Exploring the potential to mitigate airborne transmission risks with convective and radiant cooling systems in an office

Based on the recognized airborne infection risk, there is a raised demand to develop innovative ventilation systems to mitigate the airborne transmission risk indoors. This paper focused on two micro-environment ventilation systems, namely personalized ventilation combined with radiant panel system (PVRP) and a local low velocity unit combined with radiant panel system (LVRP) and studied the potential to minimize the airborne infection risk. The performance was compared with a typical mixing ventilation system, where supply air is released from a perforated duct. The droplet nuclei of an infected person were simulated with tracer gas (SF₆) released by a thermal breathing manikin. The effect of the heat gain (38 W/m² and 73 W/m²), breathing pattern of the infector (exhaled via the nose or mouth), desk partition wall, and air distribution methods on the infection risk were studied. The results show the infection risk of the exposed person is around 0.5 % with micro-environment systems (42 l/s) and 0.7% (61 l/s) with the perforated duct system when the occupants remain for 102 min in the space. The higher heat gain slightly increased the infection risk (from 0.71 % to 0.81 %) with the LVRP system, but it did not have an effect with the PVRP system. The desk partition wall could reduce the infection risk only to an extent. The breathing patterns of the infector do not have any influence on the infection risk for the three studied air distribution methods.