Comparative Evaluation of Quantitative Test Methods for Gases on a Hard Surface
Technical Report,01 Apr 2008,28 Feb 2017
ARMY EDGEWOOD CHEMICAL BIOLOGICAL CENTER APG MD ABERDEEN PROVING GROUND
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In this study, two quantitative test methods were evaluated the Three Step Method TSM and the Quantitative Disk Carrier Test QCT for determining the efficacy of chlorine dioxide CD gas and vaporous hydrogen peroxide VHP against spores of Bacillus subtilis. The tests were performed at three efficacy levels low, medium, and high. Steel carriers, inoculated with 7 logs of spores, were exposed to 250, 500, and 3000 parts per million volume ppmvh concentration time CT of CD gas or 150, 450, and 900 ppmvh CT of VHP. For the high-CD treatment, testing resulted in a narrow range of log reduction LR67 for both methods however, for the medium- and low-CD treatments, the variable LR values ranged between 4 and 5 for QCT and 2 and 4.5 for TSM. The standard deviation SD 0.52.5 log was high for the medium- and low-CD treatments. For VHP, a value of 6 LR was observed with QCT for each treatment level, and mean LR values of 2, 3.5, and 4.5 for the low, medium, and high treatment levels, respectively, were observed with TSM. TSM was more sensitive to the treatment level, and the high variability could have resulted from poor gas penetration.
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