Performance of local ventilation system under three different underfloor air distribution systems in consulting room

This research proposed using a local exhaust system (LEV) to prevent airborne infection, especially for close-distance conversion in a consulting room. LEV is mainly used in factories and kitchens, well known as a hood, to eliminate harmful air contaminants without spreading. Because the hood’s capture efficiency is mainly affected by surrounding airflow, we compared the performance of LEV in various airflow conditions by changing underfloor air distribution systems (UFAD): floor-supply displacement ventilation (FSDV), displacement-flow-type diffuser (DFD), and swirling flow type diffuser (SFD). In floor-supply displacement ventilation (FSDV), supply air comes from the whole floor through carpets or panels, forming an ideal piston flow. A displacement-flow-type diffuser (DFD) forms thermal stratification by supplying horizontal flow along the floor. The Swirling-flow type diffuser (SFD) supplies swirling flow and mixes room air well. In a consulting room, there are two persons sitting face to face. One is an infected patient, and the other is a doctor. The patient’s mouth emits the tracer gas and artificial saliva particles, simulating droplet and droplet nuclei. Full-scale experiments were carried out to reveal the relationship between the ventilation system (LEV with FSDV, DFD, and SFD) and infection risk.