Filtration efficiency of N95 filtering facepiece respirators during multi-cycles of '8-hour simulated donning plus disinfection'

Background: Aerosol-borne diseases such as COVID-19 may outbreak occasionally in various regions of the world, inevitably resulting in short-term shortage and corresponding reuse of disposable respirators. Aim: To investigate the effective disinfection methods, reusable duration and frequency of N95 respirators. Methods: Based on the self-built respirator simulation test system, and under combinations of experimental conditions of three N95 respirators x 0-200 nm NaCl aerosols x three simulated breathing flow rates (15, 50 and 85 L/min) x two disinfection methods (dry heating and ultraviolet (UV) radiation), this study continuously measured the changes in filtration efficiency of all respirators during multi-cycles of '8-h simulated donning + disinfection' until the penetration reached >= 5%. Findings: Multi-cycles of dry heating and UV radiation treatments on the reused (i.e., multiple 8-h donning) N95 respirators had a minimal effect (<0.5%) on the respirator filtration efficiency, and even at 85 L/min, all tested N95 respirators were able to maintain filtration efficiencies >= 95% for at least 30 h or four reuse cycles of '8-h donning + disinfection', while a lower breathing flow rate (15 L/min) plus the exhalation valve could further extend the N95 respirator's usability duration up to 140 h or 18 reuse cycles of '8-h donning + disinfection'. As the respirator wearing time extended, aerosol penetration slowly increased in a quadratic function with a negative second-order coefficient, and the penetration increment during each cycle of 8-h donning was less than 0.9%. Conclusion: Multi-cycles of N95 respirator reuse in combination with dry heating or UV irradiation disinfection are feasible. (C) 2022 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study found that multi-cycles of N95 respirator reuse with dry heating or UV irradiation disinfection are feasible. The filtration efficiency of the respirators was minimally affected during multiple reuse cycles, and the respirators were able to maintain filtration efficiencies >= 95% for at least 30 hours or four reuse cycles. Lower breathing flow rates and the presence of an exhalation valve could further extend the usability duration of the N95 respirators.