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Development of a test system to evaluate procedures for decontamination of respirators containing viral droplets.

Vo-E; Rengasamy-S; Shaffer-R
Appl Environ Microbiol 2009 Dec; 75(23):7303-7309
The aim of this study was to develop a test system to evaluate the effectiveness of decontamination procedures for respirators contaminated with viral droplets. MS2 coliphage was used as a surrogate for pathogenic viruses. A viral droplet testing system was constructed and the size distribution of viral droplets loaded directly onto the respirator was characterized using an aerodynamic particle sizer. The size distribution was in the range of 0.5-15 Ám, with the majority of the droplets centered in the range of 0.74-3.5 Ám. Results also showed that the droplet testing system generated similar droplet concentrations (particle counts) at different respirator locations. The test system was validated by studying the relative decontamination efficiencies of sodium hypochlorite (bleach) and ultraviolet (UV) irradiation against droplets containing MS2 virus on filtering facepiece respirators. It was hypothesized that the more potent decontamination treatments would result in a correspondingly larger decrease in the number of viable viruses recovered from the respirator. Sodium hypochlorite doses of 2.75-5.50 mg/L with a 10 min decontamination period resulted in approximately 3-4 log reductions of MS2 coliphage. By using higher sodium hypochlorite doses ( 8.25 mg/L) with the same contact time as used for the dilute solutions of 2.75-5.50 mg/L, all MS2 was inactivated. For the UV decontamination at 254 nm wavelength, approximately 3 log reduction of MS2 virus was achieved using 4.32 J/cm2 dose (3 hours contact time with UV intensity of 0.4 mW/cm2) while with the higher UV irradiation dose ( 7.20 J/cm2; UV intensity = 0.4 mW/cm2 and contact times 5 hours), all MS2 was inactivated. These findings may lead to the development of a standard test method for respirator decontamination when challenged by viral droplets.
Airborne-particles; Analytical-processes; Biological-effects; Biological-monitoring; Decontamination; Exposure-assessment; Microorganisms; Personal-protective-equipment; Qualitative-analysis; Respirators; Respiratory-equipment; Respiratory-protective-equipment; Risk-analysis; Safety-engineering; Safety-research; Standards; Statistical-analysis; Viral-diseases; Viral-infections
Ronald Shaffer, National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory, 626 Cochrans Mill Road, Pittsburgh, PA 15236
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Journal Article
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Healthcare and Social Assistance
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Applied and Environmental Microbiology