Room Air Disinfection by Ultraviolet Irradiation of Upper Air

Abstract

Room air disinfection by upper air UV was studied in relation to temperature gradients. When upper air temperature minus lower air temperature ranged between +7 and -2 F, the rate of disappearance of test organisms from the lower air, with two UV fixtures operating, averaged 33 equivalent air changes per hour (AC/hr), and when the temperature difference ranged between -3 and -5 F, the rate of disappearance averaged 83 AC/hr. Estimates indicated that the rate of air exchange between the upper and lower parts of the room averaged about 25 AC/hr when air entering at the ceiling was warmer than lower room air and exceeded 125 AO/hr when air entering at the ceiling was 3 F or more cooler than the air in the lower part of the room.