Abstract: An air disinfection method and unit are disclosed in which air is passed through a housing from an air inlet to an air outlet opening at a predetermined air flow rate under substantially uniform cross-sectional air flow conditions across closely spaced UV-C irradiation lamps located at a distance of between 2 to 4 inches O. C. with the lamps being positioned directly in the air stream so that all air flows passed the bulbs at a distance of not more than 2-3 inches. The bulbs produce UV-C irradiation at a wave length of about 254 nm and have an intensity of about 142 .mu.W/cm.sup.2. The housing has a predetermined volume selected such that airborne bacteria remain in the enclosure for a residence time of between 0.5 and 1.5 seconds.