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.