Transport process of outdoor particulate matter into naturally ventilated buildings

Natural ventilation of buildings can bring in fresh air, remove indoor air contaminants, and improve indoor thermal comfort. However, ventilation may also bring outdoor pollutants and/or aerosol into the buildings to affect the indoor air quality. This study uses a computational fluid dynamics model and a Lagrangian particle tracking model to investigate the transport process of outdoor particulate matter (PM) into a naturally ventilated building. The simulation results indicate that the entrance rate of outdoor PM contaminants is in the range of 7%–25%, depending on the particle size and the distance between the pollutant source and the building. The indoor concentration of PM_2.5 decreases as the external wind speed and ventilation rate increase. In other words, sufficient natural ventilation can remove indoor particulate contaminants. In addition, the deposition rates in long buildings are larger than that in short buildings, owing to the sluggish airflow inside the long buildings. This study also estimates the time scales of particle deposition and ventilation-induced advection. The results reveal that the ventilation-induced airflow dominates the removal of fine particles PM₁ and PM_2.5, whereas the ventilation and deposition are equally important for coarse particle PM₁₀.