Penetration of Particles into Buildings and Associated Physical Factors. part I:Model Development and Computer Simulations

摘要

The PM_(2.5) standard proposed by the U.S. EnvironmentalProtection Agency (EPA) has stimulated research on the relationshq between particulate matter concentrations and the exposures an subsequent health responses of sensitive subpopulations, such I the elderly. Since individuals in these subpopulations may spen more than 90% of their time indoors, understanding the relatiol ship between outdoor particle concentrations and those found j indoor microenvironments is critical. This research resulted in time-dependent indoor air quality model incorporating all potel tial particle sources and loss mechanisms. Monte Carlo simul; tions of the model identified the mechanisms, such as particle 101 during penetration through the building envelope, that modify tl1 outdoor particle size distribution during transport into the interi< of a building, calculated indoor-to-outdoor (I/O) concentration rl tios, and estimated penetration factors as a function of particl size. Indoor particle generation and transport of outdoor particll through the HV AC system were the most important contributors 1 the indoor concentration in residential and commercial building respectively. The most significant removal mechanisms include ventilation through and particle removal by the HVAC filter if a HV AC system was present, or particle deposition on indoor surfacl if an HV AC system was not present. The modeled I/O concentratio ratios varied between 0.05 and 0.5, depending on particle size an type of ventilation system, and agreed well with published exper mental results. Penetration factors less than unity were calculate for particles with aerodynamic diameters larger than 0.2 #mu#m if tl1 air exchange rate and steady-state I/O concentration ratio were COI related during the simulations. An additional correlation betwee the air exchange rate and particle deposition velocity is required penetration factors less than unity are to be modeled for particll with aerodvnamic diameters smaller than 0.2 um. These resull support the possibility that appropriate experimental studies will yield penetration factors less than unity.