%0 Journal Article
%A William J Riley
%A Thomas E McKone
%A Alvin C.K Lai
%A William W Nazaroff
%B Environmental Science & Technology
%D 2002
%G eng
%P 200-207
%R 10.1021/es010723y
%T Indoor particulate matter of outdoor origin: importance of size-dependent removal mechanisms
%V 36
%X <p>Adverse human health effects have been observed to correlate with levels of outdoor particulate matter  (PM), even though most human exposure to PM of outdoor origin occurs indoors. In this study, we apply a  model and empirical data to explore the indoor PM levels of outdoor origin for two major building types:  offices and residences. Typical ventilation rates for each building type are obtained from the literature.  Published data are combined with theoretical analyses to develop representative particle penetration  coefficients, deposition loss rates, and ventilation-system filter efficiencies for a broad particle size range  (i.e., 0.001-10 um). We apply archetypal outdoor number, surface area, and mass PM size distributions for  both urban and rural airsheds. We also use data on mass-weighted size distributions for specific chemical  constituents of PM: sulfate and elemental carbon. Predictions of the size-resolved indoor proportion of  outdoor particles (IPOP) for various conditions and ambient particle distributions are then computed. The  IPOP depends strongly on the ambient particle size distribution, building type and operational parameters,  and PM metric. We conclude that an accurate determination of exposure to particles of ambient origin  requires explicit consideration of how removal processes in buildings vary with particle size.</p>