Relationships of indoor/outdoor inhalable and respirable particles in domestic environments.

Simultaneous air monitoring inside and outside of three domestic environments in residential and industrial communities were conducted to evaluate infiltrations of outdoor aerosols into indoor environments, and indoor aerosol characteristics. The relationships of total (TSP), inhalable (< 10 microns, PM10) and respirable (< 2.5 microns, PM2.5) suspended particles were compared. It was found that the fractions of the indoor (20%) and outdoor (40%) PM10 levels exceeding 150 micrograms/m3 were substantial. In addition, it was indicated that indoor TSP and PM10 concentrations (R2 = 0.99) were well correlated with their corresponding outdoor levels. Moreover, there was a close relationship between the paired PM10 and PM2.5 levels indoors (R2 = 0.75) and outdoors (R2 = 0.83). The average indoor/outdoor (I/O) and median I/O ratios observed were 0.60. Therefore, steps to mitigate the situations with particulate levels above ambient particulate standards requires further study.