Influence of natural ventilation rate on indoor PM2.5 deposition

Particle deposition can significantly affect occupants' exposure to PM2.5 in indoor environments. However, there is a lack of experimental data for the PM2.5 deposition rate under different ventilation rates in naturally ventilated rooms. This work experimentally examined the influence of natural ventilation rate on PM2.5 deposition in two university classrooms in Nanjing, China. The results showed that the deposition rate was linearly associated with the natural ventilation rate for both classrooms. An empirical equation was developed to correlate the PM2.5 deposition velocity with the natural ventilation rate. The developed empirical equation was then applied in three scenarios to illustrate the influence of natural-ventilation-rate-dependent PM2.5 deposition velocity on the infiltration factor, I/O ratio, and air cleaner selections. The analysis showed that the PM2.5 infiltration factor and I/O ratio were less sensitive to the natural ventilation rate when the influence of natural ventilation rate on deposition velocity was considered, compared with a constant deposition velocity. The required clean air delivery rate (CADR) for the air cleaner might be underestimated if the influence of natural ventilation rate on deposition velocity was not considered. Therefore, the dependence of PM2.5 deposition velocity on natural ventilation rate should be considered in PM2.5 infiltration factor calculation, I/O ratio prediction, and air cleaner selection.