Fit Testing Failure of Reprocessed "Duckbill"-Type N95 Masks

In response to worldwide shortages of N95 masks during the severe acute respiratory syndrome-coronavirus-2 pandemic, various strategies have been used. The Centers for Disease Control and Prevention recommend several strategies, including simple isolation to reprocessing methods using vaporized hydrogen peroxide to guide reuse of masks up to five times. National Institute for Occupational Safety and Health (NIOSH) quantitative fit testing was performed after five trials of donning and doffing in one cohort of new masks and two cohorts of repeatedly sterilized "duckbill"-type N95 masks.

One cohort of new masks and two cohorts of sterilized masks were repeatedly subjected to 35% vaporized hydrogen peroxide for either five or 10 cycles. Then, they were subjected to five trials of donning and doffing, with NIOSH quantitative fit testing performed after each wear cycle to assess for any degradation on fit performance caused by sterilization and/or repeated donning and doffing up to the recommended Centers for Disease Control and Prevention limit of five times. All of the fit testing was performed on a single volunteer.

The means and 95% confidence intervals for each cohort and the individual results for each mask within each cohort were reported. A χ² analysis showed significant differences in percentages of masks that pass fit testing in both recycled mask cohorts.

These data show the variability of NIOSH fit testing results of both new and sterilized masks. The mask recycling program of our partner health systems thus discarded these types of masks due to the variable failure rate. Health systems should consider individual evaluation to inform their overall policies on mask reuse and recycling.