Influence of atmospheric fine particulate matter (PM 2.5 ) pollution on indoor environment during winter in Beijing

The objective of this study was to investigate the influence of atmospheric fine particulate matter (PM2.5) pollution on indoor environment. Time series of indoor and outdoor PM2.5 mass concentrations in a naturally ventilated building were monitored continuously and simultaneously in winter in Beijing when haze-fog episodes happen frequently. Relationships between indoor and outdoor PM2.5 mass concentrations were examined and discussed. Indoor and outdoor PM2.5 mass concentrations showed close correlation (R2 = 0.9104) when the windows are closed and there are no obvious indoor particle sources. The peak values of average indoor PM2.5 mass concentrations appeared at night, which were 1.5 times higher than the minimum values in daytime and showed an increasing trend from Monday to Friday in workdays. The indoor/outdoor PM2.5 mass concentrations ratios (I/O ratios) are closely correlated with outdoor wind speed and relative humidity. A prediction model was developed based on a method of mathematical statistics and it was applied to estimation of indoor PM2.5 mass concentrations by using outdoor PM2.5 mass concentrations and meteorological parameters as inputs. There is a good agreement between model results and the measured values with correlation coefficients of R2 = 0.95. The findings can provide meaningful reference to further research on influence of atmospheric PM2.5 on indoor environment and help further develop approaches to control outdoor originated indoor PM2.5 in the haze-fog episodes.