title: Control of aerosol contaminants in indoor air: combining the particle concentration reduction with microbial inactivation.
abstract: An indoor air purification technique, which combines unipolar ion emission and photocatalytic oxidation (promoted by a specially designed RCI cell), was investigated in two test chambers, 2.75 m3 and 24.3 m3, using nonbiological and biological challenge aerosols. The reduction in particle concentration was measured size selectively in real-time, and the Air Cleaning Factor and the Clean Air Delivery Rate (CADR) were determined. While testing with virions and bacteria, bioaerosol samples were collected and analyzed, and the microorganism survival rate was determined as a function of exposure time. We observed that the aerosol concentration decreased approximately 10 to approximately 100 times more rapidly when the purifier operated as compared to the natural decay. The data suggest that the tested portable unit operating in approximately 25 m3 non-ventilated room is capable to provide CADR-values more than twice as great than the conventional closed-loop HVAC system with a rating 8 filter. The particle removal occurred due to unipolar ion emission, while the inactivation of viable airborne microorganisms was associated with photocatalytic oxidation. Approximately 90% of initially viable MS2 viruses were inactivated resulting from 10 to 60 min exposure to the photocatalytic oxidation. Approximately 75% of viable B. subtilis spores were inactivated in 10 min, and about 90% or greater after 30 min. The biological and chemical mechanisms that led to the inactivation of stress-resistant airborne viruses and bacterial spores were reviewed.
authors.affiliation: Center for Health-Related Aerosol Studies, Department of Environmental Health, University of Cincinnati, 3223 Eden Avenue, PO Box 670056, Cincinnati, Ohio 45267-0056, USA. sergey.grinshpun@uc.edu
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Grinshpun
authors.forename: Atin
authors.initials: A
authors.lastname: Adhikari
authors.forename: Takeshi
authors.initials: T
authors.lastname: Honda
authors.forename: Ki Youn
authors.initials: KY
authors.lastname: Kim
authors.forename: Mika
authors.initials: M
authors.lastname: Toivola
authors.forename: K S Ramchander
authors.initials: KS
authors.lastname: Rao
authors.forename: Tiina
authors.initials: T
authors.lastname: Reponen
mesh_terms: D000336:Aerosols / Q000032:analysis*; D000393:Air Pollutants / Q000737:chemistry*; D016902:Air Pollution, Indoor / Q000517:prevention & control*; D002384:Catalysis; D004867:Equipment Design; D005069:Evaluation Studies as Topic; D010084:Oxidation-Reduction; D010777:Photochemistry; D013171:Spores, Bacterial / Q000528:radiation effects; D014691:Ventilation / Q000295:instrumentation*; D014771:Virion / Q000528:radiation effects
chemical_list: D000336:Aerosols; D000393:Air Pollutants