INACTIVATION OF AIRBORNE ENVIRONMENTAL BACTERIA AND FUNGI BY IN-DUCT UVC LAMPS

摘要

UV lamps have been used to inactivate airborne microorganisms for many years, with increasing activity in the 1960's. Much of the early work was directed at control of very infectious diseases (particularly TB), often in medical facilities. Wavelengths within the short wave, or C band of UV light (UVC), have been shown to be the most effective germicidal light wavelength. UVC is generated by electrical discharge through low-pressure mercury vapor (primary wavelength of 253.7 nm) enclosed in a glass tube that transmits UVC light. UVC has been shown to inactivate viruses, mycoplasma, bacteria, and fungi, whether suspended in air or deposited on surfaces. Because exposure to UV radiation is a common environmental hazard, cells have developed a number of repair mechanisms to counteract UV-induced damage that must be considered when experimentally measuring UV effects. This paper reports on a research project with the objective of evaluating UV lamps to inactivate microbial aerosols in ventilation equipment using established bioaerosol control device performance measures. The data indicated that UVC systems can be used to inactivate a substantial fraction of environmental bioaerosols in a single pass. Many of the data conflicts reported in the literature are the result of overlooking the importance of the medium the test organism is in/on during exposure. The susceptibility of an organism can be quite different when growing on an agar plate than when it is a micrometer-sized aerosol. Design based on UVC irradiance and bioaerosol exposure models, when properly applied, appears to be sufficiently accurate to allow reasonable design for control of environmental bioaerosols, provided the k-value is available. However, lamp performance values must be known or measured to use the models. Lamp output measurements must be made at the expected use conditions because output varies strongly with air temperature and flow rate.