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UBC Theses and Dissertations

Infiltration of forest fire and residential wood smoke : an intervention study to asssess [sic] air cleaner effectiveness Barn, Prabjit


Forest fires and residential wood-burning are significant sources of fine particle (PM2.5) air pollution. As PM2.5 exposure is associated with adverse health effects, populations need to be provided with exposure reduction strategies during smoke episodes that are practical, effective, and evidence-based. Public health recommendations typically include remaining indoors and use of air cleaners, yet little information is available on the effectiveness of these measures. Specific objectives of this study were to measure indoor infiltration of outdoor P M2.5 from forest fires/residential wood smoke, to determine effectiveness of High Efficiency Particulate Air (HEPA) filter air cleaners in reducing indoor PM2.5 and to investigate determinants of infiltration and air cleaner effectiveness in homes. Winter sampling at 21 homes was conducted in 2004 in a northern Canadian community affected by residential wood-burning. Summer (2004-5) sampling at 17 homes was conducted in southern British Columbian communities impacted by vegetation fire smoke. Indoor and outdoor 1-minute PM2.5 averages and a 48-hour outdoor PM2.5 filter sample were collected at each home. A portable HEPA filter air cleaner was operated indoors with the filter removed for one of two sampling days. Infiltration (Finf) was calculated for each home using a recursive model (Switzer & Ott, 1992; Allen et al., 2003). Housing characteristics data were used in multivariable modeling of infiltration and air cleaner efficiency (ACE). Valid samples were obtained from 19 homes in winter and 13 homes in summer. Mean Finf ± SD values of 0.27 ±0.18 and 0.61 ± 0.27 were found for winter and summer respectively, for days when the filter was removed, with lower values of 0.10 ± 0.08 and 0.19 ± 0.20 on corresponding days with filters in place. Mean ± SD ACE, calculated as [Finf without filter - Finf with filter]/ Finf without filter, in winter and summer were 55 ± 38% and 65 ± 35% respectively. Infiltration was predicted by the number of windows in a home and the season (p<0.001) while no significant predictors of ACE were identified. Remaining indoors combined with air cleaner use was concluded to effectively reduce PM2.5 exposure during forest fire and residential wood burning episodes.

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