RT, and speech level (ANSI, 1997). It is calculated from these three parameters in frequency bands from 125 – 8000-Hz. The SII acceptability/design criteria for speech intelligibility in classrooms and industrial workshops used in this research are shown in Table 3.2, based on information in the reference EN-ISO 9921 (2003) for the assessment of speech communication.    Table 3.2: Proposed speech intelligibility index (SII) and speech-intelligibility (SI) quality criteria (EN-ISO9921 - 2003). SII range SII<0.3 0.3<SII<0.45 0.45<SII<0.6 0.6<SII<0.75 SII>0.75 SI quality ‘bad’ ‘poor’ ‘fair’ ‘good’ ‘excellent’      67 3.3.2 Industrial workroom acoustics  3.3.2.1 Reduction of sound level with distance doubling (DL2) The reduction of sound level with distance doubling (DL2) is one of the most important parameters that describe the acoustical performance in industrial rooms with respect to its acoustical characteristics, independent of its noise sources. Industrial rooms have a variety of sizes, shapes and designs. Moreover, fittings (the contents - e.g. furniture, machines, booths) are very diverse in industrial rooms. Therefore, the parameter DL2 represents the reduction of sound level per distance doubling of the spatial decay curve recorded in a clear area of the room with a single omnidirectional reference sound source in operation (Ondet and Sueur, 1994). The proposed acceptability/design criteria for DL2 in unoccupied, “fitted” industrial workshops by Ondet and Sueur are shown in Table 3.3. These criteria specify minimum values of DL2 as a function of the workshop floor area for which workshop is considered as ‘acoustically treated’, otherwise the workshop is considered ‘reverberant’ and containing insufficient acoustical treatment for noise control.   Table 3.3: Minimum DL2 (in dB/distance doubling) criteria for LA,tot in unoccupied, fitted-  industrial rooms as a function of floor area, S (Ondet & Sueur, 1994).      S (m2) DL2 criterion (dB/distance doubling) <210 3 210<S<1000 1.5log(S) – 0.5 >1000 4    68 It is important to consider that the above-described acceptability/design criteria involve the acoustical characteristics of the unoccupied and occupied TES.  It is the acoustical conditions in the occupied TES that eventually are of main interest, because they can affect teachers and students directly. However, the acoustical characteristics of the unoccupied TES deliver valuable information about the contributions of the TES environment and its noise sources to the occupied conditions, information that is supportive for noise control. 3.3.2.2 Reverberation times (RT) Reverberation time in unoccupied machine or industrial workshops is suggested to not exceed 1.0 s at middle frequencies (Warnock, 1980).  3.4 Materials and Methods The measurements of the following acoustical parameters were conducted by area sampling in the twenty-six TES in Richmond, Surrey and Burnaby. 3.4.1 Background noise levels (BNL) Background-noise levels (BNL) in octave bands were first measured once in all 26 TES under unoccupied conditions with the building ventilation system on, and all dust collectors and machine tools off. This was done using an integrated sound level meter (ISLM) with octave-band analyzer [Rion NA-29E] with slow response in each TES, at about 5-6 positions for 10 seconds of measurement (Figure 3.1).  BNL was also measured in seventeen occupied TES, which were in normal operation by teachers and students, with the ventilation and/or dust-collector systems on, and shop equipment operating. This was done to develop a clear    69 understanding of the factors that may influence high noise levels in these environments, and to help in suggesting the proper controls. Total, A-weighted BNL was calculated from the measured un-weighted BNLs. The average BNL in each TES was also calculated and compared with the standards for classroom/design criteria presented in Table 3.1. Moreover, to measure the noise levels generated from a number of individual machines and tools, each machine was operated and measured separately with other machines off, using same integrating sound level meter (ISLM) with octave-band analyzer [Rion NA-29E], over the whole period of each related task.   3.4.2 Reverberation times (RT) The calculation of RTs (Early Decay Time, EDT, most relevant to verbal communication) was done from impulse responses measured using the WinMLS software, using an ‘omnidirectional’ (dodecahedral) loudspeaker array as the sound source. This loudspeaker was placed at the centers and in the corners of the unoccupied TES with all shop equipment, machines and building services turned off. The sound level meter [Rion NA-29E] was used as the receiver, and was located at positions in the TES not close to the source, walls, or any obstacles (Figure 3.1).  In each unoccupied TES, the room-average RT was calculated and compared with classroom acceptability/design criteria (see Table 3.1), and with the Warnock reverberation-time criterion (Section 3.1.2.1). Note that Warnock did not stipulate whether or how the workshop RT criterion varies with frequency, so it was assumed here that it applies to all octave bands, with the values at 500 and 1000 Hz being of particular importance since they relate to verbal communication quality.    70  3.4.3 Speech intelligibility index (SII) SII was calculated from measured octave-band speech level (SL), BNL, and RT values, according to methods described in ANSI S3.5-1997 (1997). SII values were calculated for a ‘teacher’ speaking at four assumed vocal outputs (‘normal’, ‘raised’, ‘loud’, and ‘shout’). 3.4.3.1 Speech levels (SL) To obtain speech levels for each TES, octave-band sound-pressure levels were measured in the TES using a speech source (a mannequin loudspeaker that simulated a human talker) radiating broadband noise, which was calibrated for its sound-power output. An audio amplifier was connected to the speech source and to a laptop to generate and control the broadband noise. The speech source was placed at typical teaching positions in each TES where the teacher stands in front of the students to speak and demonstrate. The calibrated ISLM [Rion NA-29E] was located at three different typical ‘student’ listening positions near to and farther from the speech source over a range of distances of 1 - 4 m. The heights of both the noise source and the receiver were at the average of a teacher’s and a student’s height, which is about 1.5 m (Figure 3.1).  3.4.3.2 SII calculations SII calculations for each TES were done using the SII prediction spread-sheet created by Dr. Murray Hodgson at UBC. This spread-sheet is based on the American National Standards (ANSI S3.5-1997) method, which evaluates SII for an assumed talker voice level, from octave-band    71 speech levels, background-noise levels and reverberation times. SII values were then calculated at the SL measurement distances from a source (1, 2, 4 m).  Measured octave-band levels were corrected to realistic SLs using the differences between the speech-source sound powers and those of average adult talkers speaking with each of the four vocal outputs (normal, raised, loud, shout), determined from data in ANSI S3.5-1997. Measured levels were also adjusted for background noise, if necessary. SII results were compared with the acceptability/design criteria in Table 3.2.  A passing grade was assigned if ‘good’ or better speech intelligibility (SII ≥ 0.6) was obtained with no louder than a ‘raised’ vocal output.   3.4.4 Reduction of sound level with distance doubling (DL2) Measurements of DL2 were made generally following ISO/DIS14257-1999. An omnidirectional (dodecahedral-array) loudspeaker was placed at positions corresponding to distance doublings (i.e., 1, 2, 4, 8, 16 m, etc.) from a receiver (the RION sound level meter) along one unobstructed line across the TES, taking into account its length to assign feasible measurement distances. The heights of the noise source and the receiver were 1.5 m. At each position a calibrated Rion NA-29E sound-level meter measured the octave-band sound-pressure levels (Figures 3.1 and 3.2). These levels were plotted as a function of distance, the best-fit logarithmic-regression curve and its equation were found, and the slope DL2 in dB/distance doubling was determined; if the equation of the best-fit line is Lp(r) = A – B log (r), then DL2 = -B log (2). Results were compared with the acceptability/design criteria in Table 3.3.    72 3.4.5 Data and results analysis  Collected data from each acoustical measurement were checked, cleaned from errors and prepared for the required further calculations. Results for each acoustical parameter were logged, coded and ordered in separate spreadsheets in excel to build up the database structure.  Database structure also included all TES relevant information and characteristics (age, room volume, school district, TES type, acoustical controls available, etc.).  Results of each parameter were categorized based on a number of selected determinants (TES type, room volume, acoustical control measure available, TES age).  Final results of each acoustical variable for all TES were tested for compliance with criteria for industrial workshops and with criteria for classrooms. This method was also conducted to examine for possible acoustical conflict in TES. Furthermore, statistical analysis was performed on the categorized results as the following: A) Descriptive statistical calculations to assess the distribution of the acoustical measurements:  Averages/means  Minimum and maximum   Standard Deviation  Minimum – Maximum  Range B) Preliminary factors affecting the acoustical characteristics were analyzed by correlation (r) calculations to determine relationship between the variation in acoustical characteristics (BNL, RT) and TES characteristics (e.g. room volume, ceiling height, TES age in years, current acoustical treatment +/-).  Finally, results were plotted in graphs for illustrations.    73  Figure 3.1: A floor plan of a woodwork TES. Also shown the positions at which loud speakers, sound level meter, and speech source were located for the acoustical measurements.               16 m   Figure 3.2: Measuring DL2  in unoccupied metalwork TES. Figure shows Sound level meter (in yellow circle), and an Omni loudspeaker (in red circle). The distance was 8 meter between each of them.    74  3.5 Results The acoustical quality of 26 TES as classrooms and industrial shops, was evaluated by measuring the related acoustical characteristics investigating the acoustical quality and conflict in TES and how this is associated with TES design and settings. This section presents the characteristics of TES design and the acoustical parameter in each of the 26 TES.   3.5.1 TES design and settings  Our literature review and primary search didn’t locate governing standards or regulations for high-school buildings, classrooms and TES in British Columbia. We were not able to identify any typical/standardized designs for TES in high schools, especially regarding room acoustics. Therefore, this section’s evaluation was based on our observations and data gathering of the existing/actual design and settings of TES in districts in the Lower Mainland of Vancouver, British Columbia and from other literature, in order to understand the associated conflicts.  The characteristics of twenty-six TES presented in Table 2.2 in chapter 2 show that all TES are of traditional design, which means they are built to look like industrial workshops made of regular constructional materials (concrete, bricks and steel ceilings). This indicates that TES were not built to be like regular classrooms; they have higher ceilings, larger room areas and other related settings and equipment like machines and dust extractors. In fact, the ceiling height in TES ranged from 3.3 to 10.5 m, floor area ranged from 104 to 312 m2 and the room volume ranged from 440 to 3281 m3.      75 In some TES, this whole area could be occupied with machines only, with no specific area for teaching purposes. However, in other TES, a part of this area represents the industrial zone that has all needed equipment and machines, while the other part, which may represent 15% of the TES, is the teaching zone. In most TES this zone is open to the industrial section and not separated with any walls or partitions. In very few TES, we observed a totally separated classroom on the second floor of the TES that is sometimes used for written exams and in-classroom projects.  Surprisingly, two TES were found to be converted TES, which means that they were built and used as classrooms for years and then turned totally or partially into TES; examples are WR2 (104 m2) and WS4 (232 m2), both of which have low ceilings and low ventilation.   Moreover, as is shown in Table 2.2, thirteen of the TES have high ceiling and high ventilation. The largest TES is MB1, which is also one of the eight new TES.  The floor in most TES is made of concrete, while the walls in some TES were made of two different types of materials, such as bricks and concrete, or concrete and dry walls.    Noise-control measures were obvious in twelve TES; these include sound-absorbing materials on the walls, and/or acoustic tiles covering ceilings, but they were old TES (WR1, WR3, WR4, WS1, WS3, WS4, MS1, MS3, MR2, WR6, WS5, MS4).    None of the installed ventilation systems have noise-reduction measures such as duct silencers.  Dust collectors were found in the woodworking TES, but none was observed in the automotive TES or the metalworking TES. In six woodworking TES, dust collectors were not working ‘properly’ during the days of measurements, and two of them were removed to be replaced with newer systems.      76  The summarized characteristics of TES above indicate that TES design is much different from regular classroom design.   3.5.2 Background-Noise Levels (BNL) 3.5.2.1 BNL in unoccupied TES Figure 3.3 and Table 3.4 show the results of room average total, A-weighted BNLs for the twenty-six unoccupied TES.  Measured BNL ranged from 41 – 68 dBA (mean=54 dBA; SD=6.7 dBA) when the ventilation systems only were in operation. These results indicate that the twenty-six TES have BNL higher than the 35 - 40 dBA criterion of unoccupied core learning spaces (ANSI, 2009).   Figure 3.3: Measured total, A-weighted room-average background noise levels (BNL in dBA) in twenty-six unoccupied TES with ventilation systems only in operation. Also shown are the ANSI S12.60-R2009 criteria for classrooms (BNL ≤ 35 or 40 dBA, depending on room volume).   35    77  Table 3.4: Variation of room-average background noise levels (BNL, dBA) for unoccupied and occupied TES in different conditions.   In addition, average total, A-weighted BNL in the eight new (unoccupied) TES (WB2, WR2, WS1, AR1, AR2, AB1, MS1, MB1) was up to 3 dBA higher than the BNL in the eighteen old TES. Average BNL in the unoccupied automotive TES is the highest among the three types of TES. Figure 3.4 and Table 3.4 show that in the thirteen TES with dust collectors operating, average total, A-weighted BNLs ranged from 64 to 82 dBA (mean=70 dBA; SD=5.4 dBA), up to 24 dBA higher than when they were not operating, and up to 42 dBA higher than the applicable ANSI S12.60-R2009 criterion (ANSI, 2009).    Table 3.5 shows that there is a moderate negative (r = -0.4) linear relationship between sound absorption in TES and its BNL, which means that TES with sound-absorbing materials on BNL condition on measurement N Min, dBA Max, dBA Average, dBA SD, dBA Unoccupied TES Ventilation on (only) 26 41 68 54 6.7 Ventilation + Dust collector on 13 64 82 70 5.4 Ventilation on + Dust collector off 13 41 68 54 6.9 TES age  Old TES   (TES  > 10 years) 18 41 63 53 6.4 New TES (TES  < 10 years) 8 48 68 56 7.2 Occupied TES All types 17 71 91 85 5.6 Wood TES only 9 84 91 87 2.4 Metal TES only 6 71 90 81 7.4 Automotive TES 2 82 91 87 6.3    78 the walls or acoustic tiles on the ceilings, have BNLs lower than BNLs in TES without sound absorption.      Table 3.5: Major determinants of background noise levels in all unoccupied TES when ventilation system only on. Determinants for BNL N Average Min Max SD Correlation, r Sound absorption With (+), Without (-) 26 - - - - -0.4 TES age, years 26 26 3 86 23.9 -0.4   It is also shown that there is a negative relationship (r = -0.4) between the increasing age of the TES and its lower BNL (Table 3.5). This indicates that the settings of the new TES influenced the generation of higher BNL than in the old TES. The ventilation systems installed in Figure 3.4: Room–average total, A-weighted background-noise levels (BNL in dBA) in thirteen unoccupied TES with ventilation systems on, and dust collectors on and off. Also shown are the ANSI criteria for classrooms (BNL ≤ 35 or 40 dBA, depending on room volume). 35    79 the new TES generated higher noise levels, the large areas of the new TES, and/or most of the new TES have no noise control measures installed yet.  More information about how that measured BNL in TES fluctuate over sound frequency (Octave-band frequency) are shown in the next figures and paragraphs from a number of examples of the twenty-six measured TES.  Figure 3.5 shows examples of the measured high BNLs at each octave-band frequency (125 Hz-8kHz) when ventilation only was on in two unoccupied TES (a woodwork and an automotive TES) in Richmond school district.  Results show that BNLs in both TES are higher than the criteria for unoccupied classrooms. BNLs at middle frequencies (250 Hz -1 kHz) were the highest (38.8-46.5 dBA) for both TES. These two TES represent an example of all TES that have no noise- control systems or sound absorbing materials.  Figure 3.5: Measured background noise levels (BNL in dBA) at octave-band frequencies (125 Hz-8 kHz) in two unoccupied large TES with ventilation systems only on. Also shown are the ANSI criteria for classrooms (BNL ≤ 35 or 40 dBA depending on room volume).  35    80 Figure 3.6 shows another example of the measured high BNLs in each octave-band frequency (125Hz – 8kHz) when ventilation was on and dust collector was on and off in one unoccupied woodwork shop. The figure shows that BNLs at middle and high frequencies were higher than the 35-40 dBA criteria for unoccupied classrooms in both conditions. BNLs were even higher at all frequencies when dust collectors were turned on.    Figure 3.6: Measured background noise levels (BNL in dBA) at octave-band frequencies (125 Hz-8 kHz) in unoccupied large woodwork TES  (WS1) with ventilation systems on, and dust collectors on and off. Also shown are the ANSI criteria for classrooms (BNL ≤ 35 or 40 35    81 3.5.2.2 BNL in occupied TES BNL was also measured in seventeen occupied TES with shop equipment and machines in operation. The remaining nine TES did not participate in these measurements. Total, A-weighted BNLs ranged from 71 – 91 dBA (mean=85 dBA; SD= 5.6 dBA) in the seventeen occupied TES (Figure 3.7 and Table 3.4). These values were up to 46 dBA higher than the standards of ANSI S12.60-R2009 for classrooms.                35 Figure 3.7: Room-average total, A-weighted background-noise levels (BNL in dBA) in seventeen TES when unoccupied (ventilation system only in operation), and occupied and in normal operation. Also shown are the ANSI criteria for classrooms (BNL ≤ 35 or 40 dBA, depending on room volume) (ANSI, 2009).    82 3.5.2.3 Specific tasks and tools/machines noise Individually noise was measured during the operation of a number tasks, tools and machines. Measurements were carried out over the whole period of each specific task involving the use of any of the tools.   Table 3.6 shows the measured noise level for five common tasks and ten machines in all TES. Results showed that tools generated noise that ranged from 80 to 100 dBA. The lowest noise levels were during hand sanding with sanding paper, and the highest recorded noise level was from the planer machine. Grinding metals and hammering can generate noise levels up to 90 and 91 dBA, respectively.  Wood cutting processes generated noise levels that varied from 80 to 90 dBA.  A Computerized Numerical Control (CNC) machine that is used to carve designs/shapes on wood surfaces generates very high noise levels, which reach up to 98 dBA.   Table 3.6: TES tasks and tools noise levels (dBA) and process duration (minutes). Task Tool Minutes Noise levels range, dBA Reduce wood thickness Planer machine 1-3 93-100 Cutting for design CNC machine 3-10 93-98 Grinding Angel grinder 1-2 87-90 Sanding Sanding belt 1-2 87-90 Cutting Band saw 1-2 86-90 Cutting Arm saw 1-3 86-90 Hammering Hammer 6-8 80-91 Cutting curves Scroll saw 1-2 80-85 Cutting Table saw 0.5-1 81-84 Sanding Orbital sander 1-3 78-85 Sanding Paper sanding 6-10 74-80     83  In summary, in all TES and in all conditions of measurement, BNL exceeded the applicable classroom acceptability/design criteria, receiving a failing grade.  Using a number of tools and machines in TES is associated with generating very high noise levels that increase the levels of noise in the occupied condition.   3.5.3 Reverberation time (RT) Figure 3.8 shows the measured room-average, mid-frequency (500 – 1000 Hz) RTs (EDT) in the twenty-six TES. It was found that twenty-three of the TES have RTs higher than the 0.6 and 0.7-s criteria for large core learning spaces (ANSI, 2009), and only three TES (WS4, MR2, MR4) have RTs meeting the classroom criteria.    On the other hand, half of the TES have RTs higher than the 1-s criterion for industrial rooms (Warnock, 1980). For instance, woodwork TES WB2 has an RT of 3.9 s and automotive TES AB1 has an RT of about 2.6 s, while the other half have RTs that met the (Warnock, 1980) criterion. Moreover, results in Table 3.7 show that RTs among all TES ranged from 0.6 – 3.9 s, with an average of 1.2 s.  RTs are higher in TES with high ceilings (mean=1.3 s; SD= ± 0.9 s) than those with low ceilings (mean=1.1 s; SD= ± 0.4 s). This relationship between the height of the TES ceiling and RT is also illustrated in Figure 3.9.         84   Figure 3.8: Measured room-averaged mid-frequency reverberation times (RT in s) in twenty unoccupied TES. Also shown are the criteria for classrooms (RT ≤ 0.6, ≤ 0.7 s) and industrial workshops (RT ≤ 1 s).   Additionally, it was found that the fourteen TES without sound-absorbing materials have RT (mean=1.5 s; SD= ± 0.8 s) values that ranged from 0.7-1 s higher than RTs (mean=0.8 s; SD= ± 0.2 s) in the twelve TES that have sound-absorbing materials (Figure 3.10). Table 3.7 also shows that measurements in new TES indicated higher RTs (mean=1.7 s; SD: ± 1.1 s) than in old TES (mean=0.9 s; SD= ± 0.3 s).           0.7 0.6    85  Table 3.7: Reverberation times (RT) for unoccupied TES and calculated descriptive quantities according to different conditions of TES. RT different conditions of TES N Reverberation times, Seconds Min Max Average SD All TES 26 0.6 3.9 1.2 0.7 High ceiling TES (height > 5 m) 13 0.7 3.9 1.3 0.9 Low ceiling TES  (height < 4 m) 13 0.6 2 1.1 0.4 New TES  ( TES > 10 years) 8 0.8 3.9 1.7 1.1 Old TES    ( TES < 10 years) 18 0.6 1.5 0.9 0.3 No/little sound absorption 14 0.6 3.9 1.5 0.8 With/some sound absorption 12 0.6 1.2 0.8 0.2    Figure 3.9: Variation of RT with ceiling height.        86   Figure 3.10: Variation of RT with sound absorbing materials.   Indeed, Table 3.8 shows the results of testing the relation between the main investigated determinants and reverberation time variation (increase or decrease). A positive (r = + 0.2) linear relationship was indicated between the ceiling height and RT, which confirms that TES with higher ceiling might have higher RT than TES with lower ceilings. Another positive (r = + 0.11) linear relationship was found between the volume of the TES and its RT, which means that the larger the TES the higher the RT.   Moreover, a negative (r = - 0.6) linear relationship was indicated between existence/lack of sound absorption materials in the TES and its RT, which means that TES without sound absorbing materials have higher RT.        87   Table 3.8: Major determinants related to reverberation times RT. Determinants for RT N Average Min Max SD Correlation, r Ceiling height, m 26 5.8 3.3 10.5 1.71 0.2 Room volume, m3 26 1304.7 356.5 3281.25 616.9 0.111 Sound absorption With (+), Without (-) 26 - - - - -0.6 TES age, years 26 26 3 86 23.9 -0.6    Figure 3.11 shows examples of the high measured octave-band RT (EDT) in the unoccupied condition in three different types of TES from one high-school in Richmond district. Results showed that RTs at all frequencies were higher than the acceptability/design criteria for both core learning spaces and industrial rooms. The metalwork TES has the highest RT values, ranging from 1.7 – 2.0 s at middle frequencies (500 - 4000 Hz).   Figure 3.12 shows another example of high octave-band RT from two new TES that have very high ceilings and sound-reflective walls. RT values in these TES are much higher than 1.0 s at all frequencies. In the wood TES, RT was up to 4.0 s at the middle frequency (1 kHz), which was considered the highest RT.  On the contrary, Figures 3.13 and 3.14 show that there are few TES with RTs less than or equal to the maximum RT (1.0 s) for industrial workshops at middle frequencies (500 Hz – 1 kHz) and higher frequencies (2 kHz – 8kHz).       88   Figure 3.11: Measured octave-band reverberation times (RT in s) in three different types of TES: Metal TES, Wood TES, and Automotive TES in Richmond school district. Also shown is the Warnock 1-s and ANSI 0.7-s criteria for unoccupied conditions.   Figure 3.12: Measured octave-band reverberation times (RT in s) in two different types of TES: Wood TES, and Automotive TES in Burnaby school district. Also shown is the Warnock 1-s and ANSI 0.7-s criteria for unoccupied conditions.     89  Figure 3.13: Measured octave-band reverberation times (RT in s) in a metalwork TES, in Burnaby school district. Also shown is the Warnock 1-s criterion for unoccupied conditions.     Figure 3.14: Measured octave-band reverberation times (RT in s) in a metalwork TES and a woodwork TES, in Surrey school district. Also shown is the Warnock 1-s criterion for unoccupied conditions.      90  In summary, measured RT values in most TES are higher than the acceptable/design criteria for classrooms and for industrial workrooms. Only 50% of the TES have RT values acceptable for unoccupied industrial workshops. In addition, correlation tests showed that RT is affected by different characteristics of TES room settings, including ceilings height, room volume and the installation of sound absorbing materials.   3.5.4 Speech intelligibility index (SII)  This section presents the results of SII in twenty-six unoccupied TES and seventeen occupied TES. The SII results from the occupied TES were based on the measured BNL during the normal operation of each occupied TES.  All presented SII results were compared with the suggested SII/SIQ scale (Table 3.2). 3.5.4.1 SII in unoccupied TES Table 3.9 shows an example of the calculated SII and speech intelligibility quality (SIQ) for three unoccupied TES with ventilation only in operation. SII was measured for four vocal outputs (‘normal’, ‘raised’, ‘loud’, and ‘shout’) at three different distances (1 m, 2 m, 4 m) from the speech source. It shows how the SII and SIQ varied with distance.   As shown in Table 3.9, SIQ in WS3 is found to be ‘fair’ at 4 m, ‘good’ at 2 m, and ‘excellent’ at 1 m for the four vocal outputs, and received a ‘pass’ grade.  The highest SII value always occurred at ‘loud’ and ‘shout’ vocal outputs. However, SII in AB1 TES corresponded to ‘poor’ and ‘fair’ SIQ at 4 m, ‘fair’ to ‘good’ SIQ at 2 m, and ‘good’ to ‘excellent’ SIQ at 1 m. Of    91 course, the highest SII resulted at the shortest distance (one meter) from the source or at high vocal outputs ‘loud’ and ‘shout’.   Table 3.9: Speech intelligibility index (SII) and speech-intelligibility quality (SIQ) values for three unoccupied TES with ventilation system only in operation, as a function of vocal output, at three different distances from the speech source. TES Speech Intelligibility Index  (SII) D, m Speech Intelligibility Quality (SIQ) WS3 Normal Raised Loud Shout 1m 0.88 0.89 0.9 0.9 Excellent Excellent Excellent Excellent 2m 0.68 0.72 0.73 0.73  Good Good Good Good 4m 0.51 0.56 0.58 0.59 Fair Fair Fair Fair MR1 Normal Raised Loud Shout 1m 0.6 0.72 0.77 0.79 Good Good Excellent Excellent 2m 0.37 0.52 0.6 0.63 Poor Fair Good Good 4m 0.24 0.39 0.48 0.51 Bad Poor Fair Fair AB1 Normal Raised Loud Shout 1m  0.73 0.78 0.79 0.8  Good  Excellent  Excellent Excellent  2m  0.47 0.57 0.61 0.62  Fair  Fair  Good Good  4m 0.33 0.43 0.47 0.48 Poor Poor Fair Fair  Table 3.10 shows the results for all twenty-six unoccupied TES. Twenty-one TES received ‘passing’ grade; SIQ in these TES was ‘good’ or better with ‘normal’ or ‘raised’ voice. However, five TES received a ‘failing’ grade; where SIQ was ‘poor’ or ‘fair’ with ‘normal’ or ‘raised’ vocal outputs; a ‘loud’ or ‘shout’ vocal output was needed for ‘good’ quality.     92 Table 3.10: Room-average speech intelligibility index (SII), speech-intelligibility quality (SIQ) and Pass (P)/Fail (F) ratings for twenty-six unoccupied TES with ventilation system only in operation, as a function of vocal output. TES Vocal Output Overall SIQ P/F TES Vocal Output Overall SIQ P/F *‘NL’ *‘RS’ *‘LD’ *‘ST’ ‘NL’ ‘RS’ ‘LD’ ‘ST’ WB1 0.69 0.75 0.82 0.86 ’good’-‘excellent’ P AB1 0.47 0.57 0.61 0.62 ‘fair’-‘good’ F WB2 0.21 0.39 0.53 0.6 ’bad’-‘fair’ F MS1 0.76 0.76 0.85 0.85 ‘excellent’ P WR1 0.56 0.63 0.65 0.65 ‘fair’-‘good’ P MS2 0.74 0.77 0.79 0.79 ‘good’-‘excellent’ P WR2 0.53 0.61 0.64 0.65 ‘fair’-’good’ P MS3 0.86 0.88 0.89 0.89 ‘excellent’ P WR3 0.64 0.7 0.76 0.79 ’good’-‘excellent’ P MR1 0.37 0.52 0.6 0.63 ‘poor’-‘good’ F WR4 0.72 0.77 0.82 0.84 ’good’- ‘excellent’ P MR2 0.84 0.86 0.86 0.86 ‘excellent’ P WR5 0.55 0.61 0.67 0.71 ‘fair’-’good’ P MR3 0.48 0.54 0.59 0.61 ‘fair’-‘good’ F WS1 0.76 0.76 0.85 0.85 ‘excellent’ P MR4 0.7 0.8 0.84 0.85 ‘good’-‘excellent’ P WS2 0.68 0.72 0.73 0.73 ‘good’ P WR6 0.56 0.66 0.7 0.71 ‘fair’-’good’ P WS3 0.68 0.72 0.73 0.73 ‘good’ P WS5 0.74 0.77 0.78 0.78 ‘good’-‘excellent’ P WS4 0.84 0.87 0.87 0.87 ‘excellent’ P MS4 0.78 0.78 0.78 0.78 ‘good’-‘excellent’ P AR1 0.34 0.52 0.66 0.72 ‘poor’-‘good’ F MB1 0.53 0.73 0.89 0.95 ‘good’-‘excellent’ P AR2 0.62 0.69 0.72 0.72 ’good’ P AS1 0.68 0.79 0.84 0.85 ‘good’-‘excellent’ P *[NL: normal; RS: Raised; LD: loud; ST: Shout]    93 3.5.4.2 SII in occupied TES Table 3.11 shows the results for the seventeen occupied TES in normal operation. Nine TES received ‘failing’ grade; SI quality in these TES was ‘bad’, ‘poor’ or ‘fair’ with ‘normal’ or ‘raised’ vocal outputs. In six TES, SIQ was ‘good’ with ‘raised’ vocal output, and received a ‘passing’ grade. Sixteen TES have ‘good’ or ‘excellent’ at ‘shout’ vocal output.  Table 3.11: Room-average speech intelligibility index (SII), speech-intelligibility quality (SIQ) and Pass (P)/Fail (F) ratings for seventeen TES when occupied and in normal operation, as a function of vocal output. TES Vocal Output Overall SIQ P/F TES Vocal Output Overall SIQ P/F ‘NL’ ‘RS’ ‘LD’ ‘ST’ ‘NL’ ‘RS’ ‘LD’ ‘ST’ AB1 0.17 0.31 0.43 0.53  ‘bad’-‘fair’ F WS2 0.37 0.54 0.67 0.72 ‘poor’- ‘good’ F WB1 0.69 0.75 0.82 0.86 ‘good’-‘excellent’ P WS3 0.47 0.66 0.80 0.85 ‘fair’- ‘excellent’ F WB2 0.29 0.46 0.57 0.61 ‘bad’-‘good’ F WS4 0.45 0.64 0.79 0.86 ‘fair’- ‘excellent’ F WR5 0.33 0.51 0.64 0.70 ‘poor’-‘good’ F MS1 0.38 0.57 0.72 0.80 ‘poor’-‘excellent’ F WS1 0.41 0.60 0.75 0.83 ‘poor’-‘excellent’ P MS2 0.27 0.41 0.59 0.72 ‘bad’- ‘good’ F WR6 0.33 0.51 0.64 0.7 ‘poor’-‘good’ F MS3 0.49 0.68 0.82 0.88 ‘poor’-‘excellent’ P MR4 0.43 0.62 0.77 0.83 ‘poor’-‘excellent’ P WS5 0.38 0.56 0.7 0.77 ‘poor’-‘excellent’ F MB1 0.53 0.73 0.89 0.95 ‘poor’-‘excellent’ P MS4 0.33 0.53 0.68 0.76 ‘poor’-‘excellent’ F AS1 0.68 0.79 0.84 0.85 ‘good’-‘excellent’ P            94 3.5.5 Reduction of sound level with distance doubling (DL2) Figure 3.15 shows an example of the plotted spatial-decay curve for the measured total, A-weighted sound-pressure levels, and the best-fit logarithmic-regression curve and equation, for a wood TES (WB1) with floor-plan area of 312.5 m2. The resulting DL2 for WB1 is 2.3 dB/distance doubling. By comparing this result to the Ondet & Sueur (1995) criterion (≥ 3.2 dB/distance doubling for these areas) this shop is considered as a ‘reverberant' industrial room. The measured DL2 values in all twenty-six TES are shown in Table 3.12. Values varied from 0.5 - 3.8 dB/distance doubling. After comparing the results with the criteria (Ondet & Sueur, 1995) as a function of the floor area of the TES, twenty-two TES had DL2 values smaller than the criteria, received ‘failing’ grade and are considered as ‘reverberant’ rooms, containing insufficient acoustical treatment. However, four TES had acceptable DL2 and are considered as ‘acoustically treated’ (passing grade).                  Figure 3.15: Measured total, A-weighted sound-pressure level (SPL in dBA) spatial-decay curve for a wood TES (WB1), with logarithmic regression line and equation, corresponding to DL2 = 2.9 dB/distance doubling.    95   Table 3.12: Measured DL2 values (in dB/distance doubling) and pass/fail ratings in twenty-six TES and comparison with Ondet & Sueur (1995) acceptability/design criteria. TES Area, m2 DL2 TES Area, m2 DL2 Measured Standard Pass/Fail Measured Standard Pass/Fail WB1 313 2.3 3.2 Fail AB1 200 2.4 3 Fail WB2 200 2.2 3 Fail MS1 233 2.2 3.1 Fail WR1 210 2.5 3 Fail MS2 240 1.5 3.1 Fail WR2 104 2 3 Fail MS3 220 2.9 3 Fail WR3 312 3.1 3 Pass MR1 200 2.5 3 Fail WR4 254 2.6 3.1 Fail MR2 305 3.1 3.2 Fail WR5 217 1.9 3 Fail MR3 108 1.3 3 Fail WS1 230 3.9 3.1 Pass MR4 168 2.7 3 Fail WS2 210 2.4 3.1 Fail WR6 199 0.5 3 Fail WS3 200 2.6 2.6 Pass WS5 150 2.1 3 Fail WS4 233 3.8 3 Pass MS4 110 1.8 3 Fail AR1 254 2.7 3.1 Fail MB1 313 1.2 3.2 Fail AR2 263 2.9 3.1 Fail AS1 188 0.8 3 Fail     3.6 Discussion The objective of this chapter was to evaluate the acoustical quality and conflict in TES. It was to understand the design/settings of these unique learning and working environments and how they would affect the acoustical characteristics. In fact, the results indicated that poor acoustical conditions and a serious acoustical conflict exist in the investigated TES; they    96 received failing grades or had unacceptable values for most of the related acoustical characteristics. In particular, the acoustical evaluation of unoccupied TES as classrooms showed high and unacceptable BNL and RT in most of the TES; the acoustical evaluation of the TES as industrial workshops found unacceptable RT and DL2 results.  Indeed, the acoustical conditions in the TES when used as industrial rooms are generally unacceptable for their use as classrooms (according to the DL2 results, though a few were satisfactory as classrooms according to the SII results).  Making TES acceptable as industrial rooms would not resolve the conflict.    The following parts of this section discuss the findings of each acoustical characteristic and the associated TES factors (e.g. TES design, constructional materials, ceilings heights). At the same time, a comparison between our findings and previous investigations in the same area is addressed.   3.6.1 Background noise levels (BNLs) BNL in all TES were up to 42 dBA greater than the allowable ANSI S12.60-R2009 criteria for unoccupied classrooms. These findings comply with previous investigations (Pekkarinen and Viljancn, 1991; Celik and Karabiber; 2000, Dockrell and Shoeld, 2006; etc.) as they indicated BNL higher than the maximum allowable criteria for empty “regular” classrooms (ANSI S12.60-R2009). A number of factors and determinants related to TES design and settings were found to be associated with the high BNLs.   First, the mechanical services, including ventilation systems and dust collectors, were found to be the major sources for the high background noise levels in all unoccupied TES.  The highest measured BNLs ranged from 60-68 dBA with ventilation on, and 70-82 dBA with both    97 ventilation and dust collector in operation. In fact, our observations indicated that the current installed ventilation systems and dust collectors were not properly controlled for noise, but that the ventilation systems were working reasonably to maintain the required general air quality in TES. By considering TES as classrooms or learning spaces, our findings support the findings of Hodgson et al., (1999) for high BNLs in unoccupied classrooms due to ventilation systems, and their recommendations to ensure ventilation systems with reduced noise are installed in any new or renovated classrooms. This suggests applying noise control at the source, which is the ventilation system. Indeed, our investigations also indicated that even though there are 13 TES with some sound control measures (e.g. sound absorbing materials on the walls, ceiling acoustic tiles) the BNLs of their ventilation systems are still higher than the maximum allowable level for unoccupied classrooms and core learning spaces. Therefore, in TES, an effective way to reduce the noise of ventilation to acceptable levels could be by applying noise control means to the ventilation ducts while making sure that the efficiency of the ventilation systems will not decrease to unacceptable levels.  In addition, the age of TES was found to be another factor, which is mainly related to the design and the construction materials used in the TES. Our investigation showed that there are 8 new TES (3-10 years old). The results indicated that these eight new TES have BNLs higher than the background noise levels in the older TES. In particular, these new TES have three things in common: untreated acoustically, high ceilings (5.5 -11 m) and reflective walls, which make them different from most of the old TES. This outcome is contrary to the findings of Picard and Bradley, (2001) and Shield and Dockrell, (2004) regarding better reduction of background noise in new or modern school classrooms than in old or classic schools. Their    98 findings could be more relevant to new classrooms that are only built for one specific/clear purpose (teaching), which are provided with effective noise control means through their designs, sizes, and by the installation of sound absorbing materials.    Indeed, this finding is surprising, because new TES were supposed to be designed better and have more effective noise control systems in them than the old TES. Therefore, classrooms and TES designers should set acoustic requirements as a first priority of their planning. Measurements of BNLs in the unoccupied condition give an indication of how bad or reasonable BNL would be in occupied condition when teachers and students are present and machines are in operation. A number of authors (Hodgson, 1994; Celik and Karabiber, 2000) suggested that a typical background noise level of 35 dBA in an unoccupied classroom could increase to 56 dBA in occupied conditions or by students’ presence in the classroom.  The acoustical evaluation of the occupied condition showed that BNLs in the seventeen occupied TES when teachers and students were present ranged from 68 – 76 dBA during the first 10 to 15-minute introduction session of the class and with no dust collectors and no machines in operation. This finding, in particular, could comply with many previous authors (Hodgson et al, 1999; Shield and Dockrell, 2003; Picard and Bradley, 2001;) who found that the noise resulting from student and teacher activities in “regular classrooms” reached up to 70 dBA.   Moreover, Cunniff (1977) reported that, in industrial-working rooms, the poor acoustical design/treatment of TES, in addition to the type of activities, machines noise, machines numbers and sizes, are the main factors related to the high BNLs. Our results showed that when teachers and students were working and machines were under operation in TES, BNLs ranged    99 from 71 to 91 dBA and were about 31 dBA higher than BNLs in the unoccupied condition and about 25 dBA higher than when teachers and students are present but not working.  In fact, in occupied woodworking TES the recent results of background noise levels could be the highest (91 dBA) due to the dust collector noise and tools/machine noise. This also supports Lankford and West (1993) who found that noise levels in occupied woodwork TES reached 85 dBA and more in other cases when both ventilation and machines were in operation.    In addition, our measurements of tool noise showed that tools and machines used in TES generate noise levels reaching up to 101 dBA. Impulse noise generated form hammering. It was also found that grinders, orbital sanders and arm saws generate noise up to 91 dBA, and that this matches the findings of Jayjock and Levin (1984), Singh et al (2009) and Bejan et al (2011) who concluded that these tools can generate the highest noise levels (> 90 dBA).  The planer machines in woodwork TES generate noise levels up to 101 dBA. These machines are mainly used for trimming wood boards to a consistent thickness through their length, and making them flat on both surfaces. The observed and investigated types of planer machines in TES were of the old types, which are of very heavy construction, made of steel, and are driven by powerful motors. The powerful motors generate high levels of noise, the noisiest stages when using planer machine include inserting and compressing/cutting the boards.   Consequently, the measured high BNL is associated with teachers’ high voice levels. Noise from ventilation systems and other mechanical equipment in classrooms or any learning environment is reported as a serious problem for teachers and students; teachers always tend to raise their voices to maintain the +10 dB signal-to-noise ratio necessary for good speech intelligibility (ASA, 2000). It was also reported that teachers’ voice levels could reach up to 80    100 dBA during teaching in occupied classes in order to be heard (Hodgson et al., 1999 Shield and Dockrell, 2003; Picard and Bradley, 2001; Dockrell and Shield 2006). During the introductory minutes in TES, BNLs reached up to 76 dBA on average. This represents the teacher voice when ventilation only is in operation, as they tend to talk louder than in normal situations to be heard by their students, which consist with the previously reported findings. In fact, this situation was found to be much worse when all machinery was in operation and a lot of activities were taking place, at which background noise levels could reach up to 91 dBA. In situations like this, teachers tend to shout to be heard by their students even at short distances in some TES, as they try to cope with the noise levels surrounding them.  Furthermore, high BNL was also associated with high noise exposure levels (Lex) among the teachers and students in the occupied TES, as shown in the next chapter.   3.6.2 Reverberation time The results obtained for reverberation times in classrooms and industrial- workrooms indicated high and unacceptable values in many of the TES. RT results showed that 23 TES were unacceptable as classrooms and 13 of them were unacceptable as industrial workrooms.  The RT results are associated with some factors that include the lack of suitable noise-reduction/absorption design and control measures – in particular high ceilings, the large room volume and hard/sound-reflecting surfaces.   In fact, correlation tests confirmed that TES with high ceilings (5.5-11 m) and large room volumes (1300 – 3200 m3) provided higher reverberation times than TES with lower ceilings and smaller room volumes.       101  Moreover, TES with sound absorbing materials on the walls and acoustic tiles covering the ceilings have lower RT values than TES without sound absorbing materials.  In fact, the highest values of RT reached 2.5 and 3.9 seconds in two particular TES, AB1 and WB2. These two TES are new, acoustically untreated, have ceilings up to 7 meters high, and have sound-reflective surfaces made of concrete. The worst case was also observed here with two reflective walls (or the floor and ceiling in other TES) facing each other; sound bounces back and forth between these two walls producing flutter echoes that negatively affect speech intelligibility (ASA, 2000). This is strongly confirmed by our findings that the resulting high RTs interfere with speech intelligibility and result in a ‘noisy’, uncomfortable work/learning environment. These two TES also provided the highest background noise levels due to their special designs and settings as described earlier.   On the contrary, our results showed that only 13 TES have acceptable RT values that are equal to or lower than the maximum allowable RT for industrial workshops (Warnock, 1986), while only 3 of them have RT values that are acceptable for classrooms (ANSI, 2009). For example, WS4 TES is very old, has low ceilings that are not higher than 3 meters, has some walls treated with sound absorbing materials, and the TES area is occupied with machines and some equipment. Moreover, there is a possibility that this woodworking shop was built to be a classroom and then converted to woodwork TES. The design of this TES has three different heights of ceiling with different acoustical treatments; one part (high ceiling) was 50% covered with acoustical tiles, and the second part (low ceiling) with foam (Figure 3.16 and 3.17).     102                      Figure 3.16: An image of the old WS4 TES. This shows a wide view of the TES and the type of high ceiling in one part of the room. Figure 3.17: An image of the old WS4 TES. This shows the type of low ceiling in the middle section of the room.    103 3.6.3 Speech intelligibility index (SII) Due to the high BNLs and RTs, SIIs were unacceptable in most of the seventeen occupied TES at ‘normal’ and ‘raised’ vocal outputs. However, in seven TES SII corresponded to ‘good’ or ‘excellent’ SI quality, and was acceptable, when a ‘shout’ vocal output was used, if at all.   The SII results indicated that teachers in most TES during class sessions have to raise their voices to ‘loud’ or ‘shout’ to be heard by their students due to the high BNL and RT. This supports Losso et al., (2004), who reported that in classrooms with RTs higher than 1 second and BNL higher than 51 dBA, teachers raise their voices up to about 80 dBA at 10 feet (Markides, 1986) to achieve the recommended signal to noise ratio of +15 dB. In TES, we found that BNLs and reverberation times were much higher, which could encourage teachers to raise their voices and shout to up to 80 dBA or higher, resulting in difficult verbal communication (Kristiansen et al, 2013; Losso et al, 2004; Hodgson, 2004).   Moreover, sometimes short or low reverberation times in large classrooms could be a problem for verbal communication. The sound-absorptive ceilings in these classrooms could absorb teachers’ voices before they reach the students at the back of the classroom (ASA, 2000). This situation could be similar to some TES such as WS4, which has ceilings covered with sound-absorptive materials, causing the teacher to raise his voice or talk louder to be heard.   Applying this effort of talking in ‘loud’ or ‘shout’ voice level over longer periods is associated with serious voice problems (Sala et al., 2001) and adverse psychological effects among teachers, such as job-related stress (Winkworth and Davis, 1997; Kristiansen et al., 2013).     104  Furthermore, TES students apply more effort to primary learning tasks in these noisy working and learning environments (Slater, 1968). This negatively affects their speech perception, performance and concentration (Ando and Nakane, 1975; Crook and Langdon, 1974; Gumenyuk, et al., 2004), as they are more easily distracted by noise than adults (Dockrell and Shield, 2006; Crandell and Smaldino, 2000).    3.6.4 Reduction of sound levels with distance doubling (DL2) The investigation of TES as ‘acoustically treated’ industrial rooms by measuring DL2 in twenty-six unoccupied TES indicated that twenty-two TES are considered as ‘reverberant rooms’, in which DL2 values are not reduced efficiently with doubling of distance from the source and are not higher than minimum criteria. This could support the fact that in large or reverberant rooms the influence of fittings is very slight on the reduction of sound per doubling distance (Ondet and Sueur, 1995), which is the case in most of the reverberant TES. For instance, two TES had floor areas of 200 m2, high RT and no sound-absorbent materials were installed in them, their DL2 was very low and unacceptable to its standard (3 and 3.2 dB, respectively), and their fittings could not affect the room DL2.  On the other hand, only four TES received a passing grade and are considered ‘acoustically treated’. For instance, in WS4 RT is 0.6 s, it has a floor area of 233 m2, low and acoustically treated ceilings/walls, and is occupied with machines and equipment that might have a slight influence on its DL2, which was 3.8 dB and was acceptable as it is higher than the criteria of 3 dB according to its floor area according to Ondet and Sueur, (1995).     105  Although twelve TES have some noise control measures in them, DL2 tests showed that only four are treated acoustically. This indicated that the current sound control is not effective to reduce background noise levels and reverberation times in most of these TES. This demonstrates the importance to suggest more efficient control measures and better room acoustical design to provide the required reduction of noise and reverberation time in each TES.    3.7 Summary This investigation indicated the poor design of TES from the acoustical point of view to be used as industrial workshops or as classrooms. It was indicated that acoustical matters were not taken seriously during the planning and building of these TES, as is always the case in many other learning environments, which are supposed to be acoustically acceptable for better learning.  The difficulty to meet the criteria for the two different uses of TES (teaching and working) and the variety of designs and settings, resulted in poor acoustical conditions in most of the investigated TES.  Generally, the acoustical conflict exists because, TES failed to provide the required acoustical conditions for both purposes, as classrooms and as industrial workshops.   TES have unacceptable/high BNL and RT for unoccupied classrooms, and unacceptable DL2 and RT for industrial workrooms. During regular classes in TES, BNL are much higher than in unoccupied conditions due to student activities and machine noise.    106  Consequently, verbal communication quality during TES class was poor in general, which encouraged teachers to talk loudly, to shout in most cases, or to communicate with their students at distances less than 4 meters to be heard.   Furthermore, poor acoustical condition in TES could adversely affect the quality of learning and comfort, and the health of the students and teachers. It could cause distraction, which can easily affect student concentration; teachers could also suffer from serious hearing problems and voice fatigue because of the greater effort to raise their voice or shout in the class. Serious potential safety issues, including risk of accidents and injuries, could be increased when loud background noise masks their calls for help or alarm signals.    Finally, failure to meet the required acoustic criteria in the design of TES was expected, as these environments are intended for two different purposes of “working” and “learning”.  TES failed to provide the acceptable acoustical characteristics for both uses, by failing to meet the criteria for classrooms and industrial workshops. Therefore, an acoustical conflict exists in TES. A serious application of noise control measures must be recommended for these environments. It is important to consider the needs for each type of use and what is required in the design of such rooms.                107  4 Evaluation of the Student and Teacher Exposure to Noise and Airborne Hazards   4.1 Introduction This chapter represents the second evaluation phase of this study framework―that is, the evaluation of occupational exposure of teachers and students to noise and airborne hazards in TES relative to industrial exposure limits or permissible exposure levels. It consists of five sections, including the objective, occupational hazard exposure limits (OEL), materials and methods, results, and summary of the chapter. The following sections describe the procedures taken to accomplish this investigation.    4.2 Objective The objective of this evaluation is to explore and understand the difference in exposures to the potential occupational hazards in TES between TES teachers and students. To accomplish this objective, we measured the exposures of teachers and students to noise and airborne hazards (wood dust and welding fume). The results of each exposure were assessed for compliance with the EL - TWA 8hr and the action limits adopted in British Columbia. In fact, these limits might not be very appropriate to evaluate the students’ exposure to hazards with regards to their vulnerability to levels even lower than those limits. Therefore, the action limits were used for students exposure to these hazards.    108  4.3 Hazard exposure limits  4.3.1 Noise in TES The adjusted Leq for 6 hour duration of teachers exposure to noise is 86.2 dBA, and for 1 hour period of students’ exposure is 94 dBA. The action level (82 dBA) was also selected to assess if the exposure of teachers and students to noise were > 82 dBA at any time of their school-TES day. If results show that teachers and students were exposed to noise ≥ the action level, there will be a need for effective noise control measures in TES (WorkSafeBC, 2005).   Several studies found that exposure to < 83 dBA is safe to hearing for a maximum time of 8 hours a day (NIOSH, 1996; Bohle and Quinlan, 2000). Furthermore, the 24 hour total annual EPA recommended limit is 70 dBA to prevent NIHL and non-auditory effects (Cunniff, 1977).  These conclusions were also considered in the discussion of our research results.  4.3.2 Wood dust in TES ACGIH provided a OEL for inhalable wood dust of 1 mg/m3 as the OEL-TWA for regular working periods of 8 hr/day for workers in British Columbia, which include teachers in TES even though they work for 6 hr/day assuming that their exposure is zero for the rest of the time subtracted from 8 hours. Their exposures were also compared with the action level (50% of that TWA) for inhalable wood dust, which is 0.5 mg/m3 as it appropriate for all wood species.  However, for students who are more vulnerable to exposure to wood dust and have higher breathing rates, there is no special exposure limits or environmental standards for wood dust to use. Therefore, minimum regulated limit, which is the action level (0.5 mg/m3) was used    109 for compliance as they could be appropriate for young students.  To assure their safe exposure, their measured exposure levels should have to be < 0.5 mg/m3.  Results include exposures of teachers or students that are > 0.5 mg/m3, will require the need for wood dust control measures in woodworking TES.    4.3.3 Welding fume in TES OEL for total welding fume as TLV-TWA is 5 mg/m3 for 8 hours of exposure as adopted from ACGIH. However, from the walk-throughs and observations in TES, it is found that TES teacher and student exposure periods to welding fume were very short and ranged from 13 to 60 minutes during their time in TES, and ACGIH withdrew the STEL/Ceiling limits for short periods (15 minutes). Therefore, the action-level of 2.5 mg/m3 is used as the reference for exposure to total welding fume for short periods among teachers and students. Therefore, the accepted personal exposure concentration of total welding fume were to be < 2.5 mg/m3, taking into consideration and in the discussion the vulnerability of students to welding fume.  Finally, measured exposures that were > the action level suggested a proposal for control measures to reduce exposure to welding fume in TES (WorkSafeBC, 2003; ACGIH, 2011).   4.4 Materials and methods Personal and area sampling of noise and airborne hazards was conducted in 17 TES based on consent of participating schools, TES teachers and students (Table 4.1).    110  Table 4.1: Number of recruited TES, teachers and students. Measurement TES # [Type] Subjects # Noise-exposure levels 17 [9 W, 6 M, 2 A]* 17 teachers 17 students Wood dust 9 W TES 9 teachers 12 students Welding fume 4 M + 1 A 1 teacher 6 students * W: woodwork TES; M: metalwork TES; A: Automotive TES.   4.4.1 Evaluation of the personal exposure to noise in TES Personal exposure to noise was investigated in 17 occupied TES in the three school districts, including 9 woodworking TES, 6 metalworking TES, and 2 automotive shops. The personal noise exposure levels were measured among two or three subjects for 1-3 days of sampling in each TES. This involved a total of 17 teachers and 17 students. Personal exposure to noise was monitored during 6-hour/day for TES teachers and 1-hour/day for students during normal days of working and teaching in each TES. Fully charged and calibrated CEL 350 noise dosimeters (Casella USA) were used. Noise dosimeters were attached to the subjects’ shoulders (within the hearing zones), at the beginning of each sampling day for the teachers and at the beginning of the TES class for the students.  The starting time of sampling and subject codes, location and date were also recorded on a sampling sheet (Appendix D). The participants were asked to not touch, or remove the noise dosimeter from their shoulders during sampling. Results were compared with the WorkSafeBC limits of exposure to noise, as described in section 4.4.1.     111 4.4.2 Evaluation of the exposure to wood dust in TES 4.4.2.1 Personal exposure sampling  Personal exposure to wood dust was investigated in nine woodworking TES in the three school districts. The personal samples of wood dust were collected from one teacher and one or two student/s for 1-3 days of sampling in each woodworking TES. This involved nine teachers and twelve students; 48 personal samples of wood dust were collected.  This investigation was carried out during regular days of working and teaching in occupied woodworking TES and during woodworking processes. This sampling was based on the NIOSH 0500 method (Appendix G).    To monitor personal exposure to inhalable wood dust within the breathing zone, a fully-charged and calibrated personal sampling pump (SKC Universal PCXR4) with a flow rate of 2 liters/minute, connected to a pre-weighed (by microbalance Sartorius M5P), tared, polyvinyl chloride filter (25-mm diameter, 5-micron pore size in IOM sampler) in an environmentally controlled room (at 20 C  1 C and 50% ± 5% RH), was attached to each participant’s shoulder at the beginning of each sampling day for the teachers/students, and at the beginning of each TES class for the students. After that, the sampling pumps were turned on, and the starting time, flow rate and date were recorded on a special sampling sheet. The sampling sheet included subject code, filter weights, pumps number and location code.  At the end of the sampling period, the end time was recorded on the sampling sheet. The end flow rate of the pump was recorded and detected if it was within 10% of the flow rate at the beginning of the sampling period. After that, personal sampling pumps were turned off and collected. Filters    112 were taken to the lab in secured zip bags with labels on them, for post-weighing on a microbalance (Model: Sartorius M5P), but after being kept in controlled temperature and relative humidity room for a period of one day or two. Subtracting the previously determined tare weight from the post-weight determined the weight of dust deposited on each personal sample; this was used to calculate the particulate concentration as described by NIOSH 0500 method (1994) for gravimetric analysis (Appendix F). The concentration (mg/m3) of wood dust was calculated from the following equation assuming each sample contained 100% of wood dust:  Concentration =W2−W1 (mg)V (L)  ×  103, (mgm3 )        (4.1) [W1: filter’s pre-weight (mg); W2: filter’s post-weight (mg); V: Volume of air sampled in the room (Liter) = pump flow rate (L/minutes) x sampling time (minutes)]        The limit of detection (LOD) was also calculated (LOD = 3 x Standard deviation of the blank filter weights) and it was 0.1 mg/m3. Results for 6-hour exposure to inhalable wood dust were evaluated for compliance with the daily OEL-TWA = 1 mg/m3 for the teachers, and with the action limit = 0.5 mg/m3 for the students 1 hour exposure.   4.4.2.2 Area sampling Total area wood dust was collected in the nine woodworking TES in the three school districts. Sampling was carried out for 1-3 days in each woodworking TES. This resulted in a total of twenty area samples of wood dust. To monitor the background ambient wood dust during a    113 full-shift period of operation in TES, a fully charged and calibrated sampling pump with a flow rate of 2 L/min, using a pre-weighed, tared, polyvinyl chloride filter (25-mm diameter, 5-micron pore size, installed in an IOM sampler) was placed at an appropriate location that represents the whole area in each wood-working TES, which often was the middle or close to the machines zone but 2 meters away from any obstacle to air flow. At the beginning of each sampling day, the sampling pump was turned on, and the starting time, flow rate and date were recorded on the sampling sheet. At the end of the sampling day, the sampling pump was collected and put on hold; the end time and flow rate were recorded on the sampling sheet. The sampling pump was turned off after that. Filters were kept in zip bags with labels on them and shipped to the lab for post-weighing on a calibrated microbalance. Finally, to determine the weight of dust deposited on each filter, the previously measured tare weight was subtracted from the post-weight. NIOSH 0500 method for gravimetric analysis was used to calculate the particulate concentration as described above. Resulting wood-dust concentrations were compared with the action limit of 0.5 mg/m3.   Moreover, direct measurements of wood-dust concentrations were performed for specific tools and machines. These measurements were done using a calibrated TSI Dust-Trak 8530. This device was placed at different work locations in a number of woodwork TES. The device was used to record the dust generated from certain tasks and tools, including sanding, sawing, using lathe machines, planer machines and sanding papers throughout the period of each task. All readings were stored in the memory under a specific code/name/date and then uploaded to a computer in the lab.      114 4.4.3 Evaluation of the exposure to welding fume in TES 4.4.3.1 Personal exposure sampling Personal exposure to welding fume was measured in three metal TES and one automotive TES. The personal samples of welding fume were collected from one teacher and four students on 1-3 days of sampling. Personal sampling was only conducted during days of welding operations. This resulted in a total of nine personal samples calculated for welding fume concentration. The durations of welding operations that were monitored varied from 13 to 60 minutes. Sampling was carried out over these periods during TES classes. The reason for doing that is related to welding task characteristics in TES; this task is performed by few numbers of teachers and students in welding enclosed spaces and designated areas inside the TES. It is performed occasionally/infrequently and not in every class or during the entire day/class. Therefore, sampling was done during welding in each welding task period to monitor the exact exposure to the associated welding fume. At the beginning of the sampling a personal-sampling train (consisting of a charged and calibrated personal sampling pump, at a flow rate of 2 L/min, that was connected with flexible tubing to a pre-weighed 37-mm, 8-micron, cellulose-ester membrane in a 37-mm filter cassette) was attached to the subject’s collar and placed under (inside) the welding helmet within the breathing - respirator  zone to best represent the exposure; this followed the OSHA standard 1910-252, (1999) recommendation for the correct placement of an air-sampling cassette for welding fume (Ashby, 2002). After that, pumps were turned on at the same time that welding started. Starting time, flow rate and welding type were recorded on the sampling sheet. Subjects were recommended to not remove or turn off the    115 pumps during the sampling period while welding.  At the end of sampling, pumps were collected, the end time and flow rate were recorded, and pumps were turned off. Filters were collected in zip bags and sent to the lab for post-weighing, in order to conduct gravimetric analysis to determine the total particulate concentration according to NIOSH method 0500. The concentration (mg/m3) of welding fume was calculated using equation 4.1.  The limit of detection was also calculated from the blank filter weights, and was 0.02 mg/m3. Results were compared with the action level of 2.5 mg/m3.   4.4.3.2 Area sampling Area samples of welding-fume particulates were collected from two metal and one auto TES. Measurements were only conducted during 1-3 days of welding operations in the three TES. The total of the collected samples is five samples. At the beginning of the sampling day, a fully charged and calibrated sampling pump, at a flow rate of 2 L/min, was connected to a pre-weighted, 37-mm, 8-micron, cellulose-ester membrane in a 37-mm filter cassette. This sampling pump was fixed securely in an appropriate location in the welding area. Afterwards, the sampling pump was turned on at the start time of welding, and sampling information was recorded on the sampling sheet. At the end of sampling, the pump was collected, the end time and flow rate were recorded, and pumps were turned off.  Filters were kept securely capped in zip bags to be shipped to the lab for analysis. Concentrations of total particulates of welding fume were determined as described above for personal sampling.    116  4.5 Indoor air quality In addition to the sampling of airborne hazards, measurements of indoor air quality were conducted at the same time on each day of sampling. These included the measurement of CO2, temperature, pressure and humidity in the TES on 1-3 days of sampling. These factors affect the air-contaminant concentrations, and may also have effects on the sampling filters/instruments that were used. To measure the concentrations of CO2, a calibrated indoor-air-quality meter (direct measuring instrument) [TSI Q-Trak Plus 8551] was used. This instrument was also used to measure and record relative humidity (RH%) and temperature (C°) in the TES simultaneously. These parameters were measured for ten minutes, and three times (Start- Middle and End of the class) on each day of sampling in each TES. Finally, all recorded data were downloaded into a laptop through a TSI supplied software and averages were calculated for CO2, temperature and relative humidity for each TES.    4.6 Data and results analysis  All collected data and results were checked for accuracy by screening to clarify any errors or problems. Database structure was developed in excel for each variable and its measurement results including all related information and data gathered from sampling sheets, walkthrough surveys, floor plans and TES information.    Data were prepared for statistical analysis and included results of exposure monitoring, determinants of exposure (tasks, equipment, control measures, periods of tasks, subject).      117 Exposure measurements that are below the LOD were substituted with a constant value by dividing LOD by the square root of 2.  To determine typical exposures and their variability, the results were analyzed as follows: A) Descriptive statistical calculations to assess the exposure distribution (i.e. central tendency and spread included exposure averages over days of sampling, range of exposure levels detected, and the variation of the exposure levels from one TES subject to another):    Means/averages  Minimum and maximum  Standard deviation Results of exposures were tested for compliance with the selected appropriate exposure limits for noise, wood dust and welding fume.  B) To examine the effectiveness of the selected determinants of exposure on the measured exposure levels, preliminary exposure factors were analyzed by correlation (r) calculations to determine relationship between the variation in occupational exposure levels and period of exposure, type of tasks, current acoustical treatment, control systems for wood dust and welding fume.  Finally, results from this analysis were interpreted and tested if they fulfilled the objectives of this research or not. Further discussion of the analysis results included their significance if there is an impact on the collected sample and to what extent it would represent the participants’ long-term exposure in the same work environment.      118   4.7 Results 4.7.1 Noise personal exposure level  Personal exposure to noise was measured among seventeen teachers and seventeen students from the seventeen occupied TES. Measurements of personal exposure were taken on two to three different days of sampling during regular TES classes, and with equipment and machines in operation. Monitoring of teachers’ exposures to noise was conducted during a full-daily shift (6-hours), and during TES class periods (1-hour) for students.   Figure 4.1 shows noise-exposure results for seventeen TES teachers as the daily averages of LAeq-6hr. Results indicate that teachers were exposed to occupational noise levels that ranged from 75-91 dBA (mean= 83 dBA; SD= ± 4.16 dBA) for 6-hours of exposure. Four teachers, all from woodworking TES, were exposed to noise levels that exceeded the limit of 85 dBA, while ten of the teachers from varying types of TES were exposed to occupational noise ≥ 82 dBA.   Figure 4.2 shows results for noise exposure levels for seventeen students as the daily averages of LAeq-1hr. Results indicate that noise exposure levels for the seventeen students ranged from 79-100 dBA (mean= 86.7 dBA; SD= ± 5.9 dBA) for 1-hour of exposure. All of the seventeen students were exposed to noise levels ≥ 82 dBA. Two students from metalworking TES were exposed to noise levels ≥ 94 dBA/1 hr a day.       119  Figure 4.1: Average personal noise exposure (LAeq, 6 hr, dBA) among seventeen TES teachers. Also shown are the corrected limit of exposure ≤ 86 dBA/6-hours and the action level 82 dBA (Work Safe of BC, 1996).   Figure 4.2: Average personal noise exposure levels (LAeq-1hr, dBA) for seventeen TES students. Also shown are the corrected limit of exposure ≤ 94 dBA/1-hour and the action level 82 dBA  (Work Safe of BC, 1996).     86.2 94    120  Table 4.2: Variation of noise exposure levels among teachers and students with the descriptive characteristics according to different types of TES.  Table 4.2 shows how noise exposure levels among teachers and students varied according to the type of TES. Average noise exposure levels in woodwork TES were higher than those in metalwork and in automotive TES. The types of tasks involved in the woodwork TES were found to generate higher task noise than in other types of TES.  Figures 4.3 – 4.6 give more explanation and represent the common situations of teachers’ daily exposures to noise in the investigated TES, and how they vary over time due to different activities and tasks.  Figures 4.3 and 4.4 show examples that represent the high daily noise,  for two days of noise personal sampling for one woodwork teacher, from the readings of the noise dosimeter. Results in Figure 4.3 indicate that on the first day of sampling WS2 teacher Sample type Noise exposure levels, dBA  Teachers (6 hr-Leq)  Students (1 hr – Leq) N Min Max Average SD Teachers 17 75 91 83 4.16 Students 17 79 100 87 5.9 TES Type  Wood Teachers 9 79 91 85 4.03 Students 9 84 92 88 3.26 Metal  Teachers 6 75 84 80 3 Students 6 79 100 87 8.72 Automotive  Teachers 2 83 84 84 0.7 Students 2 79 82 81 2.12    121 was exposed to noise levels ranging from 61 to 102 dBA in the six-hour period. In fact, the lowest noise exposure levels correspond to the lunch hour inside the office when no students were present and no machines were in operation. However, this teacher’s noise exposure ranged from 85 to 102 dBA during teaching and working on a number of machines in this TES.      Figure 4.3: WS2 TES teacher noise exposure level on the first day of sampling. Figure 4.4: WS2 TES teacher noise exposure level on the second day of sampling.    122 In addition, Figure 4.4 shows that, on the second day of sampling, WS2 teacher was exposed to noise LAeq varying from 75 to 96 dBA during the first half of the day, which then dropped during break hour (11:00 -12:00) to about 63 dBA and increased after that during his last class to 99 dBA. Indeed, this teacher in particular has been exposed to the highest occupational noise level that is 91 dBA.  On the contrary, a teacher from metalwork TES in Richmond (MR4) was exposed to daily occupational noise levels lower than 85 dBA. His two days of exposure to noise are shown in Figures 4.5 and 4.6. This metalwork teacher starts his shift in the TES at 9:05 AM and finishes after 3:30 PM; the class has about twenty students from grades eight and nine who learn to do simple and small metal works, which do not generate very high levels of noise.            The teacher in this particular metal shop mostly carries out supervision duties, and is not involved in any heavy-duty tasks using machines. During the first half of the first day of sampling in the TES, noise exposure levels ranged from 68 to 90 dBA which then dropped to an Figure 4.5: MR4 TES teacher noise exposure level on the first day of sampling.    123 average of 60 dBA during break/lunch hour (11:28 to 12:28 PM), returning to higher levels of noise during the second class, which reached up to 84 dBA.           On the second day of sampling (from 9:05 AM to 3:26 PM) noise exposure levels in general were similar to the first day (Figure 4.6). They were a little higher during the first three classes (from 9:15 AM to 1:00 PM) than the fourth class. The lowest noise levels were recorded during the break time on that day (1:20 PM to 2:00 PM), when the teacher was in his office in the TES. To give an explanation for the common situations of TES students’ exposures to noise during their time in TES, Figures 4.7 and 4.8 show examples of two students’ results as high and low noise levels from the readings of the noise dosimeter. Figure 4.7 shows an example of a student’s high daily noise exposure level during one metalworking TES (MS3) class. This student was exposed to high noise levels reaching up to 110 dBA while he was inside the welding area and was involved in a lot of hammering. This represented the exposure to impulse noise in TES, which was of an alarming exposure level. His one-hour noise exposure level was 98 dBA. Figure 4.6: MR4 TES teacher noise exposure level on the second day of sampling.    124   Figure 4.7: MS3 TES student noise exposure levels on the first day of sampling.   Figure 4.8: AB1 TES student noise exposure levels on one day of sampling.  On the other hand, Figure 4.8 shows an example of the low noise exposure levels for a student from automotive shop AB1. This student on this sampling day was involved in engine-parts assembly and auto repair, which included using hand tools (e.g., screw drivers, pliers). His    125 noise LAeq ranged from 64 – 88 dBA during the entire hour of the class (from 8:59 AM to 9:53 AM).  4.7.2 Exposure to wood dust in woodworking TES  4.7.2.1 Personal sampling of wood dust for teachers and students Forty-eight wood-dust samples were collected from teachers and students from the same nine woodwork TES in the three school districts.  Table 4.3 shows the results of twenty-two samples for teachers as the daily exposure concentrations and as the averages for 6 hours of sampling. The percentages of time spent by teachers in each woodworking TES are also presented.  Table 4.4 shows that the daily exposure levels to wood dust from twenty-one samples of nine teachers over daily shifts ranged from (< LOD)-3.7 mg/m3 (mean = 1.0 mg/m3, SD = ± 0.9 mg/m3) with averages that ranged from 0.3-2.0 mg/m3 per the number of sampling days. In general, the results in Table 4.5 indicate that the high wood-dust concentrations were found among the teachers who spent longer time of their school-days in woodworking TES and were involved in woodworking tasks.  In addition, Table 4.3 shows that five teachers from WS2, WS1, WS4, WS3 and WS5 were exposed to average wood dust concentrations higher than 1 mg/m3. Teachers from WS2, WS1, WS4, WS3, WS5 and WB1 were exposed to average wood-dust concentrations higher than the action level. However, three teachers in WB2, WR5, and WR6 had averages of daily exposure in compliance with the action level, at which results were ≤ 0.5 mg/m3 for inhalable wood dust.         126  Table 4.3: Teachers inhalable wood dust exposure concentrations in nine woodwork TES. Date TES Time spent in woodwork  % Wood dust concentrations, mg/m3 for 6 hours of sampling/day Per Day Average 28Nov12 WS2 84 0.9 1.0   29Nov12 70 0.6 4Dec12 84 1.4 10Dec12 WS1 33 1.6 1.3   12Dec 33 1.1 13 Dec 40 1.1 11Dec WR5 33 0.5 0.4   7May13 67 0.3 24 Dec 12 WS4 84 1.7 2.0     25 Dec 12 84 0.7 2 May 13 35 3.7 13 March 13 WS3 67 0.2 1.2   6-9 May 13 17 2.2 22April13 WB2 17 0.6 0.3     23April13 17 < LOD* 25 April13 17 < LOD 29 May 13 WR6 80 0.3 0.5   12 June 13 50 0.7 26 Nov WS5 17 1.7 1.7 18 Feb 13 WB1 80 0.4 0.7 19 Feb 13 84 0.9  *LOD (limit of detection) = 0.1 mg/m3 _ substituted with LOD/√2.    Table 4.4: Descriptive results of daily personal exposure to inhalable wood dust in nine TES. Sample type N Concentration of wood dust, mg/m3 Min Max Average SD Teachers 21 (< LOD)* 3.7 1.0 0.9 Students 23 0.3 6.5 2.0 1.7 * LOD (Limit of Detection) = 0.1 mg/m3 _ substituted with LOD/√2      127 Tables 4.5 shows the results of twenty-three wood samples collected from ten students during woodwork class hour. It also shows the daily concentration over each period and their averages per number of sampling days of inhalable wood dust for each student, in mg/m3.     Table 4.4 shows that the daily exposure levels to wood dust from twenty-three student samples over 1-hour ranged from 0.3-6.5 mg/m3 (mean = 2.0 mg/m3, SD = ± 1.7 mg/m3) with averages ranging from 0.4-3.6 mg/m3 per the number of sampling days.   Table 4.5: Students inhalable wood dust exposure levels in nine occupied woodwork TES. Date TES Hours Concentration, mg/m3 Average 28Nov12 WS2 1 0.8 0.9 29Nov12 1 1.7 4Dec12 1 0.3 12Dec WS1 1 0.7 1.8  13 Dec 1 2.9 11Dec WR5 1 0.6 3.6 7May13 1 6.5 7May13 1 3.6 S1 24 Dec 12 WS4  1 3.1 2.8  S1 25 Dec 12  1 5.1 S2 24 Dec 12 1 1.3 S2 25 Dec 12 1 2.9 S2 2 May 13 1 1.8  13 March 13 WS3 1 1.5 3.3 6-9 May 13 1 5.1 22April13 WB2 1 0.4 0.4 23April13 1 0.3 25April13 1 0.6 28 May 13 WR6 1 1.7 1.1 29 May 13 1 0.5 26 Nov 13 WS5 1 0.5 0.5 18 Feb 13 WB1 1 2.9 2.2 19 Feb 13 1 1.5      128 Results of daily average concentrations of wood dust in Table 4.5 indicate that students from all woodwork TES were exposed to concentrations higher than the action limit (0.5 mg/m3), expect student from WB2.  4.7.2.2 Area sampling of wood dust  Table 4.6 shows area wood-dust results for sixteen samples from nine woodwork TES only, because four samples out of twenty were excluded due to bad filter condition or pump operating errors.    Table 4.6: Wood-dust area concentrations in nine woodwork TES. Date TES Measured wood dust concentrations, mg/m3 Per Day Average/#days  28Nov12 WS2 0.7 0.5  29Nov12 0.6 4Dec12 0.2 10Dec12 WS1 0.2 0.2  12Dec12 0.4 13 Dec12 0.1 7May13 WR5 0.6 0.6 24 Dec 12 WS4 1.0 0.7  25 Dec 12 0.5 13 March 13 WS3 0.2 0.2 22April13 WB2 0.2 0.3 23April13 0.6 25April13 0.1 29 May 13 WR6 0.3 0.3 25 Nov 13 WS5 1.3 1.3 19 Feb 13 WB1 0.4 0.4     129 Tables 4.6 shows that area concentrations of wood dust per day for sixteen samples in the nine woodwork TES ranged from 0.1-1.3 mg/m3 (mean= 0.5 mg/m3, SD = ± 0.3 mg/m3). The average per day of sampling ranged from 0.2-1.3 mg/m3. Results for the daily-averaged concentrations show that WS2, WR5, WS4 and WS5 had area wood-dust concentrations ≥ the action limit 0.5 mg/m3. Results of WS4 and WS5 are ≥ TWA 1 mg/m3 However, the rest of the wood TES had wood-dust area concentrations lower than the action level.  4.7.2.3 Specific machine/tool wood-dust concentrations Table 4.7 shows results obtained from the measurements of total wood dust, generated from a number of tools and machines over the entire period of each task.  Total wood dust represents the sum of respirable, PM2.5, PM10 and PM1 concentrations of wood dust directly-detected by the TSI-Dust-Trak 8530.   Table 4.7 shows the measurements recorded for monitored tasks for each selected tool/machine for five minutes.     Table 4.7: Wood-dust concentrations (total dust) generated from specific woodworking tools and machines in woodwork TES. Tool Control status N Period Mean, mg/m3 Min, mg/m3 Max, mg/m3 Orbital Sander Downdraft table 4 5 min 6.0 1.3 16 Band Saw Local extractor 4 5 min 3.3 1.1 11.3 Paper Sanding Not available 5 5 min 1.6 0.2 11 Planer machine Local extractor 3 5 min 1.7 1.1 4.6      130 Results indicate that orbital sanders produced the highest average concentrations of total wood dust (6.0 mg/m3) across the investigated tools. While, the planer machine and the paper sander produced the lowest average concentrations (1.6 and 1.7 mg/m3).  Moreover, results of spearman correlation test for the nine woodwork TES showed that there is a strong negative (r = - 0.7) linear relationship between the size of the TES (room volume, m3) and the measured concentration of wood dust in the woodwork TES, which indicates that wood-dust concentrations are higher in smaller TES (716 – 850 m3). Moreover, there is a positive (r = + 0.6) linear relationship between the type of task and the concentrations of wood-dust exposure, which confirms that teachers or students who are involved in woodwork tasks (e.g. sanding, cutting, etc.) during woodwork classes are exposed to higher concentrations of wood dust than those not involved in these tasks.   4.7.3 Exposure to welding-fume in metalworking and automotive TES  4.7.3.1 Personal sampling of welding fume One teacher and four students were monitored for personal exposure to welding fume in the five selected TES. Sampling was done only during welding tasks in the welding areas, over the entire period of 1 hour of TES class. Results for welding-fume concentrations among one teacher and four students are shown in Table 4.8. The time of welding ranged from 13-43 minutes; samples measured concentrations of welding fume ranged from 0.5-15.2 mg/m3.     131  Results indicate that the teacher in MS1 was exposed to daily and average concentrations of inhalable welding fume higher than the action level (2.5 mg/m3) during sampling. The longest recorded period that students spent in welding was 43 minutes, with an average exposure of 2.3 mg/m3 as found in the metalwork shop MS1. The highest exposure was 7.2 mg/m3 for 26 minutes in the same TES.  However, the lowest exposure of students to welding fume was found in the automotive TES AB1, where the student was exposed to 0.5 mg/m3 over 25 minutes of welding duration. The average concentrations of students’ exposure, ranging from 3.4-5.7 mg/m3 of welding fume was found in three metal shops MS1, MS4 and MR4, which exceeded the action level (2.5 mg/m3).    Table 4.8: Welding-fume personal exposure of one teacher and three students in three occupied metal and one automotive TES (samples collected during welding only). Date TES Welding exposure sampling duration, minutes Welding fume concentrations, mg/m3  Average concentrations, mg/m3 10 Dec 12 MS1 (Teacher) 30 15.2 9.2 12 Dec 12 23 8.0 13 Dec 12 13 4.4 10 Dec 12 MS1 (Student) 26 7.2 4.75 12 Dec 12 43 2.3 13 Nov 13 MS4 (Student) 37 2.0 3.35 26 Nov 13 23 4.7 23 April 13 AB1 (Student) 25 0.5 0.5 10 Oct 13 MR4 (Student) 25 5.7 5.7      132 4.7.3.2 Area sampling of welding fume  Table 4.9 shows the results for welding fume in the air of the welding areas (samples collected inside welding area). Two samples other than the five presented here were excluded, due to filter condition or sampling pump errors.   Area sampling for welding fume durations ranged from 30-60 minutes. The minimum concentration of area welding fume was 1.1 mg/m3 over 30 minutes inside the welding area in AB1; however, the maximum concentration was 9.3 mg/m3 over 40 minutes of welding inside the welding area in MS4.    Table 4.9: Welding-fume area concentrations in three occupied metal and automotive TES.   In general, results indicate that welding-fume concentrations are higher than the action level for welding fume (2.5 mg/m3).       Date TES Welding sampling duration Welding fume concentration, mg/m3  10 Dec 12 MS1 30 1.1 12 Dec 12 60 3.5 22 April 13 AB1 47 3.9 23 April 13 53 2.0 26 Nov 13 MS4 40 9.3    133 4.6.4 Indoor air quality  Carbon dioxide (CO2) was measured in seventeen occupied TES, and results were compared with the standards recommended by ASHRAE (< 1000 ppm) in rooms.  Measuring CO2 is one of the methods to evaluate the efficiency of the dilution (or general) ventilation systems in rooms. Table 4.10 indicates that the averages of the measured CO2 levels in all TES ranged from 635 PPM to 875 PPM, which are lower than the maximum allowable levels (ASHRAE – 1000 ppm) (ASHARE 62.2013). This indicates that the ventilation systems in the TES were working in proper condition for the occupancy on the day of testing.    Table 4.10: Concentrations of CO2 and number of occupants in each TES as compared with standard. TES Occupants # CO2, ppm (averages) TES Occupants # CO2, ppm (averages) WB1 30 875 MS1 28 750 WB2 27 656 MS2 20 780 WR5 25 750 MS3 24 776 WS1 26 750 MR4 20 830 WS2 30 780 WR6 25 826 WS3 24 776 WS5 27 647 WS4 25-30 635 MS4 25 695 AB1 22 660 MB1 20 740 AS1 20 745               134  5 Inclusive Discussion of the Evaluation Results     5.1 Introduction This chapter discusses the results of the evaluation phase of TES from the perspective of industrial hygiene. It discusses the determinants of exposure to noise and airborne hazards, and exposure levels in TES, and the design factors that affect the quality of learning, working and health among teachers and students. Although teachers’ exposure characteristics/factors are different from those of students, the results showed that both teachers’ and students’ exposures exceeded the OEL and/or the action levels in most cases for all hazards.  The results indicated that a number of teachers and students have been exposed to noise levels higher than the action level and higher than the allowable noise exposure limit. Exposure to high levels of noise was related to the type of task and tool, the period of exposure, poor acoustical controls and high background-noise levels in TES.    In addition, participating teachers and students from the woodworking TES were exposed to high concentrations of wood dust. The variability in the results for wood dust was related to a number of factors, such as the exposure period, tasks performed and tools used.  Moreover, exposure to welding fume in metal and automotive TES was found to exceed the action level among the monitored students and teachers. The following paragraphs discuss the    135 findings of the exposure evaluation for noise and airborne hazards in each investigated TES, and factors associated with it.  5.2 Occupational exposure to noise and airborne hazards This section discusses the results of the occupational exposure to noise, wood dust and welding fume in the 17 occupied TES investigated. Hazards control measures status in TES, types of tasks that participants were involved in during sampling, and teachers’ and students’ exposures to noise, wood dust and welding fume, were assessed and are presented in Table 5.1. This section also discusses the determinants of exposure for each measured hazard in the investigated TES during days of sampling.  5.2.1 Exposure to noise Exposure of teachers and students to occupational noise was monitored in 17 occupied TES.  The time of monitoring for each category of participant varied due to differences between learning and working schedules in TES; students learn and work in each TES class for 1 hour, while teachers teach and work in TES classes and at the school for 6 hours. Therefore, students were monitored for their exposure to noise during the TES class hour only, while teachers were monitored for 6 hours, which includes their time in TES classes, and in their offices at school. Monitoring was carried out on 1 to 3 different days of TES classes at each school. In general, results showed that both teachers and students were exposed to higher levels of industrial noise than the adjusted LAeq and the action level (82 dBA), which are also much higher than regular classroom noise levels. However, there was some variation in the results obtained for    136 teachers and students due to factors related to the worksites and the nature of working and learning in TES. These factors of exposure to noise in TES include the room-acoustical conditions, mechanical services noise, the type of TES, the tasks and tools/machines used.   137  Table 5.1: Control measures, tasks and exposure conditions investigated in 17 occupied TES in British Columbia. *   PPE: Personal protection equipment. HPDs: Hearing protection devices.  *  Tasks: S: Sanding; C: Cutting; P: Planer; M: Metalwork (G: Grinding; H: Hammering); W: Welding; Supervision: Teacher was only supervising and assisting TES students; Assembling: Includes working on fixing or joining work parts (e.g., engine). *  Exposures conditions: NS: Noise; AH: Airborne hazard measured related to each TES (wood dust or welding fume); Hi: Concentrations and exposure levels  action limit; Lo:  Concentrations and exposure levels  action limit. *Sometimes: half of the time; Very often: most of the time; Rarely:  not worn when needed.   TES Airborne hazards control Noise control Tasks participants involved in * Exposure conditions* Ventilation Dust collector -condition PPE worn  Source (machines-tools) Path (walls-ceilings) HPDs worn Teachers Students Teacher Student S C P M W S C P M W NS AH NS AH WB1 Yes Yes -Poor Goggles  No No Sometimes*           Hi Hi Hi Hi WB2 Yes Yes - Good Goggles  No No Very often * Supervising      Hi Lo Hi Lo WR5 Yes Not work Goggles  No No Sometimes Supervising      Lo Lo Hi Hi WS1 Yes Yes - Poor Goggles  No Yes - Walls Rarely *           Lo Hi Hi HI WS2 Yes Yes – Poor Goggles  No No Very often           Hi Hi Hi Hi WS3 Yes Yes - Poor Goggles  No Yes - Walls Sometimes           Hi Hi Hi Hi WS4 Yes Yes - Bad Goggles  No Yes -Ceilings Sometimes           Hi Hi Hi Hi AB1 Yes No Goggles  No No Rarely Supervising Assembling  Hi - Lo Lo MS1 Yes Yes – Poor Goggles  No Yes - Walls Sometimes         G  Hi Hi Hi Hi MS2 Yes Yes Goggles  No No Rarely Supervising Assembling   Lo - Lo - MS3 Yes Yes Goggles  No Yes - Walls Sometimes Supervising    H  Lo - Hi - MR4 Yes Yes - Poor Goggles  No No Rarely Supervising Assembling  Lo - Lo Hi WR6 Yes Yes - Bad Goggles  No Yes Sometimes           Hi Hi Hi Hi WS5 Yes Yes – Poor Goggles  No No Sometimes           Hi Hi Hi Hi MS4 Yes Yes - Poor Goggles  No Yes -Ceilings Rarely      Assembling Lo - Hi HI MB1 Yes Yes  Goggles  No No Rarely Supervising Assembling Lo - Lo - AS1 Yes No Goggles  No No Rarely Supervising Parts assembling Hi - Lo -    138 First, TES with poor acoustics had higher noise exposure levels than the properly treated ones. In fact, most of the occupied TES investigated for personal exposure levels of noise are untreated acoustically and had high background-noise levels, as well as high reverberation times. In TES, high background-noise levels were mainly generated from mechanical services available and working properly all the time, such as ventilation systems and dust collectors. These background-noise levels reached up to 82 dBA in unoccupied conditions when no TES machines were in operation, and increased up to 91 dBA in occupied conditions when machines were in operation. This situation was found to be much different from the situation in regular classrooms; previous studies showed that noise levels in occupied classrooms reached up to 77 dBA (Dockrell and Shield, 2006), which is lower than the measured noise levels in TES classes, due to their different settings and the use of dust collectors and machines. High and unacceptable reverberation times in many TES also resulted in high noise-exposure levels, which at the same time made teachers raise their voices up to 80 dBA to cope with the high levels of noise, and communicate. In addition, our observations did not indicate effective noise-control measures exist in all TES. Noisy machines and tools that are used by students and teachers were not controlled acoustically by any means of controlling noise at the source; this situation includes noisy ventilation systems and local dust collectors (Table 5.1). Untreated reflective and hard surfaces in many TES reflected and magnified the noise generated by tools and machines significantly. In other words, untreated walls and ceilings act as multiple reflective surfaces near noise sources (e.g. machines) causing sound reflections which combine with the direct source-emitted noise, resulting in high noise levels (Cheremisinoff, 1996).     139 Second, noise-exposure levels were related to the type of TES and the type of tasks and tools used. Generally, in woodwork and metalwork TES, teachers and students were exposed to very high noise levels.  The highest occupational noise exposure levels ranged from 83 to 91 dBA among four woodwork TES teachers (WB1, WS2, WS3 and WS4), and from 84 to 92 dBA among seven students, four from the same four woodworking TES and three from WB2, WR5, and WS1.  This finding supports Lankford and West (1993) and Dalton et al., (2001), who concluded that teachers in woodwork shops were exposed to very high levels of occupational noise that exceeded the allowable limit of exposure due to a number of factors, including noise-control quality and type of tasks and tools.  It was found that a woodwork teacher from WS2 had noise levels that ranged from 84-100 dBA while involved in woodworking tasks using different tools (e.g., table saw, orbital sander, planer machine, and CNC machine). WB1 teacher was involved in cutting and using a planer machine most of his time working in this TES.  WS3 teacher was supervising and working on cutting using table and arm saws most of his time in the TES.  Teacher from WS4 was sanding using an orbital sander, or spray painting and supervising students working on different tasks associated with noise. Our observations found that all those tasks involved working on tools and machines that are not controlled for noise (Table 5.1).  Students from WS4, WS3, WR6 and WB1 were involved in common tasks that include sanding by router and orbital sanders, and sawing by table saws during sampling days.     140 Students from WS2, WB2 were mostly working on the small planer machine and, for a few minutes, on the arm saw, during sampling days.  Students from WS1 were mostly working on the lathe machine and band saw during sampling days.  Our measurements of tool noise in woodwork TES indicated that these tools generate noise levels reaching up to 100 dBA. Lankford and West (1993) and Pinder (1974) measured tool and machinery noise levels in different high-school woodworking TES and found that noise levels ranged from 85 to 115 dBA; this indicated that exposure to these noise levels in woodworking shops in high schools could be hazardous, especially if the exposure duration is significant. Moreover, dust collectors that were used to reduce wood dust from machines (e.g., planer machine, arm saw, table saw, and lathe machine) were associated with high noise levels as well. Our measurements of the background noise levels when dust collectors were in operation in unoccupied conditions in the woodwork TES mentioned above ranged from 67 to 82 dBA. Also, teachers and students were exposed to noise generated from other machines surrounding them in their TES. In the investigated metalwork TES (MS1, MS2, MS3, MS4, MR4 and MB1), teachers were involved in supervising and assisting students working on grinding, drilling and welding (Table 5.1).  MS1 teacher was involved in welding, besides supervision and assisting 28 students who were involved in different metalwork tasks. The average noise exposure level for this teacher was 84 dBA over the days of sampling.    141 On the contrary, MB1 teacher was mainly supervising and teaching, and was not involved in any metalwork during the days of sampling and the load of work in this TES was low. In other words, types of metalwork in this TES did not include using noisy machines or tools such as grinders. This resulted in low noise exposure levels. Similarly, this was the case among the teachers in MS2, MS3, and MR4. (Appendix F). With regards to students’ exposure to noise, in MS3 a student was exposed to high noise levels that reached up to 100 dBA while using the hammer in the welding area for most of the class time (1-hour). This is a very high noise exposure level that was the result of the impulse noise generated from hammering. (Appendix F). A student from MS1 was involved in two tasks in the days of sampling (welding and grinding) and his average exposure level to noise was 95 dBA.  Generally, previous findings of Dalton et al., (2001) and Mohammadi (2008) support our results, as they found that technicians in small metalwork shops have been exposed to noise exceeding 95 dBA.  Exposure to noise in automotive TES (AS1, AB1) among teachers and students was lower in general than those in woodwork and metalwork TES, but still higher than action limits. The types of tasks they are involved in are car maintenance, arc welding, and engine parts assembling, which did not generate very high noise. However, the measured high noise levels in these automotive shops resulted from ventilation and loud radio music. (Appendix E).   In summary, our investigation results showed that teachers and students are exposed to high levels of noise during their times working in TES classes, especially in woodworking and metalworking TES.     142  Our observations indicated that some noisy tasks (e.g., hammering, grinding, drilling, sanding and cutting) were taking place in the middle of the TES and close to other students who were not involved in any of these tasks. Accordingly, these adjacent students might also be exposed to high levels of noise, since they spend most of the time sitting near these noisy zones; this agrees with findings of Pal Singh et al., (2009). Moreover, a few of the students and their teachers were observed not wearing the required protective equipment (hearing protectors) while doing these noisy tasks, including the students who were not directly involved in, but were within the zone of, these noisy tasks. Lankford and West (1993) results indicated that students enrolled in noisy woodworking/TES classes were at risk to experience TTS as compared to those in quiet classes. Prior to that, Lankford and West (1983) investigated the short-term exposures of students in woodworking shops to high noise levels and their contribution to permanent hearing loss, and found that students were exposed to high noise levels and had higher percentages of sensorineural hearing loss.  The reason for this is that young students are more vulnerable to noise and have more sensitive hearing, which can prove the Equal temporary effect theory that stated that the average noise induced TTS caused by the same daily exposure to noise in the healthy young ear can predict the long-term hazard of a noise induced permanent hearing loss/PTS due to exposure to steady-state noise (Cunnniff, 1976). Moreover, noise induced hearing loss can occur among youth with prolonged exposure to noise levels ≥ 75 dBA (NIH, 2015). In fact, the US Environmental Protection Agency (EPA) long time ago selected 70 dBA as the daily safe exposure level to environmental noise that will protect the average individual from hearing loss over many years (Cunniff, 1977).  The selection of this daily noise level of 70 dBA was based on    143 a correction accounted for a yearly noise dose of 365 days compared to 250 working days (EPA studied the exposure to steady noise over 40 years, and their resulting effect on the population so as to cause a 5 dB noise induced PTS at 4000 Hz; results showed that 96% of the population were protected from hearing damage at 73 dBA ), which then made to adjust from an 8 hour/day  to a 24 hour/day (Cunniff, 1977). Several more recent investigations concluded that NIHL can be experienced after exposure to LAeq higher than 83 dBA. This in fact draws attention that a number of TES teachers could be at risk of developing NIHL from the measured daily noise exposure levels if they are not using the proper hearing protection. Neitzel and his co-authors (2011) estimated the annual exposure level (Leq(8760 hr)) among 4500 individuals in New York city. They estimated the annual exposure to transit noise (users) and other occupational and non-occupational noise sources including MP3 player use, at home and doing other different activities. Their estimation findings according to their collected data concluded that total annual exposure of transit users were higher than 70 dBA, which would put them at higher risk of permanent NIHL than if being exposed to occupational noise alone (Neitzel et al., 2011). This brings to attention the risk of that teacher and students if might being exposed to high levels of noise from sources other than TES during their day.  To predict the annual occupational noise LAeq that a TES teacher might be exposed to in TES, we tried the model that Neitzel et al., (2011) used to estimate the annual occupational exposure of individual workers to noise in New York city. If we use the average Leq(6 hr/day) = 91 dBA of a woodwork TES teacher in the equation-2 used in Neitzel’s study than this particular teacher is exposed to about 84 dBA in a year (estimating that he works for 1560 hours/year out of 8760 hours/year), which is  > the annual limit 70 dBA from occupational source only.     144  Indeed, measurements of noise-exposure levels indicated that many TES teachers and students have been exposed to high levels of noise that are higher than the action limits. The poor acoustics of TES, lack of noise control measures and the use of noisy tools and tasks were associated with exposure to levels of noise higher than the action limits, suggesting the need for suitable control measures in TES to reduce it.   5.2.2 Exposure to wood dust  Exposure to inhalable wood dust was evaluated in nine woodworking TES only, where nine teachers and nine students were monitored for the exposure to wood dust (Table 5.1).  In fact, determinants of exposure conditions to wood dust also include the period of woodwork task/exposure, workload (e.g. students’ number and tasks), the type of woodwork task, and dust-control measures conditions, and the size of TES.  First, averages of teachers daily-exposure concentrations to wood dust were at or above the TWA (1 mg/m3) in five woodwork TES (WS2, WS1, WS4, WS3, WS5), and at or higher than the action limit (0.5 mg/m3) among seven TES teachers (WS2, WS1, WS4, WS3, WS5, WR6, WB1) and seven students (WS1, WR5, WS4, WS3, WR6, WB1, WS2). Students from WS1, WR5, WS4, WS3, WR6 and WB1 were exposed to wood dust concentrations higher than the TWA (1 mg/m3). These results represented exposures of teachers and students who spent their entire time working in these woodworking TES and were involved in a number of woodwork tasks at the same time.     145 Also, our observations indicated that WS2 and WS4, in particular, represent the TES with the highest number of classes and number of students. In these two TES, teachers spent around 80% of their daily shifts there and were involved in multiple woodworking tasks. These two teachers  gave three to four woodwork classes every day, and were responsible for up to 30 students in each class. During these blocks, they had to demonstrate and work on woodwork tasks that generate very high wood-dust concentrations, including wood cutting by table saws and sanding by orbital sander, besides supervising the students working on other machines (Appendix E). Moreover, high personal wood-dust concentrations were also found among teachers who spent short periods in TES, but were involved in woodworking tasks, as a positive, linear relationship was found between being involved in woodwork tasks and exposure to high concentrations of wood dust.  Teachers from WS1 and WS3 worked and taught in these TES for an average of 1-3 hour during the days of sampling, respectively, and were involved in wood cutting as well as supervising groups of students doing sanding and other woodwork tasks. They spent the rest of their daily shift in the office and/or teaching other classes (e.g. electronics or computer classes). A similar situation was observed with the teacher from WB2, WS5 and WR6.  However, the exposures at or lower than the action limits represent teachers who have not been working on dusty woodwork tasks, but were mainly supervising, such as the teachers from WR5 and WB2.  Regarding the students’ exposure to wood dust, the highest concentration of wood dust (6.5 mg/m3) for 1-hour continuous exposure was recorded for a student from WR5 who was    146 involved in sanding using an orbital sander and disc-sanding machine for most of his class time on the second and third day of sampling.  Another student from WS1 spent his entire TES hour working on a lathe machine to shape and sand a wooden mug, and was exposed to up to 2.9 mg/m3 of wood dust.  Measurements of wood dust concentrations from the source indicated and confirmed that cutting and sanding can generate up to 11 and 16 mg/m3 of wood dust in five minutes.  At the center of TES a cloud of wood dust was observed while a number of students were doing manual sanding using sandpaper. Manual sanding using sandpaper is a very common task in all woodwork TES classes, which is always performed by groups of students.  This task generated up to 11 mg/m3 of wood dust, much higher than the OEL and the action level. At least 5 students were involved together in this task, and were at risk of inhaling this amount of wood dust. Moreover, this cloud of wood dust could reach the inhalation zone of other students sitting next to it.   On the contrary, lower personal wood-dust concentrations were found among teachers and students who spent their times in TES, but were not involved in any woodworking tasks. The teachers in WR5 and WB2 spent a short period of the daily shift in the woodworking shop (33-67%) and were not doing any woodwork task associated with high wood-dust exposure.  Student 2 in WS4 was exposed to wood-dust concentrations lower than student 1, as they too were not involved in any woodwork tasks associated with wood-dust exposure.  Thirdly, the volume of the room has an impact on the area concentrations of wood-dust particulates in the air zone of the room. Results of correlation tests showed that TES with small room size have higher concentrations of wood dust than TES with large room size. In large    147 rooms, particulates can have large dispersion areas that could result in lower concentrations of particulates suspended in the air zones of the room, especially if the general ventilation is working efficiently. In all woodwork TES, measurements of the indoor CO2 indicated that the general ventilation was working effectively and providing acceptable concentrations of CO2. For instance, TES with room volumes of 1400 m3 or more (e.g., WB1, WS3, WS1, and WB2) have lower area wood-dust concentrations that ranged from 0.2 to 0.4 mg/m3.  In addition, these findings of low and high wood dust concentrations in the investigated woodwork TES were associated with condition of the equipment and control status available. For instance, observations and measurements of personal wood dust indicated that tools such as orbital sanders that are used in woodwork TES are basics models that are not provided with any dust extraction features. They are neither connected to local or portable dust extractors (e.g., vacuum). Downdraft tables were observed in a number of these woodwork TES (WR5, WS5); but they seemed not to be working very well to control dust while sanding on its surfaces.  As shown in Table 5.1, local dust collectors were installed at machines such as table saw, band saw, planer machines, arm saws and lathe machines in all TES, but were not in proper working order to achieve sufficient dust extraction at the locations where wood-dust concentrations were higher than the exposure limits. Local dust collectors in WR5, WR6 and WS4 were not working or were in bad condition. Although table saws in most of the woodwork TES had local dust-extractor hoods or built-in vacuums to eliminate the emission of wood dust, four of these dust extraction units, in WS3, WS4, WS2 and WR5, were not efficient, resulting in wood-dust concentrations above exposure limits.     148 However, low concentrations of wood dust were observed in woodwork TES with effective ventilation for dilution and effective local dust extractors installed at each machine to eliminate the generated wood dust, as was found in WB2, which is classified as a new and large TES. This finding complies with the findings of a number of researchers (Teschke et al., 1999; Scheeper et al., 1995; Alwis et al., 1999). Students and teachers exposures to wood dust are  0.5 mg/m3 in most woodwork TES. Students who can breathe larger volume of air than the adults can inhale these wood dust particles in higher concentration than the teachers even though they spend shorter hours in TES class. It has been reported that children and young students have increased rate of acute respiratory diseases and asthma due to exposure to fine particulates in high concentrations (Bates, 1995). This would suggest including TES students’ unprotected exposure to inhalable wood dust that is associated with acute health effects to their respiratory system such as nasal irritation.   5.2.3 Exposure to welding fume  In metalwork and automotive TES, teachers and students are exposed to welding fume during all arc-welding (AW) processes. We measured the inhalable particulates of total welding fume through area and personal sampling in four TES (3 metalwork TES and 1 automotive TES) inside welding areas only. Welding areas are the enclosed spaces covered with curtains where teachers and students do welding. Evaluated metalwork and automotive TES conditions of control and exposures to welding fume are presented in Table 5.1.     149  We found that only one teacher and four students in one metalworking and three automotive TES were involved in arc-welding processes such as gas metal and shielded metal. They often spend short times (13-43 minutes) inside welding zones to finish a welding task based on the type of project. In general, the measured area and personal exposure concentrations of welding fume exceeded the action limit (2.5 mg/m3) on most days of sampling in all welding TES.  Exposure factors were related to the variability in the concentration of welding fume, including the period of exposure and the condition of fume control measures.  First, the type of welding and the period of exposure/task were found to be combined factors associated with exposure to welding fume. MS1 teacher’s exposure to welding fume was the highest, and reached 15 mg/m3 in 30 minutes of continuous welding operation on the first day of sampling. This teacher was using SMAW (Shielded Metal Arc Welding), which is known to be one of the arc welding types that generate large amounts of particles/fume (Lehnert et al., 2012). A similar situation occurred for the student from the same TES on the same day of sampling. The student used the same welding technique for about 27 minutes and was exposed to 7.24 mg/m3 of welding fume. The welding area in this TES is a very small, enclosed area made with concrete walls, and the entrance covered with a welding curtain.  Moreover, a measurement for a student from MR4 showed that he was exposed to a high concentration of welding fume during 25 minutes of welding using the same type of welding. (Appendix E). On the contrary, a student from automotive TES AB1 was exposed to the lowest concentration of welding fume during welding for 25 minutes using GMAW (Gas Metal Arc    150 Welding). This student did not spend the entire 25 minutes in continuous welding, but had to leave that welding area frequently to test their work. Moreover, the welding area of this automotive shop is an open area, separated from the rest of the TES by welding curtains on two sides only, and it was served by the TES ventilation system as well.   Secondly, the poor condition of the fume extractor inside the welding area was associated with exposure to high concentrations of welding fume. For example, we observed that the fume extractor inside the MS4 welding zone was not working properly and needed maintenance, as identified by the teacher. This was the main reason for the concentrations of welding fume that reached up to 9.3 mg/m3. On the same day of sampling, student exposure was 4.7 mg/m3, which is also much higher than the action level for welding fume. However, it is lower than the area concentration, and only because this student didn’t remain in the welding area the entire period of his task; he had to test the welded metal piece in another TES (AS1), where there was no exposure to welding fume.  Indeed, these measured welding-fume concentrations were higher than the action level of 2.5 mg/m3. These personal samples were collected from inside the welding helmet (welding mask) without respirator. These measured concentrations of welding fume are inhaled by the teacher and students involved in welding and wearing welding helmets without respirators. Welding helmets without respirators do not provide any respirator protection. In fact, this complex mixture of very small particles (particle size < 1 µm) contains heavy metals and vapors that could be inhaled into the respiratory system and can reach the bloodstream, whereby welders teachers and students could experience different acute and/or chronic health effects (Perkins, 2008).    151  5.3 Summary discussion of synthesis  The findings from this evaluation indicated that a main source of the problems could be associated with the TES environment is the lack of overlap in the mandates of the Ministry of Education and WorkSafeBC governing the learning and working environments within TES, respectively.  Under its jurisdiction, the Ministry of Education builds TES to be industrial workshops and learning spaces.  However, this learning environment is compromised by industrial hazards–in particular, as observed in this study, by the quality of the room acoustics.  Moreover, this evaluation indicated interference in taking and applying the designated responsibilities for the health and safety in TES. Our investigation outcomes suggested that this overlap resulted in that TES environmental and occupational hygiene conditions were not subject for sufficient initial or routine inspection/monitoring as it is with safety issues. The carried out regular inspection by School District Safety and Health Committee/inspectors might be not enough in providing the required elements “for an industrial hygienist” for full inspection of exposures and control measures in TES.  It was observed in this research that the major focus in most of the assigned responsibilities is on safety inspection. Consequently, there was a lack in taking the required action in time to prevent high exposures to noise and airborne hazards in TES, and also prevent any improper protective-behavior among a number of teachers and students.   The following two sections delve into the two issues outlined above by discussing: 1) how the conflicts in TES design and settings have an impact on TES teachers and students; and 2) how the overlap in responsibilities-roles of teaching and working impact health and safety of teachers and students.    152 5.3.1 Impact of the conflicts in TES design/settings on teachers’ and students’ exposures  First, the evaluation of the acoustical conditions in TES involved the investigation of the physical design of shops. This evaluation indicated that TES design is different from that of core learning rooms/classrooms. The construction materials used in TES are like the materials used in basic industrial workshops. The reflective walls in TES are used to stop noise from transmitting to adjacent rooms and to make cleaning easier. However, these reflective walls amplify the levels of noise generated inside the TES, and increase reverberation whereby sound bounces back and forth between the walls.  Also, in TES they use powerful ventilation systems to provide clean air for teachers and students to breath, and local exhaust ventilation to remove pollutants originating in the room (Etheridge and Sandberg, 1996; Awbi, 2003). However, these systems have no noise control measures and generate high levels of background noise that exceed the criteria required for core learning areas. It is important to eliminate and clean the air of wood dust in woodworking TES by using dust collectors/extractors; however, anytime these systems are in operation they emit very high noise levels that can, along with the ventilation systems, reach up to 80 dBA. This is exacerbated by the effect of the reflective surfaces in TES on amplifying this noise, as well as the additional noise generated by teachers and students working with tools and machinery.   In fact, when a workplace hazard like noise is present and is distracting, a greater effort is required to cope with the general situation of supervision, teaching and working; teachers    153 often tend to raise their voices up to more than 80 dBA, or ‘shouting’ level, to be heard by their students in noisy environments like TES. Consequently, teaching or working in situations like this over long periods is associated with adverse physiological and psychological effects among teachers, such as voice problems and job-related stress (Winkworth and Davis, 1997; Messing et al., 1997), in addition to putting them at risk from exposure to high levels of other workplace hazards. Indeed, all these aspects of the design and function of TES are associated with poor quality of learning characteristics.  Second, the evaluation of personal occupational exposures showed that while students and teachers are exposed to unacceptable levels of noise, and are working and learning in acoustically poor environments, they are also exposed to high concentrations of wood dust or welding fume.   Students in woodworking TES are involved in group or individual learning tasks (e.g. sanding, cutting, shaping and carving) that expose them to wood dust and noise in varied concentrations and levels. The current investigation showed that the levels of inhalable wood dust and noise depend on the type of task and tools used, the duration of the task, the use of “effective” dust collectors, and the level of activity inside the TES.   A number of machines and tools in woodworking TES (e.g., orbital sanders, table saw, local exhaust ventilation, extractors) generate high levels of noise and very high concentrations of wood dust.  In addition to noise exposure in metal and automotive shops, students and teachers are also exposed to welding fume while performing welding tasks.  Measurements of inhalable welding-fume concentrations show that teachers and students are exposed to high concentrations of this hazard. This welding fume contains tiny particles of different heavy    154 metals that a teacher or student can inhale in high amounts, especially when they do not use any respirator under the welding mask inside the welding booth. Moreover, students who are not welding, but located close to welders, could be exposed to welding fume, especially since welding-fume particles are not visible, and have the ability to transfer from one location to another if exhaust hoods are not working properly, or if the welding zone is open to the entire TES.  Furthermore, working on welding tasks can also involve exposure to impulse noise; during some welding tasks, hammering is a part of the task.  Hammering on the welded metal piece generates impulse noise levels greater than 90 dBA. Being involved in tasks like this for a period of 30 minutes to 1 hour, and working in another metalworking or automotive tasks for another portion of the TES day, will add up to levels of exposure corresponding exceeding the OEL if that is the case.   5.3.2 Impact of responsibilities-roles of teaching and working on the health and safety of teachers and students. TES were found to represent unique working and learning spaces with complicated conditions of exposure to workplace hazards and safety among teachers and students.  TES teachers work and teach up to 30 students at a time. They are the ones who are directly responsible for the health and safety of all of these students with the cooperation and supervision from the school districts. TES teachers are fully trained for safety in industrial workplaces, however, many of them may not be experienced or trained in occupational health for industrial environments. However, TES teacher may not be able to measure and monitor for    155 personal exposures to occupational hazards. There is a lack in responsibilities with respect to the needed routine monitoring of hazards in TES and inspection for the installed control measures to assure that the provided TES environments are suitable for learning and working effectively without any adverse health problems. The inspection that is carried out by the School District Health and Safety inspector/officer only conducted when a teacher reports an incident of potential hazard or accident happened in the TES. This inspection is mostly related to auditing of the safety procedures in the TES, which are relative to that incident and that should be reported to the committee to take action.  In fact, the handbook “HEADS UP! for Safety” that is provided to TES teachers and their students covers and focuses on the safety issues related to each process and operation in TES. It is mainly emphasizing the required safety procedures that to be followed by the students to prevent injuries, burns and cuts. However, there is a lack in covering the side of industrial health and exposure to hazards. TES students have a little experience in industrial work and a lack in understanding the circumstances of uncontrolled/unprotected exposure to occupational hazards and the associated adverse health in addition to physical injuries and cuts. Moreover, there are no specific exposure limits for students to protect their personal exposure to hazards in TES. This was challenging to decide which are the appropriate OEL for students in this evaluation. It is imperative to develop special exposure limits for youth and students but there might be a number of challenges as discussed in the next section.  Generally, teachers and students in TES were found to be exposed to hazardous noise, wood dust and welding fume because they are using uncontrolled equipment and machines.    156 With regards to exposure to high inhalable wood dust concentrations, teachers and students use different types of wood that could include types of carcinogenic species, but RPEs were never observed  being used in woodwork TES except in one case for the teacher in WS4 who used a half-face respirator during sanding and polishing of a table surface. Few teachers mentioned using the provided half-face respirators only when they are cutting Medium Density Fiberboard. It was not clearly observed that students were wearing the available disposable dust masks during tasks like sanding. They mostly wear goggles and gloves to protect their eyes and hands from splinters. Welding masks have been seen worn by the monitored students and teachers during welding but without respirators in the investigated metal or automotive shops. However, it was learned that in few TES teachers wear the provided half-mask respirators under the welding helmet during welding. Hearing protective devices (e.g., earmuffs, ear plugs) were not seen to be often worn by many students and teachers during noisy tasks (Table 5.1).  It is really challenging for the teacher to insure that all students are following the personal protection plan from workplace hazards as it is his own responsibility to seek for means to encourage his students as stated in TES safety and health handbook.  Consequently, this unprotected exposure indicates that teachers and students in TES are at risk of adverse health effects related to exposure to noise and airborne hazards.     5.4 Challenges of establishing specific exposure limits for students/children Establishing specific exposure limits for children that meet their greater vulnerability would require consideration of many factors and actions. Establishing exposure limits doesn’t involve only the hygienist but also requires the collaboration from different professions related to    157 children’s health such as pediatric environmental medicine. It is crucial to understand and evaluate the factors that affect children’s vulnerability to exposure to hazards in the environment such as high metabolism and respiratory rates, increased surface area to body mass, deficiencies of dietary, hygienic behavior, and the caregivers or supervisors that have direct effect on a child’s safety and exposure. There is a need to understand the mechanism of how a toxic exposure causes disease, which includes the design of an Exposure-Disease-Model for children that addresses and measures the relationship between the contaminant and adverse health effects. The unique toxicokinetics (the absorption and excretion of toxins) and toxicodynamics (the targeted organ of the child’s body: lung, skin) among children would need to be studied. In fact, EPA has recommended an additional safety factor for children (e.g., 10-fold uncertainty factor, a 3.16-fold factor each for toxicokinetics and toxicodynamics variability) (ATSDR, 2012-2016; Dourson et al. 2002; WHO, 2006).  It is crucial to consider the critical windows of exposure/development (age-specific periods of susceptibility). Consequently, this will also help to develop new methods to assess/monitor children’s exposure to hazards and their risks. The assessment methods that are used for adults’ exposures and risks to hazards in the environment do not predict risks to children accurately (ASTDR, 2012-2016; WHO, 2006).  5.5 Summary This investigation of teachers’ and students’ exposures to noise and airborne hazards in Technology Educational Shops in British Columbia showed that poor acoustical quality and the high exposure to these hazards resulted from conflicts arising from having an industrial setting    158 within an educational environment. The Ministry of Education designed and built TES and was responsible to provide the settings in TES to be workplaces for the purpose of learning technical skills in a variety of industries. However, the type of work and activities that TES teachers and students are involved in are all of industrial skills and practices, which include being exposed to different types of hazards due to the materials they use to make products from such as wood. This investigation’s results and observations indicated that the industrial settings were not fully reviewed or assessed from the point of view of industrial health and safety by special officers or hygienists from the School District Health and Safety committees to assure the provision of all necessary requirements for safe and healthy controlled work environment for their occupants, as this research has done. This assessment has found that the industrial control measures provided in TES were in poor condition and resulted in exposure to high levels of hazards. This kind of inspection should be routinely performed, and TES teachers have the right to be informed about the situation so they know how to act toward addressing and applying personal safety procedures in such cases. A TES teacher’s job does not require them to monitor and measure the personal occupational exposure to hazards or test the control systems. In fact, it is supposed to be the school district health and safety committee responsibility.   On a regular basis, it was learned that the assessment of the exposures and the efficiency of control measures in TES is only done when a TES teacher complains about symptoms of illness relative to exposures–that is, when WorkSafeBC or the designated health and safety hygienist   becomes involved.  TES teachers teach their students safety policies and regulations for safe behavior and practice to avoid any physical injury but not involving the occupational hygiene concepts and health effects due to exposure to hazards. However, it was observed that TES    159 students receive and consider these rules as educational information, but not as essential procedures to be practiced properly anytime it is required in TES. It was clear that their main focus is on learning the skills required to do the work (e.g., woodwork, metalwork), even though these skills include essential safety issues. For instance, students and teachers in the investigated TES were observed using personal protection equipment inadequately because they have a lack of knowledge of being exposed to hazards at high exposure levels, which generated from inadequately controlled tools and machines. Indeed, the described findings of high exposure and lacks in providing proper control measures and lacks safety skills among students resulted from the potential conflict that arises from having industrial shops that have not been viewed as industrial spaces with hazards in the context of schools.                 160 6 Acoustics and Airborne Hazard Control in TES   6.1 Introduction Major engineering hazards-control methods in rooms and workplaces include design and retrofit control.  Good design is the first and foremost way to control hazards in any work environment. It requires careful attention to hazard exposure, with respect to the governed criteria and standards for each type of workplace/room, which are mandatory to provide healthy and safe work environments for the occupants. In fact, this upfront design is the most cost-effective methodology to control workers’ exposure to hazards and workplace safety. Room design involves construction materials for the room surfaces, room shape, geometry, and the general ventilation system and equipment.     However, if the workplace design is not providing suitable control quality, it will be necessary to apply retrofit control measures. In general, retrofit control measures for hazards include controls at the source, the path (sound propagation paths between a source and a receiver) and the receiver (e.g., worker). Controls at the source include substitution of the material/equipment, replacement of the source (e.g., process, machine), modification of the mechanical process, or isolating/enclosing the source of the hazard. The controls at the path involve controlling the ventilation/exhaust system, or modification of design elements such as room surfaces and shape, and the layout (e.g., increasing the distance between the source and the receiver). Lastly, control at the receiver includes the provision of PPE and other    161 administrative means (e.g., shift rotations, working remotely) (Malachowski et al., 1999; NIOSH, 2015). According to the exposure evaluation results, TES were found to provide poor acoustical conditions for both intended uses (classrooms and industrial rooms) and high levels of exposure to noise and airborne hazards among teachers and students.    Effective design, and highly effective retrofit control measures, are recommended for these environments.     This chapter discusses the control phase of this thesis framework. It includes three sections: 1) Acoustics and noise control measures; 2) Airborne hazard (wood dust and welding fume) control measures; and 3) Student and teacher behavior control in TES.   6.2 Objective To identify appropriate control measures to make TES healthier places for teachers and students to work and learn. These include acoustical and airborne-hazard control measures.    6.3 Acoustics and noise control measures in TES 6.3.1 General principles of room acoustics and noise control  Room acoustical conditions play a dominant role in the level of acoustical comfort and the quality of communication among the occupants of the room. The acoustical criteria for each room are therefore determined according to the intended purpose of the room.  It is a necessity to consider these criteria at the first stages of room design to avoid any inappropriate    162 acoustical conditions.  These criteria relate specifically to permitted background noise levels (BNL), noise exposure levels (Lex), reverberation times (RTs), and reductions in noise levels with distance doubling (DL2). Determination of acceptable values of any of the standardized acoustical parameters is related to the size and volume of the room, layout, contents, and absorption. In rooms designed for more than one purpose (e.g., in the case of the TES conflict between workshops and classrooms), it is often difficult to compromise between the required acoustical criteria for the two uses (Cunniff, 1977; Smith et al., 1996).  Retrofit control measures for acoustics and noise consider the control at: 1) the sound source, 2) the path, and 3) the receiver.  Moreover, control measures for acoustical quality must be effective at frequencies where acoustical criteria are not met.  The sound source in rooms/workplaces includes the mechanical services (e.g., ventilation and heating systems), powered equipment, tools, machines, and the occupants while they are present in the room, talking, working, learning or being involved in some other activities. Noise control measures at the source include the elimination of the noisy equipment, redesigning of the process, or substitution of the noisy equipment with quiet ones. If the noise cannot be controlled or eliminated by any of these means, engineering controls or maintenance on the machines can be applied. In fact, noise control at the source is considered the most effective method to eliminate noise (Cunniff, 1977; Harris, 1997; Smith et al., 1996; NIOSH, 2014).  If the noise cannot be controlled at the source by any of the mentioned means, alternative engineering controls can be applied to the propagation paths of sound. The propagation paths of sound are the paths through the medium the sound takes to travel from    163 its source to the receiver.  The paths of sound in a room consist of direct versus reverberant sound paths. The sound paths in a room are affected by the interior envelope that contains floors, walls and the ceiling. It also involves the geometry of the room, size, volume, and height. Also, the vibrating body of the equipment and the walls of the ventilation ducts/pipes are considered structure-borne noise path that can be controlled.  Noise control at the paths includes modification of the path components (e.g., installing sound absorption materials on room surfaces to absorb propagating sound, adding barriers and screens between the source and the receiver to block sound propagations, installing mufflers and duct silencers in the ventilation ducts, and building enclosures around the source or receiver), as well as the damping or isolation of machine vibration. Noise control at paths is very efficient to reduce noise to acceptable levels, but it requires careful planning, and the correct installation of noise–control measures (Cunniff, 1977; Harris, 1997; Smith et al., 1996). There is always an interaction between the sound source and the path. Each sound source interacts with the components of the path, in addition to being a noise source.  For instance, in a room with hard, reflective surfaces (e.g., gypsum wallboard, plaster, glass, wood, metal, concrete and ceramic surfaces), sound will reflect or reverberate and possibly even be amplified before it dies out. Rooms with a considerable amount of sound reflective surfaces will also have long reverberation times (RTs) and echoes. On the other hand, if the interior envelope has sound-absorptive surfaces (e.g., porous acoustical ceiling materials, wall coverings, upholstered furniture, carpets and lined draperies/fabrics), sound will be attenuated and the RT will be short, which is preferred for comfort and good communication amongst the receivers that are the occupants of the room. Indeed, perfectly reflective surfaces are considered good sound barriers but poor sound    164 absorbers; however, soft and porous materials are good sound absorbers but poor sound barriers (Harris, 1997).  Sound from sources in a room can also interact with the shape and the size of the room. For example, RT is one of the basic acoustical parameters of rooms and depends primarily on the dimensions and the surface sound absorption coefficient. Therefore, in a large room, sound travels farther between surfaces, resulting in longer RT and echoes (Smith et al., 1996). If the noise cannot be controlled at the source or the path, control measures can be applied to the receiver. The receiver might represent a single person, a classroom of students, or workers in a factory. Control measures at the receiver could include relocating the worker/machine operator, working at remote distance, or providing the workers with hearing protection devices (e.g., ear plugs, earmuffs). This method is the least effective noise control measure (NIOSH, 2015).  Therefore, an important requirement is to first assess the properties of each component (source, paths, receiver) before planning any noise control measure.  For instance, if the goal is to improve the acoustical conditions in a small classroom that is reverberant, it will be effective to reduce RT and noise by applying controls to the paths by installing suitable sound absorbers on its reflective surfaces (e.g., walls or ceilings).  Moreover, efficient sound absorbers are made from materials that convert impinging acoustic energy to some other form of energy — usually heat. However, some products have been developed recently with both barrier and absorbent properties by merging different materials (e.g., a loaded plastic sound barrier bonded to an open-cell foam sound absorber); these are being used in industrial applications, as they are also well suited for quieting noisy    165 equipment and in equipment enclosures used for noisy machines (Smith et al., 1996; Harris, 1997).  As another example, if investigations identified a noisy source (e.g., a machine) in a factory, it will be very effective to reduce that noise by controlling the source. Engineering noise controls that can be applied at the source include the reduction of vibration and mechanical noise by balancing rotating parts, installing isolation dampers, tightening parts or panels, and changing the speed of rotating parts of noisy machines (Smith et al., 1996). Choosing between these methods is based on the condition of the source, and which part of it is most feasible to be controlled.  Source modification is best done by the manufacturer at the design stage.         Furthermore, controlling ventilation noise is especially challenging, because ventilation systems contain some components that participate in generating, amplifying and transmitting ventilation noise (Figure 6.1).   Figure 6.1: Diagram of ventilation system components and features (Smith et al., 1996).    166 Ventilation noise is generated aerodynamically by the motion of the fan blades through the air and is then transmitted via the duct system, and enters the room through the terminal points of the ducts — the grilles (Smith et al., 1996). In addition, fan noise can be transmitted through the duct walls to the workshop and adjacent rooms (duct breakout), and to the outside of the school building.  Structure-borne noise can also be generated by vibrations of the fan casing and motor which are transmitted directly, or through the duct walls, to the building walls, or radiated from the duct. The noise of the air flow is also generated aerodynamically through the duct system; its intensity depends on the velocity of the air and the smoothness of the flow.  In other words, it increases when the air flow rate increases, and is amplified by the presence of any sharp bends.  Figure 6.2 illustrates some of the different transmission paths in ventilation systems.             Figure 6.2: Schematic diagram of fan and duct, demonstrating some of the   noise transmission paths in the building (Smith et al., 1996).    167 The general ventilation noise control measures involve choosing a quieter fan, isolating air handling units (the fans) from the building structure, placing noise absorbing materials inside the ducts (lining), installing duct silencers, and duct lagging to control breakout eliminating any unnecessary bends or sharp angles in the ducting (Smith et al., 1996).  More importantly, after installing any of the noise-control devices, such as a duct silencer, noise enclosure, sound absorbing materials, or sound barriers, it is crucial to measure and assess its efficiency by measuring relevant performance parameters, such as the insertion loss and noise reduction.   Insertion loss (IL) is the difference in noise levels at the receiving point, before and after the installation of the selected noise control device. It is known to be the quantity which is most important to the receiver of the noise. Noise reduction, on the other hand, is a measure of the difference in noise levels across, or on opposite sides of, the noise reduction device.  For example, the noise reduction for an enclosure is the difference in noise levels inside and outside the enclosure (Smith et al., 1996).  These are the general aspects and principles of noise control and room acoustics.  It is important to keep in mind the components of the interior envelope that are related to the design of the room, and how they interact with the sound sources within the room. Furthermore, efficiency, feasibility, and cost-effectiveness are critical factors to be taken into account during the first stages of planning any noise control measure.      168 6.3.2 Suggested noise control measures in TES Results of the acoustical evaluation of TES indicated that TES provide a poor acoustical environment for learning and working that has adverse effects on the quality of teaching for both teachers and students.   This section discusses the proposed methods to control each measured acoustical parameter (BNL, RT, SII, Lex, DL2). Noise control suggestions are to enhance the quality of acoustics in TES to be acceptable environments for working and learning. Discussed control measures cover the three major components of noise control (source, path, and receiver) in the workplace.   6.3.2.1 Controls to reduce BNLs in TES Measured BNLs in TES were much higher than the regulated levels for unoccupied classrooms and occupied learning/working spaces. A number of factors were associated with this finding, including the ventilation noise, noise from dust collectors, equipment, task, the effects of the interior envelope of the TES.  Therefore, to reduce BNL in TES, it is essential to implement some noise control procedures for all or some of these elements as far as possible. Suggestions for acoustic and noise control relate to reduction of noise at the source of propagation, paths and at the receiver. It is imperative that noise levels are reduced, to not interfere with the speech, health and comfort of teachers and students in TES.      169  6.3.2.1.1 Ventilation and dust-collector noise control The primary source of the high BNL in TES is the general ventilation system, which indicated that ventilation systems have never been controlled for noise. Measured BNLs from ventilation systems in unoccupied TES are much higher than the acceptable BNL (35-40 dBA) for unoccupied classrooms that are required for excellent SIQ and comfort. It is highly important to reduce these background noise levels effectively at the source if possible. Engineering control measures at the source that are related to the design and the major components of ventilation systems, include using a quieter fan, slowing down the speed of the airflow inside the pipes by using larger fans which will generate less noise than the smaller, faster fans, but still deliver the same airflow.  Similarly, lowering the air speed in a duct by using larger ducts will also decrease noise levels. These methods are effective in reducing ventilation noise, but it is important to maintain the ventilation airflow rate required to supply the efficient fresh air for the workspace. Therefore, ducts with rounded corners are quieter than ducts with sharp corners, because they provide better airflow around corners, decreasing overall fan noise (Smith et al., 1996). These measures are essentials to control ventilation noise effectively. However, if any of these suggested controls is not easily achievable in TES, it will be important to consider some of the following alternative measures. First an alternative effective noise control measure is to install absorptive duct silencers, which are suitable for use with high volume fans and air handling units often used in schools and industrial shops, such as TES. These silencers can provide attenuation of fan noise; using duct silencers with thin airways, and using thick layers of absorbing materials, can attenuate    170 sound over a broad band of frequencies; however, it is more effective at medium and high frequencies than at low frequencies (Smith et al., 1996, Harris, 1997). Figure 6.3 shows an example of an absorptive duct silencer.  Secondly, acoustical duct–lagging material can be easily wrapped around the ducts and pipes (Figure 6.4 and Figure 6.5). Duct lagging can absorb and control breakout noise, which travels down the duct and breaks through the duct walls into the occupied room.                     Figure 6.3: An illustration of absorptive duct silencer component.  Image source: http://istiqnoisecontrol.trustpass.alibaba.com Figure 6.5: Acoustic duct/pipe lagging and wrap. Image source: http://www.pipeandduct.com/  Figure 6.4: Sound proof duct lagging/wrap material. Image source: http://www.soundcontrolservices.co.uk/    171  Figures 6.6 and 6.7 show suggestions of where to adding lagging materials in examples of two TES with noisy ventilation systems. It is important to select the right lagging materials with the proper insertion loss required to reduce ventilation noise to acceptable levels.              Ventilation ducts  Wrap lagging around all ventilation ducts.  Figure 6.6: Ventilation system pipes in woodworking shop WS3 that can be wrapped with lagging materials to reduce the transmission of ventilation noise to the TES. Figure 6.7: Ventilation system ducts in automotive shop AB1 that can be wrapped with duct lagging materials to reduce the transmission of ventilation noise to the TES.    172 Moreover, dust collectors in TES were found to be generating very loud noise when they are in operation—noise levels reached 80 dBA.  Installing a dust collector exhaust silencer that has acoustic foam between the exhaust of the fan blower and the filter plenum can silence the vibrating air ejected from the fan blower (Figure 6.8). Other ways may include building a sound enclosure around the fan blower outside the building/school, or building a portable sound enclosure with removable walls of absorptive materials around the dust collector that is inside the TES — making it easy to remove when cleaning the filter bags.                  Wrapping lagging materials around the pipes will certainly help to control dust collector noise breaks to the TES (Figure 6.5). Figures 6.9 and 6.10 show suggestions of where to install lagging materials in two examples of woodworking TES with noisy dust collector.   Figure 6.8: A dust collector exhaust silencer and its components.   Image source: http://www.oneida-air.com/inventoryD.asp?item_no=SCOLLECT34     173               Wrap lagging around all dust collector pipes.  Figure 6.9: Dust collector pipes in woodwork shop WB2 that can be wrapped with lagging materials to reduce the transmission of dust collector noise to the TES. Figure 6.10: Dust collector pipes in woodwork shop WR2 that can be wrapped with lagging materials to reduce the transmission of dust collector noise to the TES    174 In woodwork TES, vacuum cleaners are used as small portable dust collectors, connected to the downdraft table to collect dust generated from sanding with the orbital sander. These vacuum cleaners also generate loud noise, which can be attenuated by using portable shop vacuum enclosures (Figure 6.11). These sound-proof enclosures are covered with sound absorptive materials on the inside to absorb vacuum noise, and the outer walls of the enclosure are made of reflective materials.    6.3.2.1.2 Tool and equipment noise control To control and reduce exposure to high noise levels generated by different equipment in TES, it is recommended to eliminate this noise at its source. Whenever feasible, consideration may be Figure 6.11: Shop vacuum enclosure to reduce vacuum noise. Image source: http://www.acousticalsurfaces.com/echo_eliminator/shop_vac.htm     175 given to replacing the current noisy tools and machines – including orbital sanders, grinders, and planer machines — with modern, quiet ones (NIOSH, 2014).  Alternatively, to reduce machine noise (e.g., CNC machines), it may be best to install suitable acoustical enclosures around these noisy machines (Smith et al., 1996).  Moreover, adding vibration damping materials under noisy machines (e.g., planar machine) could be effective to absorb motor vibration and reduce the generated noise from each machine (Cunniff, 1976). Figures 6.12 and 6.13 show where some types of anti-vibration materials can be installed under some machines as an example in two TES.               It may also be wise to implement noise control measures for some of the hand tools that generate very high noise levels (e.g., orbital sanders, grinders, hammers).  These measures include the use of rubber mats under the work that is being held on the workbench or on the Adding vibration damping materials under the machines Figure 6.12: Machines where noise/vibration damping materials should be added to reduce transmitted noise of machine motor in WS3.    176 floor, which can reduce vibration and noise transmission.  The quality and condition of these tools can directly affect the noise levels generated. Replacing the sanding sheets and rubber bases when they are worn or in bad condition will further contribute to prevent vibration transmission and noise reduction.  It is important that students in TES avoid free–running the tool for long periods, as it is indicated that higher noise levels are generated in this condition. Therefore, they should only switch on the tool immediately prior to contacting the work surface (Work Safe WA, 2015).       Adding vibration damping materials under the machines.  Figure 6.13: Machines where noise/vibration damping materials should be added to reduce transmitted noise of machine motor in WB1.    177 6.3.2.1.3 Noise control at the path (interior envelope) The acoustical conditions of the interior envelope of TES need to be improved by installing good sound absorbers on the surfaces of the TES to reduce noise levels.  Suitable sound absorbers for this purpose include porous absorbers (mid and high frequency), and panels of membrane absorbers (low frequency). Porous absorbers are the most common sound absorbers; they allow air to flow into the cellular structure to convert sound energy to heat. Thick porous absorbers can provide better sound absorption or damping at most frequencies. A number of TES are provided with sound absorption panels on the walls, however, they are not absorbing enough noise or at least are not achieving the required BNL. Therefore, materials like mineral-fiber ceiling boards may be installed/added to cover the ceilings in small TES.  In large TES with high ceiling, it is easy and effective to mount acoustical baffles (suspended absorber panels) to the ceilings (Figures 6.14 and 6.15).  This will absorb noise and reduce sound reflections from the hard ceiling of the TES (Smith et al., 1996).   Figure 6.16 shows an example of a TES and how it can have acoustical suspended panels mounted to its ceilings effectively.    In TES with reflective walls, acoustical panels could be mounted to existing surfaces (thin panels can attenuate high frequency noise and thick panels can attenuate low frequency noise). A combined type of panels has thick layers of porous materials covered with a protective cover (Gupta, 2006; Smith et al., 1996).       178                       Figure 6.14: Acoustical ceiling baffles in industrial workshop. Image source: http://www.soundcontrolservices.co.uk/h  Figure 6.15: Acoustical ceiling panels (quiet cloud) in bottle factory.                 Image source: http://info.acoustiblok.com/     179   6.3.2.2 Control to reduce RT in TES Results showed that reverberation times were longer than the criteria recommended for classrooms and industrial workrooms, which concluded that most TES are reverberant rooms.  Surfaces such as walls, ceilings and floors were found to be sound reflectors. Therefore, the need to suggest some feasible means to reduce RT in TES clearly exists.  As was addressed and found earlier, reverberation is affected by room volume, and the amount of sound absorbing materials. Therefore, it is possible to reduce reverberation by the following means:  a) adding effective sound absorbing materials to the walls (e.g., sound absorbing panels) and the ceilings (e.g., acoustical suspended ceiling tiles or baffles) of the TES; or b) reducing the volume of TES by reducing the height of the ceilings, or reducing the length Figure 6.16: Locations suggested to mount acoustical panels to the ceilings of a woodworking TES (WS3) as an additional method to reduce high BNL and RTs.    180 of the room by separating teaching areas from the entire TES.  In fact, installing suspended ceilings tiles can add absorption and reduce room volume by decreasing the height of the room.  6.3.2.3 Control to optimize SII  Poor SIQ was a result of high background noise levels and long RT. Therefore, suggested methods to reduce BNL (e.g., ventilation noise) and RT to acceptable and required values for classrooms can result in good and acceptable SII and excellent SIQ. Moreover, installing sound reflectors above teaching areas can effectively direct the teacher’s voice towards the students.  Another practical method may be using a speech-reinforcement system to amplify the teacher’s voice.  Furthermore, there may be a need for TES teachers to receive the required voice training to enable them to cope with high BNL and avoid vocal strain fatigue (ASA, 2002; Rammage et al., 2003) whenever high BNL exists. Teachers can have clear conversation with small groups of students at short distances (less than 4 meters). A last resort is a suggestion to hold TES class lectures in separated classrooms.   6.3.2.4 Control to optimize DL2 in TES Measurements of DL2 indicated that TES are reverberant rooms and there is a need to increase/optimize DL2 by minimizing room height and installing sound-absorbing materials to walls and ceilings, as well as adding sound screens at a middle distance between machines when applicable.     181 6.3.2.5 Control to reduce exposure to noise (Lex) in TES Teachers and students in TES are exposed to high occupational noise levels during their times inside TES. Reduction of noise exposure is achieved by applying the previously recommended control measures to reduce BNL, such as placing sound barriers between the noise sources and the occupants, installing sound enclosures around noise sources, providing quiet machines and tools.  Moreover, it is required to control noise at the receiver in noisy TES areas, by applying administrative control measures, including reducing exposure times of teachers and students to noise, decreasing the number of students in each TES class to the permitted number, limiting the number of students involved in individual noisy tasks, and providing quiet work areas for times when not working with the noisy equipment or on noisy tasks.  A last resort is providing and wearing suitable and comfortable hearing protection devices (e.g., earplugs or earmuffs) (NIOSH, 2014; Smith et al., 1996).   In summary, if the suggested acoustical control measures succeed to reduce RT, and BNL generated from ventilation systems to the required levels for core learning spaces, TES will be acceptable for use as classrooms for giving introductory lectures to the TES students at the beginning of the classes. For better enhancement, if we also succeed in the reduction of equipment noise levels and the number of students in each TES, it might be possible to use TES for the two purposes at the same time.       182 6.3.3 Hearing conservation program (HCP) for teachers and students  In order to prevent hearing loss among workers, the hearing conservation program was developed.  This program consists of a number of stages/components, including noise measurement, education and training, engineered noise control, hearing protection devices, posting of noise hazard, annual hearing tests, and annual program review (WorkSafeBC, 2016). All these components work together to provide the suitable protection system from hearing loss among workers due to exposure to occupational noise — this includes adult and young workers/employees, which also include TES teachers.  In fact, TES teachers have their hearing tests done annually by independent hearing test professionals in British Columbia as required by WorkSafeBC.   Several studies have shown that the prevalence of Noise-Induced Hearing Loss (NIHL) among school students has increased (Woodford & O'Farrell, 1983; Chermak & Peters-McCarthy, 1991; Montgomery & Fujikawa, 1992).  Therefore, school students who are vulnerable to noise, have the right to be informed about possible risks of hearing loss and trained in how to protect themselves — they should also have their hearing tested routinely (Allonen and Florentine, 1990; Dobie, 1995).  Establishing a HCP for schools was found to be very effective as it improved the knowledge and awareness of the students, as well as prepared them on how to deal appropriately with undue exposure to noise (Knobloch & Broste, 1998; Folmer, 2003). The HCP that is recommended for school students contains the same elements as the workers HCP:  Limit the exposure to excessive noise on school property, screen for NIHL, and    183 teach students how to protect their hearing at school and life in general (NIOSH, 2015).  Implementing a proper hearing conservation program (HCP), is the responsibility of the school district.   Training in the proper hearing personal protection procedures is essential among TES students, as a part of TES “HEADS UP! for safety”.  This includes the importance of knowing when to wear the hearing protection devices and understanding the noise warning signs.  However, this still might not cover all the elements of the recommended HCP for students in TES.  Routine hearing tests, measuring students’ exposure to noise, and education about the harmful effects of noise on hearing are required for an effective HCP.  In addition, hearing tests among TES students who could be exposed to high noise, are mandatory.  Students are young with higher hearing sensitivity than adults, and can develop hearing loss in early stages of exposure to loud noise.  The general recommended/proposed hearing screening of school students, requires that students be tested at least once in high school.  In British Columbia, Vancouver Coastal Health provides outreach services in schools including hearing testing.  Selecting the most appropriate hearing protection devices (HPD) is absolutely crucial, especially for young workers and students.  In fact, there is actually no single HPD that is suitable for everyone.  There are a number of requirements to be considered when selecting the proper HPD, such as personal noise exposure level, individual hearing ability, temperature and climate of workplace, use of other protective devices, communication demands, and the physical constraints of the worker or work activity (WorkSafeBC, 2016).  Complete comfort, fit and proper attenuation of noise are the main requirements that assure the worker would wear    184 the HPD.  However, HPDs should be considered as the last resort against hazardous noise in a workplace when other noise controls are not effective.  It is important to acknowledge that HPDs have a number of problems and limitations.  The major limitations related to the usage of all HPDs types are discomfort, canal irritation, fitting problems, infection, storage and maintenance, inability to hear warning sounds and design limitations (Roysters, 1982).      6.4 Airborne hazard control measures in TES The evaluation phase of occupational exposure to airborne hazards (wood dust and welding fume) in TES revealed the poor air quality conditions in which teachers and students are expected to function optimally — they have been exposed to unacceptable concentrations of these airborne hazards.  Exposure to wood dust can also cause a number of diseases, such as dermatitis, itchy eyes, allergic and non-allergic respiratory effects, sino-nasal effects such as blocked or bleeding nose, and cancer in the nose and elsewhere along the respiratory tract (IARC, 1995).  Chronic exposure to wood dust can cause serious health problems; nasal cancer amongst woodworkers was found to be 1,000 times higher than amongst the general male population (Thrope and Brown, 1994). A number of woodwork processes, such as sanding (e.g., hand paper-sanding, using orbital sanders) and sawing can generate high concentrations of wood dust. Therefore, the optimization of all dust control measures is absolutely essential to minimize the emission of high wood dust concentrations in TES.     185 This section presents the general principles to control/minimize the exposure to airborne hazards, and also describes suitable control measures for wood dust and welding fume in TES.   6.4.1 General principles  Breathing clean air is a basic right of every worker, including those working in industrial workplaces — for this, the air needs to be continuously cleaned.  However, this no simple matter in today's industrial settings, which consist of different types of operations and processes that increasingly use chemicals and hazardous substances.  Using any of these materials is associated with generating and releasing gases, dusts, and vapors into the workroom air in high concentrations that exceed safety limits. The general idea of using effective and well-designed ventilation systems in industrial workplaces is to solve the problems of contaminated air, heat, unpleasant odors, excessive moisture and other uncomfortable environmental conditions (ACGIH, 1995).  In most industrial plants two major types of ventilation systems are being used:  a fresh air supply system and an exhaust system to remove contaminated air and maintain a healthy work environment. A comprehensive ventilation program should always consist of both the supply and the exhaust system.  Supply systems are generally used for two main purposes: to create a comfortable environment in the workplace (HVAC systems), and to replace air exhausted from the workplace (the replacement systems).  These two systems are often in parallel, as in dilution control systems (ACGIH, 1995).      186 Each effective supply system contains an air inlet section, filters, heating and/or cooling equipment, fan(s), ducts, and grilles for distributing the air within the work space. On the other side, exhaust systems are of two types: the general exhaust system (dilution ventilation) and the local exhaust system. General exhaust systems are used for the removal of contamination generated in the work space by flushing it out with large amounts of fresh air. In other words, they are used to dilute contaminated air with uncontaminated air to control the workplace airborne hazards, odors, fire and explosion conditions. However, they are not considered as efficient systems from the hygiene point of view. The effectiveness of these dilution systems is limited: 1) generated airborne hazards should be in low concentrations and uniformly distributed; 2) workers should not be within or near the airborne hazard source point; 3) the toxicity of the airborne hazard generated should be low (ACGIH, 1995; ACGIH, 2007).  Local exhaust systems are the preferred airborne hazard control measure, because they are specifically designed to capture and remove all process emissions before they escape into the work space.  Local exhaust systems consist of four main elements, including the hood to capture and collect contaminants from the generation point in the air stream and direct them to the duct and a duct system to transport this contaminated air towards the air cleaning device (e.g., dust collectors) that removes the contaminant from the air stream.  Finally, the exhaust fan must be big and/or powerful enough to overcome all the losses due to friction, hood entry and fittings in the system, while delivering the planned flow rate, and discharge the cleaned air to the atmosphere via the fan outlet duct (ACGIH, 1995).  There are two types/designs of local exhaust systems: 1) branches hoods over a number of sources/generating points (e.g., machines) located at one end fan and the duct system connected through a long tapered main    187 duct; 2) on-line design: single hood connected to a single air cleaner and single fan at each source (ACGIH, 2007).   When it comes to the health of workers in any industrial workplace, general ventilation systems or dilution ventilation are not as effective as a health hazard control as the localized exhaust systems.  The careful consideration of both systems in an effective way of design and operation is mandatory to provide clean air for the work space.  The performance of the local exhaust system is affected by a number of factors, including the process characteristics, the contaminant characteristics and generation mechanisms, the location of the worker, the airflow rate in the duct, the capture velocity and face velocity at the hood, hood type and the type of dust collectors/filters.  All these factors should be taken into account when a local exhaust system is designed or installed (ACGIH, 1995).    The process characteristics involve the type of raw materials that are being processed, what types of by-products or hazards (e.g., dust, fumes, gases, vapors) may be produced, and how these airborne contaminants are emitted to the surrounding air in the industrial workroom, and in which amounts.  In addition, the behavior of the emitted airborne contaminant also affects the way it will be captured and filtered through the exhaust system.  For example, in woodwork shops hardwood is cut by using a table saw to make wooden chairs.  This type of hardwood may include oak.  When this type of hardwood is sawed, it emits a cloud of very fine particles of wood dust at high velocity due to the high speed of the saw, and in high concentrations over long process durations.  If there is no control procedure to capture these fine particles directly at the source, they will be inhaled by the worker who is operating the    188 machine, and may remain suspended in the air for quite a while.  Moreover, worker position while operating the saw affects the amount of wood dust he/she will be inhaling.  This will determine what type of hood will be required for the exhaust system, where it should be installed with respect to the airflow direction, and what should be the capture velocity to collect the wood dust before it reaches the worker.  Figure 6.17 shows the major types of exhaust hood (enclosed and open/exterior hoods) installations and locations of hoods, regarding the direction of airflow towards the operator’s breathing zone, as used in industrial plants.  Hoods that enclose the process or the contaminant generation point completely or partially as required, are known as enclosed hoods.  These are the preferred type of hoods to be used anywhere the process configuration and operation permit (e.g., laboratory hood, paint spray booth, etc.).  Open or exterior hoods are usually those positioned close to an emission point without enclosing it (e.g., slots along the edge of a tank, rectangular opening on a welding table).  Hoods should always be used in the path of the emission wherever contaminants with large particles are emitted with significant velocity (ACGIH, 2007).    The duct velocity refers to the air velocity through the duct cross-section, which has to be equal to or higher than the minimum air velocity required to move the particles in the air stream, and to prevent settling of the dust in the duct.  The capture velocity is defined as the minimum hood-induced air velocity that is required to capture and convey the contaminants into the hood. Figure 6.18 illustrates how the hood capture velocity is related to the distance from the source.  Furthermore, the face velocity of the hood is the air velocity at the hood opening, which support moving the captured particles to the hood duct. Openings of hoods can be covered with slots — for the slot-type hoods there is slot velocity to take into consideration.     189 It is the air velocity through the openings in the slot-type hood, which is primarily used as a means to obtain uniform air distribution across the face of the hood (ACGIH, 2007). Finally, Figure 6.19 shows an example of the recommended installation of an exhaust system hood for a table saw.  Once the fine particles of wood dust are sucked away into the duct towards the cleaning device (filter), it must be proven that these hazardous particles are filtered completely, collected in the filter bags, and that clean air is released to the atmosphere. This strongly emphasises the careful selection of suitable filters, the capture velocity and the airflow rate (ACGIH, 1995).               Figure 6.17: Major types of exhaust hoods (open and enclosed) and installation locations of exhaust system hoods (ACGIH, 1995; ACGIH, 2007).    190   Figure 6.18: Exhaust system hoods location and capture velocity as  related to the distance from the source (ACGIH, 1995; ACGIH, 2007).     Figure 6.19: Dust collector hood installation location for table saw (ACGIH, 1995).       191 6.4.2 Suggested methods to control exposure to wood dust 6.4.2.1 Engineering control measures  Our observations and measurements showed that high wood dust concentrations were generated from most of the machines and tools used in woodwork TES by students and teachers. Therefore, our suggestions to minimize the concentrations of wood dust include engineering control methods to enhance the wood dust collecting systems in woodwork TES, and applying administrative control procedures to decrease the level of exposure to wood dust.  First, woodwork machines/tools including orbital sanders, table saws, lathe and disc sanders were observed to be poorly controlled in the investigated woodwork TES. These types of machines can generate airflow patterns that make dust control difficult. In fact, it is important to consider to enclose the operation by the exhaust hoods as much as possible. Duct velocity of the hoods used in any of these machines should be maintained at 3500 fpm minimum to prevent settling and subsequent clogging of the duct. Moreover, each machine or equipment type and size has different exhaust flow rates. Table 6.1 presents the different recommended duct velocities and exhaust flow rates for the woodworking machines investigated in TES that generate high concentrations of wood dust. These exhaust flow rates for hoods in this table are based on the well-designed hoods for specific configuration illustrated in industrial ventilation manual of recommended practice of design by ACGIH (ACGIH, 2007). Therefore, configuration evaluation of the shop woodworking equipment is warranted. However, the recommended exhaust flow rates must be increased to accommodate    192 single exhaust ports, smaller connections of the ducts, opening in the equipment base, etc. (ACGIH, 2007).   Table 6.1: Recommended minimum duct velocities and exhaust flow rates for woodworking machines in TES (ACGIH, 2007).    Wood dust from table saws is generally controlled through an exhaust system from the bottom of the table.  This method was found to be ineffective to collect/extract the high generated amounts of table saw wood dust (NIOSH, 1996).  In order to enhance the capacity of wood dust extraction, it is advisable to add a divider plate in the table base and install a local extractor hood over the top of the table (Figure 6.20).  The recommended exhaust flow rates, Equipment/machine Minimum duct velocity fpm Blade diameter, inches Exhaust flow rate, cfm Base Guard Floor table saw 4000 Up to 16 545 350  16 785 350 Dado blade 785 350 Band saw 3500 Up to 2 Bottom  350 Top  350 2 to 3 350 550 3 to 4 550 800 4 to 6 550 1100 6 to 8 550 1400 Belt sanders 3500 Belt width, inches Up to 6 Head end  440 Tail end 350 6 to 9 550 350 9 to 14 800 440 Over 14 1100 550 Jointer 4000 Knife length, inches Up to 6” 350 6 to 12 “ 440 12 to 20 550 20 800 Lathe 4000 -- 880    193 as related to the diameter size of saw blades, are shown in Table 6.1 (NIOSH, 1996, ACGIH, 1995). This method is inexpensive, easy to install, doesn’t interfere with the operator’s task and can reduce wood dust concentration by nearly 90% (NIOSH, 1996).      Figure 6.20: Illustration of auxiliary exhaust hood and divider plate for table saws (NIOSH, 1996).   In woodwork TES, students use hand orbital sanders extensively, and the highest measured concentrations of wood dust were found during this activity. Orbital sanders have a flat base onto which the sandpaper is attached/clamped/fastened. This base has small movements but fast sanding speed (8000-20000 rpm), which results in a low range of wood removal and high finishing quality (Thorpe and Brown, 1994).  Downdraft tables (connected to vacuum cleaner hose) under the work surface were installed in many of the woodwork TES.  It    194 was still fairly obvious that this applied method of wood dust control didn’t extract sufficient orbital sanding wood dust.  An additional suggestion to solve this problem is the use of orbital sanders that have a dust extraction tube connected to a dust collector system or vacuum cleaner (Figure 6.21).  This also includes the installation of a dust control plenum on the orbital sander itself.  A dust control plenum has a series of exhaust slots along its edges, and it actually fits between the sanding pad and the sander unit.  The exhaust connection on the top of the orbital sander pad should connect the plenum with a proper vacuum source (Figure 6.22).  This method can reduce generated wood dust by 90%, it is easy to implement/install, inexpensive to operate and can work with any type of sander (NIOSH, 1996).   Figure 6.21: Orbital hand-sander connected to external wood dust extraction system. Key: A. dust extractor; B. adapter for connection of sander; C. compressed air supply line; D. noise silencer; E. extracted dust tube; F. exhaust air tube; G. flexible hose; H. orbital sander (Thorpe and Brown, 1994).   Hand/manual sanding (using sand paper) is another common sanding task that is performed by a large number of students sitting and working around one big worktable within the teaching area in the TES, which is not controlled by any dust collector.       195  Figure 6.22: Illustration for dust control plenum for orbital sanders (NIOSH, 1996).  As a result, a cloud of high concentration wood dust is formed over this zone.  In order to solve this problem, it is recommended to perform this task within the dust-controlled zones, involve fewer students at a time, and perform these tasks on a special downdraft table connected to a dust collector.   Important installation considerations require that extraction units be positioned in such a way that they do not pull the particulates past the breathing zone of the workers.  To avoid the escape of collected wood dust from the extraction system filter bags, it is recommended to install an enclosure around the filter bag if possible (Thorpe and Brown, 1994).    Saws and sanders generate air flow patterns which make controlling the dust difficult.  Enclosed hoods should be used as much as possible to contain dust emissions from such processes.  Enclosures must be designed for easy cleaning to prevent dust build-up.  Duct velocities have to be maintained at a minimum of 3500 fpm to prevent settling and subsequent clogging of the duct (ACGIH, 1995).     196 6.4.2.2 Administrative control measures and personal protection  Administrative control measures include the routine assessment (inspection by specialists) of the efficiency of the system to extract high emissions of wood dust, routine maintenance of the major components of the system such as filters, fans, and pipes connected to the exhaust hoses of the machines, and regular cleaning of the worksites.  Routine inspection should be conducted to check and assure the efficiency of the applied control measures (ACGIH, 1995; NIOSH, 2015).   Inspectors often find that the correct number and quality Respiratory Protection Equipment (RPE) are available inside many of the TES, but that some of the equipment is not being used.  Goggles/safety glasses and gloves are the only PPE being worn by TES teachers and students during TES, as a safety issue to protect their eyes and skin from wood splinters.   Respiratory protection equipment other than disposable dust masks, should be provided and used by teachers and students whenever there is exposure to wood dust, despite any additional engineering control measures in the TES.  However, it is essential that adequate (correct type for wood dust and can reduce exposure to minimum level required) and suitable (properly fit the wearer, right for the tasks and work environment) RPE be provided to the teachers and students.  To achieve the provision and use of the correct RPE, there are a number of general standardized procedures to adhere to, including the selection of the right type of respirator for wood dust with the correct protection factor; testing for proper fit to wearer’s face to ensure a suitable respirator that fits without air leakage and discomfort is being used; training the wearer when/how to use RPE correctly; supervising the wearer; adhering to the required maintenance and proper storage procedures (HSE, 2014).    197  The personal vulnerability of students to wood dust should be considered to select and provide the proper RPEs (half mask respirators or powered respirators) with the appropriate safe protection factor (HSE, 2013; WorkSafeBC, 2011).  (Additional factors and limitations of using RPEs are addressed in the discussion section).  It is therefore highly recommended that teachers and students wear the fitted and correct type of RPE inside woodwork TES whenever they are involved in woodwork tasks, especially if they are still exposed to hazardous concentrations of wood dust and the engineering wood dust control measures are insufficient.  These RPE of any type would provide personal protection to the wearer only, who must be provided with the right respirators and type of cartridge for wood dust (WorkSafeBC, 2011; HSE, 2013).  6.4.3 Suggested control measures to eliminate exposure to welding fumes This section presents a brief overview of control procedures recommended to minimize the exposure of students and teachers to welding fumes in metal and automotive TES.  To protect them from exposure to high concentrations of welding fumes, it is required to know that the amount of ventilation, and the welder’s proximity to the work, are two important variables that influence exposure.  Most of the observed welding processes took place inside enclosed spaces (welding zones).  Air in these spaces requires highly efficient ventilation and exhaust systems.    A combination of local exhaust ventilation and general dilution is very effective at reducing the amount of welding fume and gases remaining after being generated inside enclosed welding zone.  It is very important to ensure that a local exhaust ventilation system, consisting of a hood, fan, dust and air cleaner, are installed where it can draw away the welding    198 fumes and gases from the welder’s breathing zone (ACGIH, 1995). Enclosing hoods are the option to be highly considered for very effective controlling of welding fume with high hazard condition. However, they restrict access and force reconsideration of material and product handling. Capturing hoods are adequate but for low hazards condition. Capture velocity for these hoods/non-enclosing hoods should be 100-170 fpm with the higher values used for poor conditions such as high cross-draft velocities and with higher hazards levels. Face velocity of enclosing hoods should be 100-130 fpm with the higher values used for poor conditions like cross-draft velocities (ACGIH, 2007).   In case of welding (low toxicity welding) without exhaust hoods, in open area that is moderately blocked by welding curtains and other obstruction to cross-drafts that are not closer than about 7 feet the required airflow of the general dilution should be 1600 acfm lb/hour of the rod used. However, for such welding in open areas where welding fume can easily rise away from the breathing zone the required airflow should be 800 acfm x lb/hour of the rod used. In fact, for this type of low toxicity welding, an option of using portable/movable hoods is suggested. This type of movable hoods can be installed to the exhaust system in the TES in the open area. The benefit of this movable hood that the welder can move it close enough to the welding point to capture more fume particulates. It has to be close enough to the welding point to be effective because it is small and airflows are relatively low. Therefore, it is also required that the minimum design velocity of the exhaust system should be 2500-3000 fpm and the air cleaner in it must be maintained to be effective (ACGIH, 2007).  Moreover, for downdraft benches, the air velocity has to be high, ensuring that fumes and gases generated don’t rise into the breathing zone of the welders. It is also required that    199 the work piece doesn’t cover/ occupy the entire area of the downdraft hood assembly, so as not to lose the effectiveness of the local exhaust.  In addition, the position and posture of the welder’s body relative to the job also influences the risk of exposure.  For instance, if a welder bends over his work while welding pipe racks, his breathing area may be directly above the arc, and that would increase the risk of exposure to higher levels of fumes and gases (ACGIH, 1995).   The measured high concentrations of welding fumes came from the samples collected within the breathing zone from inside the helmet of the students/teachers (Figure 6.23). In fact, even in cases of exposure to low toxicity welding fume the combination of both ventilation and respiratory protection is necessary to ensure that welders are sufficiently protected (ACGIH, 2007).  Therefore, it is a must to provide and use helmets with adequate RPE for welding fume among the teachers and students in metalwork and automotive TES or provide proper RPE such as special welding half-face to be worn under the welding helmets (Figure 6.24).  Again, considerations and requirements regarding RPE type, fitting tests, protection factor discussed in wood dust RPE should be taken into account for welding fume as well. Students’ exposure characteristics and personal vulnerability should be considered as well. As it is difficult to perform fitting tests for all TES students and teachers, it is appropriate to provide powered RPE in welding helmet that could be used by all welders. There are two types for welding fume include the air-purifying masks and the supplied-air respirators.      200                Air-purifying masks can protect the welder from low levels of welding fumes and gases if the correct filter is being used and required frequent replacement for the filter. However, the supplied-air respirators can provide protection from all gases, fumes and vapors, which make them the best choice for protection from welding fume. Proper fit, clear views up, down and sideways, and enough freedom of head movement are very important factors to be taken into account to assure comfort of the welder to keep wearing the RPE whenever welding (WorkSafeBC, 2011; HSE, 2013). To choose the proper respirator, it is important to follow the recommendations/rules of the respiratory protection program of WorkSafeBC (WorkSafeBC, 2011).  Figure 6.23: Student welding in an automotive TES and wearing welding helmet without respirator.    201  In addition, students and teachers who are involved in welding should never stay inside the welding zone without wearing their welding helmets and their respirators.  This is to protect them from exposure to suspended fine particulates of welding fumes in the air inside the welding zones.  Students assisting in welding tasks should also be fully protected.  Furthermore, it is recommended that welding in the middle (open area) of the TES be avoided or limited.  Welding should always be conducted inside special welding booths isolated from the rest of TES.                   Figure 6.24: Welding helmet with built in respirator and filters units. Image source: http://www.zorocanada.com    202  6.5 Student and teacher behavior control in TES Engineering control measures are not the only necessary control measures to be applied in TES to ensure that students and teachers are not exposed to hazards at high levels. There is always a human factor in the workplace that can enhance or worsen the condition of exposure to occupational hazards. This human factor is related to the students’/teachers’ behavior toward the safe work practices (Salvendy, 2001).  Observations indicated that TES students were not corresponding to proper behavior while working on any task related to exposure to hazards. Observations showed that students were not completely aware of the risk from being injured or exposed to high levels of hazards in TES. It was evident that many students have not been using available PPE in proper ways or where they are required. The improper settings of a number of TES equipment and work spaces indicated the deficiency in workplace safety knowledge and experience among a number of teachers.   Practically, to promote protected work behavior to increase prevention of exposure to hazards, it is essential to start with the required training and education before entering TES. It is the TES teacher’s responsibility to influence and apply all needed and creative means to convince students with his knowledge and make sure they learn and understand the workplace hazards and how they can effectively avoid being exposed to them. TES teachers have a major impact on the students’ attitude and behavior toward health and safety, the knowledge they take with them into TES, and the work-related health and safety skills/practices that they begin to develop. This includes the need to motivate the students to practice the elements of workplace safety policy they learned (WorkSafeBC, 2015).     203  It is imperative to correct students’, and some teachers’, conceptions about occupational hazards. They have less concern about the long-term consequences of exposure to hazards; they believe that if they get exposed once or twice to an occupational hazard, this will not affect their health or hurt them, which is wrong. The School District Health and Safety who represent the Ministry of Education and WorkSafeBC in action have to consider supporting and providing resources to promote health and safety awareness toward protecting teachers and students form TES hazards.  A single exposure to some hazards can hurt or kill. The smaller exposures of other hazards can accumulate and lead to increased sensitivity or chronic illness. Moreover, students and young workers believe that occupational disease only happens to elders, which is also wrong. People dying of occupational illness today might have been exposed to harmful dust when they were young (WorkSafeBC, 2015). Students are youth and more sensitive than adults to many hazards due to their personal biological and physiological characteristics, which make them experience illness at early ages.    In addition, teachers’ behavior and practices during TES classes impact students’ attitudes. Therefore, TES teachers must always reflect the proper role model to their students when working and teaching inside the TES.   Effective supervision by the teacher for his/her students should require limiting the number of students in each TES class. Moreover, limiting the number of students in each group doing one task is important to reduce the levels of the hazards generated and eliminate the risk of accidents.     204  Always exclude work habits and acts that unnecessarily increase the risk of injury or illness. It is crucial to make students aware that the TES is a place to work and learn, not a place to play or make pranks, which absolutely can result in workplace injuries and accidents. It is also very important to make it clear to the students to not use/listen to their ipods or other portable devices while working in TES, because this can distract them from other important sounds, such as approaching machinery, alarms or sirens, or warnings from other workers (WorkSafeBC, 2015; Salvendy, 2001).   When working on machinery, it is important to assure that students know and practice the required standard operation procedures. Teachers need to properly use and operate the hazard control systems in place, thus realizing their maximum protective benefits (WorkSafeBC, 2014).  If there is any need to use PPE, it is essential that teachers and students use them in the proper and the required ways to protect them from exposure to high levels of hazards (WorkSafeBC, 2014). Routine inspection and investigations of hazards from different tasks and operations are necessary to assure the quality of the implemented hazard controls. This also emphasizes the importance of reporting and requesting any need for machinery, ventilation or dust collector maintenance in TES (NIOSH, 1996).  Last, but not least, WorkSafeBC has recently updated and developed the students’ 10-12 educational resource package that addresses workplace safety outcomes more widely than in the past, and includes TES classes. It covers what is needed for a variety of instructional settings (whole class, small groups, and independent learning solutions). It gives the chance for critical    205 thinking about workplace safety/protection from exposure to hazards and how to relate these practices to other parts of their daily life (WorkSafeBC, 2015).     6.6 Discussion of control measures and possible conflicts/limitations This discussion is focusing on the possible conflicts between the suggested control measures and addressing the problems and limitations of their implantation in TES.   6.6.1 Possible conflicts between controls procedures (Acoustics controls and airborne hazards controls)  6.6.1.1 Porous sound absorbers vs wood dust in woodwork TES Acoustical panels that are made of porous materials are effective in absorbing sound and reducing reverberation time in broader range of frequencies, especially the fibrous type.  Noise is reduced in the tortuous channels of pores that are present in the porous materials as a result of the viscosity and heat conductivity of the medium.  These porous materials come in three main groups:  cellular, granular, and fibrous porous materials.  Fibrous absorbers are the most effective in attenuating noise over a wide range of frequencies.  In application, sound porous materials are commonly covered with thin perforated sheets (e.g., perforated panels of metal, wood or gypsum), to protect them from damage, to give a pleasant appearance, and to prevent harmful particles from polluting the air (Thakur and Kessler, 2015).  Porous protection panels are not suitable for use in woodwork shops.  The panels may cover a portion of the surface area of the noise absorbing materials. In such dusty workshops    206 the acoustic and sound absorber features of the porous materials may be easily compromised.  The suspended wood dust particles may cover the total surface of the panels and reach the exposed portions of the porous materials through the holes.  Consequently, it may block pores, change the pore morphology and decrease the porosity of the materials that are needed to absorb sound (Lippitz et al, 2014).  Moreover, when there is an excess of wood dust particulates covering the surfaces of the porous materials, it makes cleaning it very difficult.  In fact, this would create another source of dirt that teachers and students may be exposed to in woodwork TES.  An alternative choice for sound absorbers is quilted fiberglass that can absorb noise at a wide range of frequencies and reduce reverberation.  These sound absorbers are unaffected by dirt, dust, and humidity, and have a wide temperature range as well.  They can be easily installed and cleaned.  They are made in different forms such as batts, blankets and boards that can be installed against the walls ceilings of TES (Kineticsnoise, 2009).   6.6.1.2 Ventilation: High speed fans vs. noise levels Ventilation noise that is generated by a fan in operation is a result of turbulence within the fan housing and varies by fan type, flow rate, pressure and fan efficiency.  This fan noise is a type of white noise that is a mixture of all frequencies.  Manufacturers publish sound/noise ratings for their fans.  However, for a fan installed in ventilation system, there is a mixture of surrounding factors that affect the noise level (e.g., interior envelope, components of the room, reflecting surfaces and walls, ducts walls, etc.) (ACGIH, 2007).  One method to decrease fan ventilation noise is to decrease the fan speed sufficiently to muffle the noise but still deliver sufficient air    207 flow to provide the workspace with efficient fresh air, as well as temperature and humidity control (Steemers, 2000).  To wrap the ventilation ducts and pipes with wrapping will also help to reduce the transmission of ventilation noise to TES without affecting the fan speed or the total performance of the ventilation system.  6.6.2 Crucial factors and limitations of installing hoods for exhaust systems  6.6.2.1 Hood design factors Welding activities usually emit large amounts of toxic fumes and gases.  Enclosed hoods are best to contain and capture the emission at the source or the point of welding.  Enclosed hoods have some disadvantages however, including limited access, difficulty to move materials to be welded, difficult to access more than one side of an object to be welded, and some objects may be too large to fit into an enclosed hood.  Installing a rotating platform on the floor of the hood will allow the welder access to all the sides of an object being welded.  Further careful design considerations are recommended.   A moveable hood has the advantage that it gives the welder the opportunity to move the hood close enough to the point of welding to capture as much as possible of the fumes and gases.  The hood “scoop” of most portable hoods is typically small and the airflow is relatively low, but these hoods are still very effective.  However, welders often forget to move or choose not to move the hood close enough to be effective (short capture distance < 12”) — having it    208 further out by an inch or two will reduce its effectiveness considerably.  It is therefore vital to keep the hood close enough to the welding point to extract fumes and gases optimally.  It also happens frequently that welders forget to maintain the air filter on these hoods, decreasing the effectiveness accordingly.  Moreover, moveable hoods are not recommended for confined spaces unless coupled with appropriate use of RPE, because they are not effective with highly hazardous fume components (ACGIH, 2007).  In our situation in TES with teachers and vulnerable students, to maintain the effectiveness of the portable/movable hoods, it is critical that students are trained to know how to move the hood, use it properly to be effective, and maintain it.  In TES where students and teachers often wear welding helmets without RPE, the risk of inhaling hazardous welding fumes and gases exist.  The recommendation is therefore that enclosed hoods be installed and used in all TES welding workshops. 6.6.2.2 Dilution and general ventilation for welding and wood dust Dilution or general ventilation can reduce the concentration of the contaminant by mixing the contaminated air with clean air.  It controls pollutants in the workplace by ventilating the whole worksite.  In industrial settings, dilution or general ventilation should be considered as a complement to local exhaust systems and not as a replacement.  General ventilation is not sufficient to dilute or remove toxic materials and solid particulates such as welding fumes, gases and wood dust.  In fact, general ventilation can spread contaminants throughout the entire workplace and consequently affect workers who are far from the source.   Nevertheless, it may be used without a local exhaust system in very limited situations:  the toxicity level of the contaminant (welding fumes) is low; the periods of operation (e.g.,    209 welding) are very short; the welding activities are interrupted by long periods of other activities, and the activities are being conducted in an open area (ACGIH, 2007).  Therefore, using dilution alone in contaminated working environment including TES by particulates of wood dust or welding fume is not recommended. It is always imperative to use it with local exhaust system. Local exhaust ventilation is the most effective means to reduce and eliminate the exposure to airborne hazards including wood dust and welding fume in high concentrations. However, to achieve the required high efficiency of the local exhaust at each machine it is highly important to maintain the recommended minimum duct velocity, hood face velocity, and flow rates of the exhaust system. For instance, as shown in Table 6.1, to effectively capture and exhaust the generated high concentrations of wood dust from floor table saw it is recommended that duct velocity has to be 4000 fpm minimum. In addition, there is a special minimum exhaust flow rates recommended based on the size “diameter – inch” of the cutting blades. The larger the diameter of the blades the higher the speed of the flow rate recommended at the base and the guard. The point is that with large sawing blade the area of the wood piece being cut is big and the resulting size and amount of dust particulate are larger, which require higher flow rate to capture it and convey it to the duct. The base recommended flow rate should be higher than the guard flow rate, which will help to capture/collect the larger amount of wood dust away from the operator zone or at the guard.           210 6.6.3 Crucial factors and limitations of using HPDs and RPEs   6.6.3.1 Hearing Protection Devices (HPDs) When the provided HPDs in the workplace are correctly selected, fitted, and worn properly, they are intended to provide the workers with effective noise attenuation and protection from noise-induced hearing loss NIHL.  However, if they are not selected and/or worn properly, they may provide negligible noise attenuation, and would be ineffective. It is necessary to select the correct noise reduction rating NRR of HPD that is required to reduce noise under the device reaching the ear canal to optimal protection level of 75 to 80 dBA. It is important to consider the daily noise exposure levels of the teachers and students to find the recommended grade/class of HPDs to reach the protection level. For example, according to WorkSafeBC Class/Grade system teachers whose Lex is 80-89 dBA their recommended HPDs are of grade 1 or class C, and for students with exposures to higher than 95 dBA their recommended HPDs are of grade 3 or class A. However, attenuation much less “overprotection level” than this level will prevent the teacher/students from hearing safety warning and important learning/working information (WorkSafeBC, 2016).  Teachers hearing ability is required to be considered when selecting the HPDs. Workers and teachers with hearing difficulty often refuse to wear HPDs because they feel not safe when they cannot hear warning signals (WorkSafeBC, 2016). Now this type of HPDs with less attenuation are not suitable for workers with sensitive “normal” hearing ability such as TES students and who can develop NIHL at lower noise levels. It might be crucial for students and    211 young workers to select the HPDs with higher attenuation/grade but effectiveness of these HPDs should be tested on them to provide their optimal level of protection.  Hearing protection devices must also be selected and worn in the proper manner to avoid air leaks around the seals of these devices, HPDs material transmission, vibration and flanking via bone conduction, which could all result in passing high noise levels to the ears of the wearers (Le Prell et al., 2011).  Comfort when selecting the proper HPDs is critical.  Choosing the right type and size of HPDs can strongly affect the level of comfort when wearing the HPDs among TES teachers and specially students.  Earmuff HPDs are most often selected because they are more visible from greater distances than ear-plugs HPDs, and they are easy to fit on most wearers.  However, under certain environmental conditions of the workplace, it may not be so comfortable to wear earmuff HPDs.  For example, in hot workplaces or when the work involves vigorous activities, they may become pretty uncomfortable to wear. Furthermore, they can restrict head movement, provide less protection when worn over long hair, cannot be worn with eyeglasses, welding helmet, wood dust mask or RPE.  The headband of the earmuffs can put pressure on the skull and increase discomfort. The cushion materials of the earmuff cannot resist skin oil and perspiration over time and may become stiff or brittle, which will require periodic replacement (Le Prell et al., 2011). These factors can limit the provision or use of earmuffs among TES students and teachers.  Students who wear their hair long or find themselves in workshops with a lot of activity during TES classes, will avoid wearing earmuffs HPDs.  Although earplugs (insert protectors) can be worn and used in any workplace environment condition, can fit with other safety equipment and do not restrict wearer    212 movement, they may require more time and effort for proper fitting than earmuffs. They require special training and experience to be worn and fitted properly to protect against hearing loss.  Moreover, some earplug caps that must be seated snugly in the ear canal, may exert a substantial amount of pressure on the ears, resulting in earplugs often used only briefly or during intermittent noise exposure (Le Prell et al., 2011).   It is therefore essential to always provide a variety of HPDs so that teachers and students may select the equipment that suits them best under the circumstances.  It is also more important for students to wear the proper HPDs, because of their higher sensitivity to noise and to NIHL.  At the same time, it is mandatory to provide HPDs with noise attenuation that does not cover the sounds of alarms and warning signals. In certain tasks such as hammering, TES students can be exposed to very high noise (100 dBA), in this case dual protection (using a combination of earplugs and earmuffs) is recommended (WorkSafeBC, 2011).  In my observation, it was clear that TES students preferred to wear headphones rather than the other hearing protection devices, which in fact can be a source of distraction, higher noise and risk. Therefore, awareness about NIHL and HPDs is highly required to be improved even though students do not spend that long duration in TES as teachers do.  6.6.3.2 Respiratory Protection Program for wood dust and welding fume When selecting the RPE for each activity/task, it is important to choose the equipment with the correct assigned protection factor (APF), which refers to the number on the RPE indicating the effectiveness of the particular RPE.  For example, RPE with an APF of 4 will reduce the teacher’s    213 exposure to wood dust by a factor of 4 if the RPE is used properly, which also means that the teacher will only breathe one-fourth or less of the wood dust concentration present in the air.  An APF can be calculated by dividing the measured concentration by the Permissible Exposure Limit (OEL) of the hazard.  Therefore, if the teacher was exposed to 6 mg/m3 of inhalable wood dust and the OEL used is 1mg/m3, then the APF will be 6.  However, when selecting RPE it is recommended to pick the RPE with an APF above the required protection factor.  In this teacher’s case, RPE with an APF of 10 is recommended.  With regard to the TES students, the situation may be more complicated and critical.  Since TES students are young and therefore more vulnerable to wood dust/welding fume exposure, and their breathing rate is much higher than that of an adult, it may be essential to use an increased protection factor when selecting the correct RPE (WorkSafeBC, 2011; HSE, 2014).  Fit testing of RPE is important to ensure a tight-fitting respiratory mask is face fitted as there must be acceptable contact between the skin and the mask for it to be effective.  Most respiratory protection equipment (RPE) only provides a good seal on the face if the skin or the portion of the skin that is covered by the RPE, is smooth enough to prevent inward air leakage around the edges of the mask.  Therefore, teachers and students with a beard (facial hair) or wearing glasses, will have insufficient sealing between the skin of their faces and their masks, allowing contaminated air (dust and fumes) to leak inward and be inhaled.  RPE fit testing should therefore only be performed by a professional from the supplier (WorkSafeBC, 2011).  Because of the relatively low number of TES teachers compared to all the TES students, doing RPE fit testing on the teachers should not be a problem, and it should be simple   for the school districts under the supervision of WorkSafeBC to manage this effectively.  Conducting proper fit    214 testing of RPE on all woodwork and welding students with such a wide variety of facial patterns and sizes in each high school, will certainly be a challenge and may be expensive.  Therefore, if RPE fit tests prove to be an insurmountable challenge, it may be preferable to provide students and teachers in TES with a selection of powered RPEs that do not require fit tests.  These types of RPEs have a small built-in battery powered motor and fan to blow contaminated air out of the mask/helmet and draw fresh air in through appropriate filters fitted to the mask/helmet.  These powered RPEs provide integrated head, eye and face protection and can work effectively for long hours. It is never recommended to use simple dust masks under any conditions (WorkSafeBC, 2011; HSE, 2013).  TES students and teachers should be adequately educated about the hazards of exposure to wood dust and welding fumes, as well as how to wear and check the RPE correctly, and how to clean, maintain and store them when they are not in use.  6.6.4 Limitations and needs in implementing Hearing Conservation Program on students  A Hearing Conservation Program (HCP) is mandated under the WorkSafe BC, and contains six main components.  Required elements are:  evaluation of noise exposure and noise levels in the work place, audiometric tests, education and training, noise control, hearing protection and program review (WorkSafeBC, 2015). A HCP is required in the workplace when the evaluation of noise levels indicates workers would be exposed to greater than 82 dBA Lex. The implementation of this program for school students in TES would have limitations as outlined below.     215 First, noise exposure measurement and evaluation among students is different than adults because exposure limits that can protect students/youth from noise induced hearing loss have not yet been developed. Therefore, there is a need to establish and develop the correct limits for students taking into account the criteria and factors addressed in the discussion chapter 5. Secondly, hearing tests techniques that are applied to adults cannot necessarily provide accurate results for students. A specialist in health care familiar with hearing testing among youth and children would be required. Moreover, audiometric testing would require an audiometric test chamber to be brought to each school [ANSI/ASA S3.1-1999] (Newton, 2009). Students in schools might need to provide results of the initial hearing tests that they had before entering the schools to use as a base-line test of hearing conditions (normal hearing). However, there is a lack in performing this kind of initial and hearing screening program among school students except as a medical diagnostic test. A suitable solution could be provided by Vancouver Coastal Health - audiology services for children and students’ schools up to 19 years old by request form schools/school districts (VCH, 2015).  Thirdly, available Hearing Protection Devices (HPDs) are designed for adults. Therefore, they don’t provide the best fit for students. For example, the size of commercially available earmuffs is larger than what would be designed for students’ smaller heads to assure full cover/protection over the ears and comfort when wearing.. Moreover, earplugs are designed to fit adults’ larger ear canals. The ear canal resonance depends on the ear canal length, volume, and curvature. Students’ ear canals are smaller than adults, and the smaller the ear canal, the more amplification in the higher frequencies would be (Cowan, 2016).  Therefore, special    216 earplugs that fit students’ smaller ear canals would need to be developed. The correct noise attenuation for children/students is not the same for adults for a similar noise exposure. It is crucial to select and provide the correct attenuation for an HPD and avoid overprotection which would have the unintended consequence of blocking other sounds such as warning signals. Fourth, there are limitations regarding adequate hearing conservation education and training program for youth/students. The available material and content that provide information about the danger of noise hearing loss are not interactive, simple and cautionary enough to have students’ attention and positive response in practice. However, an interactive educational program about NIHL has recently been developed by WorkSafeBC as a video clip for students and even adults. More importantly, the training should include the evaluation of the students/young workers practice toward taking the recommended steps/procedures to protect themselves from the danger of noise and hearing loss (Folmer, 2002).  Finally, even though noise control at the source and at the path is the most effective way to reduce noise generated in the workplace, it is still not taken seriously by the employers/principals (school boards) due to cost and necessity of correct application of the noise reduction measures. Applying engineering noise control considering exposure of students is more difficult because it requires more reduction of noise generated taking into account the high sensitivity of hearing and hearing loss among youth, and the lack in providing the safe exposure levels.    217  6.7 Summary  Investigated TES were found to provide poor acoustical conditions in industrial workrooms and classrooms.  Moreover, TES teachers and students were found to be exposed to unacceptable levels of noise and unhealthy concentrations of wood dust and welding fumes.   The need for suitable and effective control measures for acoustics, noise and airborne hazards is evident. Suggested control measures involve engineering modifications, administrative measures and personal protection recommendations to reduce exposure to noise, wood dust and welding fumes for all of TES.  Suitable/applicable engineering control measures to reduce noise levels from the source in TES include installing absorptive duct silencers inside ventilation ducts; wrapping the pipes and ducts of the ventilation and dust collectors with acoustic lapping; reducing tool noise (e.g., orbital sanders) by using rubber mats under the objects/work being held on the workbench; reducing machine noise by installing noise/vibration damping materials underneath the machines (e.g., planer machine); replacing noisy hand tools (e.g., sanders, grinders) with new quieter ones. To enhance the acoustical condition and promote the quality of working and learning, it was important to suggest a number of control measures to reduce reverberation times, DL2 and noise levels.  These suggested measures could be applied to the design components (interior envelope-path) of the TES.  For example, install better sound absorbers (e.g., quilted fibreglass panels) to the walls and/or mount them on the ceilings of the TES; reduce the room volume of the TES by reducing the height of the ceilings; separate teaching areas away from noisy work areas.     218   Administrative methods included a number of procedures.  First, decrease the number of students in each TES to the permitted limit to reduce general noise due to presence of students.  In addition, to protect TES teachers and students from induced hearing loss, it is required to provide the correctly fitted hearing protection devices and assure wearing them properly by teachers and students.  The most applicable control measures to reduce exposure to wood dust included engineering modifications on the machines that generate high concentrations of wood dust, such as to improve the capacity of wood dust extraction on the saw table by installing a divider plate in the table base and adding a local extractor hood over the top of the table; eliminate orbital sanders dust by providing orbital sanders that have a dust extraction tube connected to a dust collector system or vacuum cleaner; hand sanding should be performed on a special downdraft table connected to a dust collector, enclosed hoods have to be installed to contain dust emissions from woodworking machines. For more individual protection and when engineering control measures do not provide the efficient reduction of hazardous wood dust, it is recommended that teachers and students wear the fitted and the right type of powered respiratory protection devices inside woodwork TES whenever they are involved in woodwork tasks.   In order to reduce exposure to welding fumes inside the welding area, a combined ventilation system of local exhaust ventilation and general dilution ventilation will be very effective. Furthermore, increasing the air velocity of the downdraft benches could prevent fumes and gases from rising toward the breathing zone of the welders.  For effective personal protection from inhaling hazardous welding fumes, it is highly recommended that TES teachers    219 and students TES be provided with welding helmets and adequate powered respirators for welding fumes.  Last but not least, education and training about exposure to noise and airborne hazards and their associated adverse health effects in the long run, should be improved especially among students.    Indeed, for TES to be adequate places for technical skills learning for students in high schools and even students from other trades, TES has to provide the sufficient and promised quality for learning and working in healthy and safe environments. To achieve this target, there is a number of procedures to be taken seriously in improving the quality of TES. First, the acoustical quality of TES has to be enhanced to be accepted for teaching and learning effectively. Second, exposure to noise and airborne hazard has to be controlled to minimum limited exposures to provide the optimum protective environment for teachers and students. Moreover, to complete all these procedures the assigned responsibilities for School District health and safety Committee, inspectors/officers and teachers have to be evaluated, improved and addressed explicitly. It should be including the responsibility to perform the sufficient initial (for new TES) and routine occupational hygiene inspection, exposure monitoring and control measures. Immediate actions and positive responses should be always conducted in time, reported and evaluated. Teachers have to be motivated and encouraged to manage the required healthy and safety condition in their TES. Finally, students’ susceptibility to exposures and their personal characteristics-behavior must be always kept in mind to provide the optimum health condition for them.     220 7 Conclusion    7.1 Overview This chapter re-examines the empirical findings that achieved this dissertation’s objectives, and discusses the contribution, strengths, limitations and the implications of the research. It concludes with considerations for possible future directions for this work.   7.2 Objectives and key empirical findings  The objectives of this dissertation were: (1) to investigate the acoustical conflict in TES environments resulting from the two uses of TES, as an industrial workshop and as a classroom; (2) to evaluate the exposures of teachers and students to noise and airborne hazards (wood dust and welding fume) in TES; (3) to suggest suitable control measures to make TES healthier places for teachers and students to work and learn.   In summary, we found that TES failed to provide the required environmental (design-setting) conditions to meet existing acoustical regulations for industrial workshops and classrooms at the same time and, therefore that an acoustical conflict exists in TES. TES students and teachers are exposed to noise, wood dust, and welding fume at levels and concentrations higher than prevailing action limits and OEL during learning and working in TES. Factors associated with the exposure to these higher levels include the type of tasks and tools, the time of exposure to the hazards, and the poor condition of the control measures provided    221 in the investigated TES. Additionally, these findings indicated the need to propose suitable retrofit control measures to provide healthy and safe work and learning environments for both teachers and students.    7.3 Scientific contributions The goal of this dissertation was the evaluation and control of occupational exposure to hazards among teachers and students in Technology Educational Shops in high-schools. The foundation of this evaluation was based on the principles of occupational and environmental hygiene, which employs the principles of recognition, evaluation and control of hazards to provide protection for health and the environment. During the evaluation phase of the worksite, necessary information about the worksite under investigation were collected, which were followed by a qualitative walkthrough-survey to get the ‘big picture’ about the characteristics of the worksite and the hazards. After gathering all relevant information, an assessment of exposure was done by measuring the hazard and its components.  The next stage examined the results of the evaluation and recommended feasible control measures to eliminate or reduce the exposure to the workplace hazard. In this particular work, the research included evaluation of additional components related to the unique working and learning environments that were investigated. It included the evaluation of the design and settings of TES, and examined the possible acoustical conflicts that could exist due to having two different purposes for the same place, and the conflict in occupational exposure to hazards that also could arise from using an industrial design for educational environments. The following sections illustrate the key phases    222 of this comprehensive evaluation as contributions to the existing level of knowledge in this area.   7.3.1 Evaluation of the acoustical conditions and Conflicts in TES (Chapter 3) We found that TES had unacceptable/high background noise levels, reverberation times, speech intelligibility quality, and DL2 when unoccupied/occupied. This study was the first of its kind in measuring and evaluating these acoustical characteristics together in TES in high schools.  The measured background noise levels and reverberation times in the investigated TES were higher than the maximum permissible criteria for unoccupied core learning spaces (classrooms) and industrial workshops. The increased levels of background noise were associated with several major significant factors related to the settings and design of TES, which included noisy ventilation and dust collectors, and untreated walls. High ceilings, large room volume, hard and reflective surfaces in TES were the most significant factors for the increased reverberation times. These findings support previous studies conducted in unoccupied classrooms and learning spaces (Pekkarinen, and Viljancn, 1991; Hodgson et al., 1999; Celik and Karabiber, 2000). In addition, background noise levels in occupied TES were much higher than in unoccupied TES for the same design factors, in addition to machine/tool noise and activities. Similar findings were reported by a number of researchers in occupied classrooms (Hodgson et al, 1999; Shield and Dockrell, 2003; Picard and Bradley, 2001), and in industrial workrooms (Cunniff, 1977).     223 Our findings regarding the reduction of sound levels with distance doubling in TES as industrial workrooms indicated that many of the investigated TES were considered as reverberant rooms. This confirmed the fact that the design and settings of TES, with large size and reflective surfaces, work together as significant determinants that provide unacceptable acoustical characteristics for both purposes as technical workshops for working and classrooms for learning.   This indicated the unique design of TES, as they are different from the design and settings of regular classrooms in schools. Consequently, the speech intelligibility quality required for good verbal communication between teachers and students was unacceptable in the occupied TES.  Teachers had to raise their voices to ‘loud’ or ‘shout’ voice levels to be heard by their students, due to the high BNL and RT that masked and interfered with their voice levels.  This, in fact, was found to result in poor verbal communication quality. Previous studies (Losso et al., 2004; Kristiansen et al., 2013; Hodgson, 2004) in classrooms supported this finding with respect to high background noise levels and reverberation times. However, no studies have been found that investigated this characteristic in TES or other small industrial workshops. Finally, these findings concluded that TES failed to provide acceptable acoustical conditions for both uses as classrooms and as industrial workshops. An acoustical conflict exists.  7.3.2 Occupational exposure to noise and airborne hazards in TES (Chapter 4) We found that teachers and students in TES are exposed to high levels of TES noise, and high concentrations of wood dust and welding fume, that exceeded the daily the action limits and    224 PEL during their time working and learning in TES (in woodwork, metalwork and automotive TES). The most common significant determinants for these high exposures were: (1) type of machines and tools used; (2) task type; (3) exposure duration; (4) hazard control measure condition; and (5) the number of students and the workloads in TES. In fact, this research was the first work investigating conditions of exposure to workplace hazards among teachers and students, and addressing the gaps/conflicts resulting in creating poor and precarious situations of working and learning in TES. Our woodwork teachers and students were found to be exposed to high noise levels and high inhalable wood dust concentrations when they were involved in tasks like sanding using orbital sanders, or cutting using table saws for most of their time in a busy TES that has ineffective noise and dust control measures. In addition, our measurements in metalwork TES showed that teachers and students who were involved in welding, hammering and grinding were at risk of being exposed to impulse noise and high concentrations of inhalable welding fume.  The previous few studies in TES investigated teachers’ exposure to wood dust in woodwork TES and exposure to noise in metalwork and automotive TES also confirmed that teachers have been exposed to higher levels of noise and higher concentrations of wood dust (Pinder, 1974; Lankford and West, 1993; Ahman et al., 1996; Meding et al., 1996). However, it was not obvious if there were other studies conducted among TES students. This study is the first study focused on teachers’ and students’ exposure to hazards and the different factors associated with their exposures in TES.    225  The measured high and unacceptable exposures led to the conclusion that control measures that are provided are not in proper condition to reduce or eliminate exposure to hazards (noise, wood dust and welding fume). There is a lack of routine inspection of control measure conditions, equipment conditions, and workplace hazards.   Indeed, designs of many TES in British Columbia did not provide all requirements for safe and healthy working and learning environments.  7.3.3 Acoustics and occupational hazard controls in TES (Chapter 6) Our evaluation of acoustical conditions and the exposure to hazards in TES showed that TES could not provide the adequate environmental design or efficient control measures required to achieve the intended healthy and safe working and learning environments for teachers and students in high schools. Therefore, there is a need to propose suitable retrofit control measures to enhance the acoustical quality of TES and to reduce the levels of noise, wood dust and welding fume to permissible exposure levels.  Taking into account the vulnerability of students to exposure to hazards. Recommended control measures in TES followed the hierarchy of control illustrated in Chapter 1 and Figure 1.6. The suggested control measures involved a number of engineering procedures that include modifications and maintenance of the equipment and tools used, and ventilation and dust collection systems installed to reduce noise, wood dust and welding fume. These control measures also include installing sound absorbing materials on the walls and the ceilings of TES to reduce background noise levels and reverberation times.     226 Moreover, administrative measures have to be applied to the teachers and students, including proper training and proper use of personal protection equipment.   To our knowledge, this was the first study that investigated the settings and control measures in TES and recommended several suitable means to optimize their design and control measure conditions, in an attempt to make them healthier and safer working and learning environments in schools.    7.4 Limitations and strengths 7.4.1 Limitations in conducting exposure evaluation of teachers and students in school TES A) Obtaining approvals and recruiting participants (Chapter 2) The evaluation of exposure to noise and airborne hazards in this study required carrying out personal sampling of real exposures among teachers and students in high-school TES. This required meeting with teachers and students in person, and attaching a number of monitoring devices to them to measure their exposures while working in TES. To reach this point, and to conduct occupational and environmental hygiene studies on human subjects, we had to obtain ethical approval from the University of British Columbia, and obtain approvals to conduct research in schools from the school districts in Richmond, Surrey, and Burnaby. It took about 4 to 5 months to get approvals from Burnaby, Richmond, and Surrey, but we were not able to obtain approval from the school board in Vancouver, as they withdrew from participation for some unknown reasons.     227 Our target sample size was 24 TES, 24 teachers and 24 students from the three types of selected TES. After getting the school districts’ approvals (Richmond, Burnaby, Surrey) we had to seek approval from each school that has one or more of the TES types with teachers interested in participation. It was hard to contact the schools to arrange the time for meetings with TES teachers. We contacted many high schools in the three cities; the majority of them refused to participate. Even though we had some teachers who expressed interest in participating during the pre-visits, they changed their minds when asked to sign the consent forms. In the end, we had only 17 teachers from 17 different TES, including the three types of TES (woodwork, metalwork and automotive). To complete this step, we spent four more months, which involved meetings with the teachers, explaining the procedures of sampling, and parts of the consent forms, and recruiting students. This is why we had the opportunity to measure exposures in only 17 occupied TES.   B) Difficulties during sampling and field measurements We were not able to do sampling for three days as planned for all of the participants for a number of reasons, including job actions and discontinuing employment or participating of some teachers. During these strikes, we could not do any sampling/measurement because all schools were closed for months. Consequently, some participating teachers discontinued involvement in the study, or left or moved from their schools to another; this was an obstacle to continuing sampling the same teachers or even entering the same schools again to recruit new teachers. Accordingly, this reduced the number of area and personal samples we collected for the three hazards dramatically.     228 Furthermore, some samples of noise and airborne hazards could not be collected or analyzed successfully due to sampling instrument failure, including air sampling pump problems, and noise dosimeter errors. These instruments often stopped during measurement, even though they were fully charged. The flow rate of these pumps dropped dramatically or fluctuated during sampling time. Therefore, we could not succeed to obtain the measured samples using these devices, which led us to exclude these measurements and repeat them on other days (as applicable) using other devices. Because of the complicated sampling situations in TES, this did not work for all samples.  C) Evaluation of the exposure results  There were limited, or no, studies which evaluated the designs of small industrial shops or TES and their effects on acoustical conditions. Furthermore, there were limited sources of knowledge in the field of the study – that is, exposure to noise and airborne hazards among students and teachers in TES.  It has been challenging to evaluate students’ hazard exposure levels according to the regulated maximum allowable exposure levels that apply to adult workers in workplaces. Studies reported that young workers or students are more vulnerable to hazards than adults due to their personal biological characteristics (e.g., higher breathing rates, larger and more sensitive skin absorption portion), which always raises a question as to whether the available standards are more dangerous for young workers or students than adults. Published literature could not actually provide an answer to this question, or even tested the available exposure limits on youth. Therefore, in this study, there was one possible way to judge our findings of exposures among students, and even teacher: by comparing them with the minimum allowable    229 limits that are the action levels, as they are the limits at or above which the workers are at risk and control measures are relevant to be applied to reduce the exposure to workplace hazards.   There was a limitation in the type of the data collected that could be relevant to exposures in TES, which results in limited number of exposure determinants that could have been analyzed and tested for further correlations.   D) Date statistical analysis  The data were examined for significance using a Student’s t-test, or ANOVA as appropriate.  There were no significant findings by the t-test due to the small sample size (n). Future research in this area should involve a larger sample size in order to meet the assumptions of the t-distribution.                                                                              7.4.2 Strengths Our literature search indicated a lack of information about the working and learning environments of TES, and about young workers’ exposure to hazards in TES and small industrial shops. In fact, no studies were conducted or published in Canada or British Columbia investigating any of these aspects. Moreover, we found none that investigated the quality of hazard control measures in these working and learning environment. This was the first study which filled the gap in the existing knowledge about acoustical conditions and conflicts in learning environments and small industrial workshops.  We explored and examined the existence of this acoustical conflict in this interesting learning/working environment, and evaluated all relevant room acoustic parameters. Also, we studied the design and settings of TES and how they affected the quality of acoustics for learning and working.    230 We were the first researchers studying and filling the gaps in knowledge about the conditions of occupational exposure to noise and airborne hazards among young workers like TES students in high schools. This study explored and evaluated the factors and determinants associated with the exposures.  This study completed the application of the industrial hygiene paradigm by the evaluation and recommendation of control measures to reduce the exposure to noise, wood dust and welding fume, and enhance the quality of learning and working in TES by making it healthier and safer for occupant students and teachers.  More importantly, this dissertation has fundamentally provided insights into the conflicts that exist between using TES as an industrial workshop for work, and as a classroom for teachers to teach and for students to learn, and the conflicts that exist between teachers’ and students’ exposures and the occupational health regulations of industrial settings in the educational environment.  This research provided insights and information regarding students and young workers’ behavior and safe work practices in industrial workspaces. Our investigation also suggested a lack in applying the proper safe work practices/protective behavior among students in TES, as they are not sufficiently aware of the workplace risks and how to be more serious about being protected from them.  This study brings the attention toward the required actions and procedures for supervision and monitoring student behavior, and exposures to hazards and routine assessment of the environmental quality of TES.  There is a need for the Ministry of Education as the School District Health and Safety Committee and WorkSafeBC to work together on this,    231 taking into account the recommended steps to control and improve the instructional guide by including the criteria and guidelines for protected exposure to hazards to avoid any adverse health effects due to prolonged exposure other than the physical injuries and accidents.    7.5 Research implications The findings of this dissertation have implications for exposure evaluation methodology among students and teachers, and for potential acoustical control and exposure reduction approaches, as described in the following sections.   7.5.1 Exposure evaluation methods for students and teachers in schools Based on the outcomes of this study, we offered several recommendations for conducting exposure evaluation among students and teachers in TES.  This study, in the exposure evaluation and monitoring, used direct observation to identify the determinants of exposure among students and teachers during their time in TES. This helped in getting an understanding about the worksite factors and participants’ behavior that have an influence on the measured exposure levels. It would be more practical in further investigations to employ the use of an observation checklist that cover all possible determinants, and information about the workplace, to avoid missing any of the determinant information during sampling, which would also provide a more consistent data collection.  Collecting enough technical information and data about the control measures available in TES, and their effectiveness will strongly support the research in designing or recommending    232 the most suitable control measures, or alternative procedures, to enhance the indoor environmental quality of TES.  Collecting data about the monitored tasks other than the type of task, tool, location and its duration, would help beneficially in understanding more about the elements related to exposure conditions and the control requirements. This information could include the type of materials used, the position of the student while doing that task, and the type of protective equipment required and worn during that task, and its condition.   7.5.2 Acoustical controls and exposure reduction  This dissertation has identified areas where control measures could be applied or evaluated to reduce exposure to noise and airborne hazards in the investigated TES, as discussed in Chapter 3 and 4.  It can be indicated that the industrial environment of TES did not receive full inspection or assessment by experts as industrial hygienists during the phase of design, and the operating phase. This type of inspection was fundamentally needed, especially in complicated working and learning environments like TES, to assure providing the required elements in the design and settings for healthy and safe working/learning conditions for teachers and students.  In fact, the investigation of acoustics and exposures in Chapters 3 and 4 filled this gap, and identified the potential settings of TES and exposure determinants among students and teachers in TES that include TES design and construction materials, the condition of the control measures, and the type of tasks and tools.      233 Therefore, implementation of several preventative, administrative, and control measures is essential and feasible in a number of ways:  - Required acoustical control measures have to be applied to the design components of the TES (e.g., adding sound-absorbing panels on the walls or ceiling, reducing the size of the TES) to provide acceptable background noise levels and reverberation times to obtain excellent verbal communication quality and comfort. - Inspections of tools/machines noise (e.g., orbital sanders) showed the need to apply noise control at the source (e.g., substitution with quieter tools, engineering modifications by adding damping materials under planer machines).  - Applying engineering modifications to machines and tools that generate high concentrations of wood dust, such as orbital sanders and table saws.  - It is required to train TES students in the proper behavior and work practices needed, and to assess their understanding and ability to adopt these safe-work policies during working and learning in TES. This should include two skills: the first is workplace safety skills and the second is the skill needed to operate machines and tools. Students must fully understand that a TES is an industrial workshop that has many hazards that they could be exposed to and must behave appropriately.  - It is important to provide, and test the use of, personal protection equipment (PPE) among the students, and assess their comfort level.  - It is hard for a TES teacher to supervise and take care of 30 students working at the same time, and assure their protection from being exposed to loud noise or high inhaled wood    234 dust. The number of students in TES should be decreased and be limited to TES teacher limit of supervision.  -  Routine investigation of the air quality and noise levels in TES should be carried out by a hygienist from WorkSafeBC in TES; results must be delivered to the principals and TES teachers to act toward addressing and applying the required control and safety procedures. - Routine and further technical testing of ventilation systems’ and the dust extractors’ operational condition and quality. Further modifications and maintenance must be applied to any of these two systems’ components as required, and testing after modification should take place.  7.5.3 Stakeholders who should be at the table in relation to actions that arise from the study In order to properly construct a TES with adequate engineering controls, the following professionals would need to be included at the design stage:  British Columbia Technology Education Association (BCTEA)  British Columbia Teachers’ Federation   WorkSafeBC  Ministry of Education in British Columbia  School Districts Health and Safety co-ordinators  Acoustics and noise specialists    235  Physicians/Specialists in Pediatric Environmental Health and Medicine   Industrial hygienists   Architects/Building Engineers  7.6 Future directions These dissertation findings raised several questions and identified a number of areas where future studies could be focused in the same field. These ideas are described below.   7.6.1 Noise and acoustical characteristics and performance/health studies There are no studies that evaluated the acoustical conflicts and conditions in small industrial workshops and TES before this study. Therefore, it would be valuable to add more evidence to the existing knowledge regarding this area.  There is a need to conduct more studies about noise levels and room acoustical quality in TES.  Moreover, this type of future studies could involve the subjective evaluation of the productivity, comfort and learning quality among teachers and students as associated with the acoustical conditions in TES.  Exposure to hazards and biological monitoring studies could be effective, and a comprehensive way to evaluate physiological and psychological health effects associated with exposure to noise in TES among students and teachers in schools.  This also could include the evaluation of noise induced hearing loss by applying auditory tests among students and teachers.     236 7.6.2 Exposure to wood dust and welding fume and health effect studies  Given the very limited numbers of published studies about exposure to wood dust and welding fume among young workers, students and teachers, more and deeper studies should be conducted. Future work about students’ and young workers’ exposure to hazards in different workplaces is needed, to focus on the characteristics of these hazards and exposure patterns.  In this study, we focused on measuring and evaluating the general exposure to inhalable wood dust and welding fume, but we did not include further chemical/metal analysis of the components of the collected samples for these two hazards. This additional part of future work would provide more details about the types and the concentrations of the heavy metals and chemicals that students and teachers are exposed to, and draw a picture of the level of risk they are at and how to prevent it.  Also, it is important to develop a preformed field sampling sheet with a list of determinants, conditions of sampling and exposure, to decrease the likelihood of missing an exposure factor. For example, recording the type of metals (e.g., coating, work piece) used in each welding task would give an idea of the types of welding fume components the participants might be exposed to and inhale, and similarly with wood dust evaluation.  In addition, future studies in this area could investigate the health effects associated with exposure to these evaluated hazards. It would be possible in future work to include biological monitoring studies of the health effects among young workers and students in TES or in small industrial workshops.     237 Future studies about exposure in TES could involve the evaluation of hazards other than the ones investigated in this dissertation. These studies could monitor exposure of teacher and students to solvents, metal particulates, heat, and cold. Future intervention studies that focus on evaluating the quality of training programs provided for youth entering employment sector would help in improving the level of safe work practices, personal protection and productivity.   7.6.3 Control measures, safety policies and safe work practice evaluation studies From this study we found that one of the major factors that influenced exposure levels and poor working and learning environments in TES is the poor condition of control measures available in them.  Our findings of exposures, and our observations, concluded that control measures in TES either need to be installed or improved.  Future studies could perform measurements of ventilation and dust collector air flow rate, fan speed and duct sizes. In fact, this would add valuable technical information describing the efficiency of these installed control measures in TES, to technically support the relevant control recommendations.   In addition, it was noticeable that there was a lack in practice of safety requirements among teachers and students in TES. Therefore, studies focusing on evaluating the safety guidelines in TES/small shops, and work safe behavior among young workers and students, will be necessary to give indications about ways to motivate and enhance student’s personal behavior in the workplace and how to use PPE properly when needed.  Motivation and support    238 from School Districts Health and Safety Committee as it is responsible for students’ health and safety, should be considered to conduct these studies. Since it was challenging to decide which exposure limits to use in our evaluation of students’ exposure to hazards in TES, future studies should seriously concentrate on the assessment of the recently developed limit of exposures that apply to adults and to youth. These studies should come up with a plan to establish exposure limits for youth, considering their personal characteristics, vulnerability to hazards, and their level of understanding of the risks of exposure to hazards in the workplace.  There is a need to develop, or at least address, the safe exposure levels that ensure exposure without any adverse health effects.    7.7 Conclusion This dissertation is a comprehensive pilot study that filled the gaps in the existing knowledge of teachers’ and students’ exposure to hazards in TES. 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Hearing Protection Devices. Retrieved January, 20, 2016 from: https://www2.worksafebc.com/pdfs/hearing/criteria_hearing_protection_selection.pdf WHO. (2015). Hazard Prevention and Control in the Work Environment: Airborne Dust. World Health Organization. Retrieved September, 12, 2015, from http://www.who.int/occupational_health/publications/en/oehairbornedust3.pdf    257 Woodford, C., & O'Farrell, M. L. (1983). High-Frequency Loss of Hearing in Secondary School Students and Investigation of Possible Etiologic Factors. Language, Speech, and Hearing Services in Schools, 14(1), 22-28.  APPENDIX A         Old woodwork TES with hardwood floor.       Metalwork TES – large size – and has sound absorption panels on the walls.    258  Students  in a large automotive TES.     Large metalwork TES with high ceilings, concrete floor, and reflective walls and ceilings.+ A section for classroom with low ceiling.     259  Students in a woodwork TES – working on simple woodwork tasks.      Teaching area in a metalwork TES has low acoustical ceiling.             260 APPENDIX B          261 APPENDIX C                      262     263                                     264       265      266      267      268      269               270 APPENDIX D   Sampling sheet         271 APPENDIX E                                                          Sampling pump and filter are attached to a student in a woodwork TES. Three students are doing sanding using sanding papers.    272       Woodwork teacher is sanding by router sander, and wearing respirator.                      Woodwork students are assembling a frame stand.    273                                            A woodwork student during wood cutting by electrical saw at the rear open storage. Woodwork student working on jointer machine.    274    Two students doing arc welding in a metalwork TES. This welding area is not confined, and located within the metal shopand covered with curtains from three sides.     275  Measuring noise during hammering in metalwork TES.    Students working on a car in an automotive TES.    276 APPENDIX F           277        278        279  APPENDIX G      280       281   

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