OBJECTIVES: The indoor environment of modern office buildings represents a new ecosystem that has been created totally by humans. Bacteria and fungi may contaminate this indoor environment, including the ventilation systems themselves, which in turn may result in adverse health effects. The objectives of this study were to test whether installation and operation of germicidal ultraviolet (GUV) lights in central ventilation systems would be feasible, without adverse effects, undetected by building occupants, and effective in eliminating microbial contamination. METHODS: GUV lights were installed in the ventilation systems serving three floors of an office building, and were turned on and off during a total of four alternating 3 week blocks. Workers reported their environmental satisfaction, symptoms, as well as sickness absence, without knowledge of whether GUV lights were on or off. The indoor environment was measured in detail including airborne and surface bacteria and fungi. RESULTS: Airborne bacteria and fungi were not significantly different whether GUV lights were on or off, but were virtually eliminated from the surfaces of the ventilation system after 3 weeks of operation of GUV light. Of the other environmental variables measured, only total airborne particulates were significantly different under the two experimental conditions--higher with GUV lights on than off. Of 113 eligible workers, 104 (87%) participated; their environmental satisfaction ratings were not different whether GUV lights were on or off. Headache, difficulty concentrating, and eye irritation occurred less often with GUV lights on whereas skin rash or irritation was more common. Overall, the average number of work related symptoms reported was 1.1 with GUV lights off compared with 0.9 with GUV lights on. CONCLUSION: Installation and operation of GUV lights in central heating, ventilation and air conditioning systems of office buildings is feasible, cannot be detected by workers, and does not seem to result in any adverse effects.
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