Variable NIOSH Quantitative Fit Testing Failure Rates of Reused and Sterilized "Duckbill" Type N95 Masks

ABSTRACT

Study Objectives: In response to worldwide shortages of N95 masks during the SARS-CoV2 pandemic, the Centers for Disease Control and Prevention (CDC) has highlighted various conservation and reuse strategies including isolation and vaporized hydrogen peroxide but with limitations of "safe" reuse of N95 masks up to five times. The aim of this project was to evaluate the results of NIOSH quantitative fit testing after five trials of donning on a specific manufacturer's "duckbill" type N95 masks with/without repeated sterilization using vaporized hydrogen peroxide. Method(s) The cumulative effects of both repeated donning and doffing combined with repeated sterilization was evaluated using NIOSH Quantitative fit testing. Quantitative Fit testing generates an objective overall score across five separate tasks using an automated particle detection device to evaluate the integrity of both the mask materials and the seal on the participant. Two cohorts of duckbill type N95 masks were subjected to repeated cycles of 35% vaporized hydrogen peroxide (VHP) sterilization (five and ten cycles) and compared to one cohort of new unsterilized masks. All three cohorts were subjected to five trials of NIOSH quantitative fit testing following the protocol of donning the mask, NIOSH fit testing, then removal of the mask, with isolation for 24hrs. This cycle was repeated for five trials for each mask in each cohort. The fit testing trials were conducted on a single participant who has been fit tested and passed on this type and manufacturer's N95 mask. This repeated-measures design was chosen to remove the variability of facial size/shape for this study. Result(s) Overall, a total of 150 fit testing trials were conducted, 5 trials on 30 total masks, with 10 masks in each cohort (New vs 5x sterilized vs 10x sterilized). There were a total of 21/150 (14%) fit testing trial failures, with 13/30 (43%) individual masks failing at least one fit testing trial and 4/30 (17%) masks that failed a variable number of fit testing trials spread across all five trials per mask. Chi-square analysis showed a significant increase in the percentages of masks that failed fit testing in both mask cohorts which underwent VHP compared to unsterilized/New masks (New p=0.09, 5x p=0.03, 10x p=0.03). Conclusion(s) This data shows that this manufacturer's type and model "duckbill" N95 masks have a variable failure rate across repeated Quantitative NIOSH fit testing. There was an increased failure rate for masks that underwent sterilization. Our partner health system's mask recycling program thus discarded these type masks due to this variable failure rate. Health systems should thus consider individual testing to inform their overall policies on future mask reuse and/or recycling. No, authors do not have interests to disclose Copyright © 2022