The effectiveness of UV irradiation on vegetative bacteria and fungi surface contamination

Ultraviolet irradiation has been used in the indoor environment to eliminate or control infectious diseases in medical care facilities. Heating, ventilating, and air-conditioning (HVAC) system components such as duct-liners, cooling coils, drip pans, interior insulation and areas subjected to high levels of moisture can create an environment which is prone to biological contamination on surfaces. The movement of indoor air being dominated by HVAC system operation can carry biological contaminants which can expose large numbers of building occupants to bioaerosols. The use of germicidal ultraviolet lamps (UVGI) in commercial and residential HVAC systems has increased. UVGI treatment has focused on HVAC component internal surfaces and airflow. A method to determine the antimicrobial efficacy of UVGI irradiation was developed and tested on the surface of agar plates with four species of vegetative bacteria and seven species of fungi. The percent kill and the kinetics of the rate of killing, k value, were calculated for each organism.