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Civil and Environmental Engineering


Civil and Environmental Engineering

Description or Abstract

UV is a proven decontamination tool for microbial pathogens, including the SARS-CoV-2 virus. Lower log inactivation was observed on FFRs than would have been predicted by aqueous-based UV dose-response data for MS-2 bacteriophage and E. coli. Results have demonstrated that FFR materials yield varying results in terms of effective disinfection in experiments conducted on KN95 and N95 face respirators. The highest inactivation for both surrogates was observed with respirator KN95 B. The respirator yielded 3 and 2.75 log inactivation for E. coli and MS-2, respectively at UV doses of 1500 mJ/cm2. KN95 A yielded the lowest inactivation for MS-2 at 0.75 log when exposed to 1000 mJ/cm2.

The observed log inactivation produced by UV devices when treating PPE were lower than predicted by the aqueous UV dose-response curves. In addition, the dose-response curves did not follow the trends commonly observed with aqueous data. In general, dose-response curves increase until they reach a maximum inactivation, where they plateau. The dose-response curves for the respirators had a semicircle shape, where the inactivation reached a peak and then decreased. This decrease in UV inactivation is thought to be due to the degradation of the fibers of the FFR, allowing for more viral and bacterial cells to wash through the layers of the respirator. This degradation phenomenon was observed at UV doses at and above 2000 mJ/cm2.

To further test the degradation theory, the N95 8210 and KN95 B FFRs were cut into coupons, where the layers were separated. These experiments used a collimated beam device, where the penetrated irradiance value and the ability of each layer to retain MS-2 were quantified. The results of the experiments varied from the intact FFR degradation experiments but displayed some data to support the degradation theory. Research findings strongly suggest that the impacts of UV-C treatment on FFR material degradation should be confirmed using microbial surrogates in addition to abiotic particles.


Grant/Award Number and Agency

University of New Hampshire, Collaborative Research Excellence (CoRE) Initiative


Public (open access)