Modeling the Ratio of Indoor to Outdoor Particle Exposures in Commercial Buildings

The exposure of building occupants to outdoor particles is a potential concern for health risks. The goal of this project is to characterize indoor exposures to particles of outdoor origin inside commercial buildings. Steady state simulations, using code written in the Python programming language, were used to capture the exposure of building occupants to outdoor particles and to examine the exposure variability across examples of the commercial building stock. Model input distributions were determined from a literature review of the parameters expected to affect indoor particle exposures. The building exposure ratio was calculated for 108 scenarios involving combinations of building type, particle size, filter rating, and meteorological conditions (as they affect building operations). Results showed that on average, commercial buildings provide 90% protection from outside particles. Specifically, it was determined that occupants in schools on average have lower building exposure ratios (~2%) than do those in office and retail buildings (~7-12%). In addition, the variability within building classes decreases with larger particle sizes and the exposure ratios are higher for smaller particles. Differences in meteorological conditions do not significantly affect BER calculations.