Infection-prevention performance of local exhaust ventilation under three different underfloor air distribution systems during a face-to-face conversation

This study proposes using a local exhaust ventilation system (LEV) to prevent airborne infections, especially for short-range conversations. We compared the performance of a hood in three different underfloor air distribution systems (UFAD): floor-supply displacement ventilation (FSDV), horizontal flow-type floor diffuser (HFD), and swirling flow-type floor diffuser (SFD). Two situations were considered: Case A, a consulting room, and Case B, a restaurant or meeting room. The difference in infection risk assessment between using CO2 and artificial saliva particles as tracers of exhaled breath was also discussed. Results indicate that the distribution of exhaled air and infection risk for doctors decreased in the order FSDV