As people spend a greater portion of their time indoors, the likelihood of exposure to biohazards in indoor air is increasing. This study developed a system to disinfect indoor bioaerosols while protecting occupants from direct exposure to ozone. This hybrid approach combines high concentrations of ozone generated by a non-thermal dielectric barrier discharge system, and an ozone decomposition unit using MnO2/Al2O3 and MnO2/AC catalysts. Four types of common bioaerosols were used to test the germicidal efficacy of 0-175 ppm ozone at a relative humidity of 30-70% and retention time of 1-10 s. The results indicate that the germicidal efficacy of ozone on E. coli, C. famata and P. citrinum spore bioaerosols increased with ozone concentration, relative humidity, and retention time; however, the process was less effective with the hardy endospores of B. subtilis. Germicidal efficacy of 90% was obtained for bioaerosols (two vegetative cells and one spore) using high concentrations of ozone at a relative humidity of 70% and exposure time of 10 s. Residual ozone in the tail gas was decomposed to undetectable levels using catalysts at a gas hourly space velocity of 3.287 x 10(3) 1/h. The concentration of indoor bioaerosols (total bacteria and fungi) in a small office was reduced to below 50 CFU/m(3) and ozone in the tail gas was reduced to undetectable levels following treatment for 2 h. The hybrid system of ozone disinfection and catalysts provides high germicidal efficacy while protecting occupants from direct exposure to ozone.
