Effect of Ultraviolet Germicidal Lamps on Airborne Microorganisms in an Outpatient Waiting Room

Abstract The effectiveness of 254-nm ultraviolet radiation for inactivating airborne microorganisms (and thereby reducing the spread of respiratory infections such as tuberculosis) was evaluated by collecting air samples in an occupied 90-m3 room equipped with four 15-W wall-mounted germicidal lamps. The indoor concentration of airborne bacteria was positively associated with the number of people present, the concentration of bacteria in the ventilation supply air, and the relative humidity, but was negatively associated with operation of the germicidal lamps and with the number of open windows. A generalized linear model suggested that use of the lamps reduced culturable airborne bacteria by 14 to 19 percent. This degree of air disinfection was calculated to be the equivalent of between 1.5 and 2 air changes per hour (ACHeq). This equivalent ventilation was in addition to the 1 to 2.5 ACH that open windows provided and the 8 ACH that the mechanical ventilation system supplied. The microbicidal effect of ...

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