The installation of upper-room ultraviolet germicidal irradiation (UVGI) devices in ventilated rooms has the potential to reduce transmission of infections by an airborne route. However, the performance of such devices is dependant on several factors including the location of the lamp and the ventilation airflow in the room. This study uses a CFD model to evaluate the performance of UVGI devices by considering the cumulative UV-C dose received by the bulk room air in a ventilated room. By evaluating the UV dose rather than the resulting micro-organism inactivation the methodology can be used to optimise UVGI systems at the design stage, particularly when the source location of bioaerosol contaminants is not known. The study investigates the relationships between the lamp location, lamp power, ventilation system and room heating in a small, ventilated room. The results show that with ventilation air supplied at low level and extracted at high level the UVGI system performs better than with the air supplied at high level and extracted close to the floor. In addition the results show the presence of a heater in the room is unlikely to have a detrimental effect on performance and may promote mixing to increase the extent of disinfection.
UV-C light produced by lamps with high spectral emissions at 254nm has been known for many years to have a lethal effect on micro-organisms.1 The photons of light are absorbed by the micro-organism’s nucleic acid to produce pyrimidine dimers and other photo-products which can result in irreparable damage to the organism . This sensitivity of micro-organisms to UV-C light has been exploited by manufacturers to develop ultraviolet germicidal irradiation (UVGI) devices for the disinfection of air, water and surfaces for use in a wide range of applications in health care facilities, the domestic water supply and the food industry.