Characterization of ultraviolet upper room air disinfection devices

Ultraviolet germicidal irradiation (UVGI) is one method currently used to r educe transmission of airborne infectious diseases such as tuberculosis. UV GI is defined as optical radiation in the shortwave UV-C spectrum capable o f killing microorganisms and has been demonstrated to be effective against certain airborne bacteria. Because prolonged direct exposure to low intensi ty UVGI can cause skin and eye irritation, fixtures appropriate for upper r oom air disinfection are installed above eye level and designed to limit th e vertical emission spread to prevent excessive exposure to occupants, Accu rate UVGI fixture emission profiles, in combination with appropriate room v entilation measurements, are needed to calculate the dose to airborne micro organisms and estimate the effectiveness of these air disinfection devices in preventing disease transmission in susceptible populations. Manufacturer s of fixtures usually provide nominal wattage and horizontal centerplane in tensity levels, but to quantify the dose to exposed airborne microorganisms adequately in realistic room applications it is necessary to measure the t hree-dimensional emission profile for various fixture designs. This article evaluates several UVGI fixtures available for upper room installations and illustrates practical methods for evaluating effective radiation output. T ypical emission diagrams are included.