Infiltration of fine particles in urban buildings

Singapore is a tropical country that can be affected by outdoor fine particle air pollution. Little information is available on the penetration of outdoor fine particles into daycare environments. Our study attempted to address the following objectives: to measure indoor infiltration factor (Finf of PM2.5 from outdoor fine particles and to determine the building parameters that modifies the indoor PM2.5. We collected indoor/outdoor 1-min PM2.5. from 50 daycare environments. We noted high indoor and outdoor concentrations of fine particles due to the presence of regional haze pollution. Indoor and outdoor fine particle concentrations are significantly highest for daycares located near highways while indoor to outdoor ratios were significantly lower for air-conditioning use in daycares. Mean Finf±SD of 0.65±0.19 in daycare rooms which are naturally ventilated and lower Finf±SD values of 0.46±0.22 for those that are air-conditioned. The penetration coefficients and air exchange rates were higher in naturally ventilated daycares (0.78 vs 0.61 and 1.47 vs 0.86 h−1 respectively). Our findings show that children remaining indoor in daycares where air conditioning is used can reduce PM2.5 exposures during outdoor pollution episodes.