Analysis of occupants’ exposure risk of cough-expelled droplets in the workspace with various mixing ventilation layouts

This study numerically investigated the transport characteristics of the cough-expelled droplets and their corresponding exposure risk of each occupant under various mixing ventilation layouts. Transient simulations were conducted in a conference room, while pathogen-bearing droplets were released by a standing speaker. The results showed that droplet residues (< 40 µm) had a high potential to reach occupant’s breathing zone, among which the number fraction of aerosol residues (< 10 µm) could be nearly doubled compared with that of the rest droplet residues in the breathing zone. Occupants’ exposure risks were found very sensitive to the ventilation layouts. The strong ventilated flow could significantly promote droplet dispersions when those inlets were closely located to the infectious speaker, resulting in all occupants exposed to a considerable fraction of aerosols and droplets within a given exposure time of 300 s. The mixing ventilation layout did not have a consistent performance on restricting the pathogen spread and controlling the occupant’s exposure risk in an enclosed workspace. Its performance could be highly sensitive to the location of the infectious agent. Centralized vent layouts could provide relatively more consistent performance on removing droplets, whilst some local airflow recirculation with locked droplets were noticed.