Particle deposition and decay in a chamber and the implications to exposure assessment

Accurate modeling indoor aerosol deposition and decay is an important step for exposure assessment. High deposition rate reduces indoor pollutant concentration and results in lower inhalation exposure. Many of indoor surfaces have random roughness protrusion scales up to several millimeters which it may significantly affect the deposition loss rate. Aerosols deposition onto most indoor surfaces can be considered as "rough' surface deposition. However, particle deposition from anleaflong indoor environment is frequently modeled by assuming that surfaces are smooth. In this work, experimental results for deposition velocity onto drywall surfaces for supermicron particles from 1 to 7 mu m are presented. Deposition velocity is significantly higher than that predicted by a previous published model. To illustrative the influence of particle deposition on exposure, two hypothetical room sizes and two air exchange rates were considered. Inhalation transfer factor was adopted as a risk exposure index. Taking into account of high deposition velocity onto drywall surfaces, inhalation transfer factors are 8 to 35% lower than that predicted by the model and this significant difference is important to the exposure assessment.