Room Air Disinfection by Ultraviolet Irradiation of Upper Air

Abstract

Disinfection of air in lower part of a room by ultraviolet irradiation of upper air has been studied after artificial dissemination of test organisms (Serratia marcescens). On basis of disinfection rates in lower air with different intensities of UV in upper air, the rates at which organisms are killed in upper air and at which air mixes between upper and lower parts of the room were calculated. By performing studies under different conditions of air motion, it was possible to analyze factors affecting air mixing and upper-air disinfection. With no fans to increase air motion, a single 30-w UV tube increased the rate of disappearance of organisms from lower part of room by the equivalent of 61 air changes per hour (median value). With a large-bladed ceiling fan, the same UV tube almost doubled the rate of disappearance of organisms.