| Air filtration with air cleaners (AC) and upper-room air ultraviolet germicidal irradiation (UVGI) are engineering control technologies that can remove or inactivate airborne biological particulate matter (bioaerosols) in indoor environments. The effectiveness for reducing bioaerosol concentrations, and the rate of concentration reduction of these two technologies were investigated in environmentally-controlled chamber studies and field settings.; The performance of five commercially available, and one prototype air cleaner, many of which contained ultraviolet lights, was investigated. In controlled chamber studies, air cleaners were challenged with bacterial and fungal aerosols with and without an upper-room air UVGI system in operation. Depending on the type of air cleaner, the average clean-air delivery rates varied from 26--981 m3 h-1 and from 1,421--2,503 m3 h-1, when using air cleaners in combination with upper-room air UVGI. Performance of air cleaners was evaluated in residences and a hospital therapy pool building. Air cleaners were effective in removing/inactivating airborne bacteria; reduction of airborne endotoxin was not observed.; The efficacy of upper-room air UVGI was evaluated for inactivating airborne fungal spores. The equivalent clean-air delivery rate for upper-room air UVGI inactivation of airborne Aspergillus versicolor was 35 m 3 h-1. The Z value (inactivation rate normalized to spherical UV irradiance) for Aspergillus versicolor was determined to be 1.2 x 10-4 cm2 muW -1 s-1.; The response of airborne bacteria to ultraviolet germicidal irradiation applied to ductwork in mechanical ventilation systems was also investigated. In-duct UVGI at the airstream velocity of 2.2 m s-1 inactivated culturable Mycobacterium parafortuitum by 99% and 87% in the room air and supply air duct, respectively. No significant inactivation in room air or supply air duct was observed at an airstream velocity of 5.1 m s-1.; Novel sampling methods for airborne endotoxin were developed in environmentally-controlled chamber studies using Escherichia coli and Serratia marcescens. Airborne endotoxin concentrations sampled by swirling liquid impingers, filter cassettes, and a micro orifice uniform deposit impactor (MOUDI) were not significantly different. Total airborne bacteria and endotoxin concentrations were measured at three homes. Airborne endotoxin was associated with fine airborne particle matter <1 mum in aerodynamic diameter. Total airborne bacteria and endotoxin inside were not significantly different than those levels measured immediately outside. |
