Laboratory evaluation of airborne microbial reduction by an ultraviolet light positioned in a modified hollow ceiling fan blade

Ultraviolet (UV) light inactivation of bacteria has been well documented; however, few practical applications use UV light as a germicidal agent for indoor air sanitation. This study is a laboratory evaluation of the germicidal efficacy of a hollow ceiling fan blade assembly containing a UV light unit through which selected aerosolized test microorganisms were passed. An experimental system was constructed to simulate the airflow through a rotating hollow fan blade, consisting of an airtight airflow system that housed the statically positioned fan blade unit containing the UV light (power intensity, 64 × 104μW/cm2), a microbiological aerosol generation system, and a biological air-monitoring system with sampling ports located upstream and downstream of the UV light. Escherichia coli, Micrococcus luteus, and Bacillus subtilis were aerosolized and separately passed through the hollow UV light-fan blade assembly. Air sampling was conducted using modified all glass impingers. For a single pass (26 msec) of the aerosolized bacteria through the hollow UV light fan blade, reductions of 72.8, 3.8, and 8.6% were achieved for E. coli, M. luteus, and B. subtilis, respectively. No statistically significant reductions were observed in control runs with the UV light turned o ff. Copyright 1995, American Industrial Hygiene Association