Fate of particles released by a puff–dispersion with different air distributions

Well-mixed assumption normally has flaws in the space with continuous-releasing particle sources. For transient point or puff sources, however, particle concentration might vary differently among locations during emission periods and afterwards. This study measures whether and how rapidly ventilation systems can distribute particles emitted from puff-like sources in an indoor space. The impact of ventilation pattern (over-head mixing ventilation and displacement ventilation), particle size (0.77, 2.5 and 7 μm) and source location are also examined. The results show that particles with sizes of 0.77 μm and 2.5 μm can be distributed uniformly by both mixing ventilation and displace ventilation shortly (within a few minutes) after particle injection is terminated, regardless of particle source locations with the absence of obstructed airflow. This paper validates the well-mixed assumption when assessing long-term human exposure to puff-generated particles in the indoor environment. With regard to puff sources, the spatial concentration enhancement in human microenvironment/breathing zone might not be as significant as continuous-releasing particle sources.