Reprocessing N95 Respirators During the COVID-19 Pandemic: Moist Heat Inactivates SARS-CoV-2 and Maintains N95 Filtration

Abstract

<jats:p>Background: The unprecedented demand and consequent global shortage of N95 respirators during the COVID-19 pandemic have left frontline workers vulnerable to infection. To potentially expand the supply, we validated a rapidly applicable low-cost decontamination protocol in compliance with regulatory standards to enable the safe reuse of personalized, disposable N95-respirators. Methods: Four common models of N95-respirators were disinfected for 60 minutes at 70°C either at 0% or 50% relative humidity (RH). Effective inactivation of SARS-CoV-2 and E. coli was evaluated in inoculated masks. The N95 filter integrity was examined with scanning electron microscopy. The protective function of disinfected N95 respirators was tested against US NIOSH standards for particle filtration efficiency, breathing resistance and respirator fit. Results: A single heat treatment inactivated both SARS-CoV-2 (undetectable, detection limit: 100 TCID50/ml) and E. coli (0 colonies at 50%RH) in all four respirator models. Even N95-respirators that underwent ten decontamination cycles maintained their integrity and met US governmental criteria for approval regarding fit, filtration efficiency and breathing resistance. Scanning electron microscopy demonstrated maintained N95 fiber diameter compared to baseline. Interpretation: Thermal disinfection enables large-scale, low-cost decontamination of existing N95-respirators using commonly sourced equipment during the COVID-19 pandemic. This process could be used in hospitals and long term care facilities and also provides a feasible approach to expand the N95 supply in low- and middle-income regions.</jats:p>

A systematic review of mask disinfection and reuse for SARS-CoV-2 (through July 10, 2020)

“…Of the 58 7, 12-68 mask disinfection and reuse articles, ten were reference chained including nine 59-67 from three systematic reviews 69-71 , and one 68 from another article 15 . Of these 58 articles, 30 (52%) were preprints at the time of download 12-16, 23-27, 33, 39-45, 49, 50, 55-63, 66 , and one (2%) was data generated by an FDA contractor with no indication of peer review 68 .…”

“…Overall, 16 studies measured disinfection and durability 12, 15, 19, 20, 22, 27-30, 33, 36, 47, 49, 51, 62, 64 , 16 studies measured only disinfection 13, 18, 23, 24, 31, 38, 40, 41, 43, 44, 48, 56, 63, 65-67 and 26 studies measured only durability 7, 14, 16, 17, 21, 25, 26, 32, 34, 35, 37, 39, 42, 45, 46, 50, 52-55, 57-61, 68 . Thus, 32 studies measured disinfection and 42 measured durability.…”

“…In total, 92 individual mask disinfection tests were conducted across 32 studies 12, 13, 15, 18-20, 22-24, 27-31, 33, 36, 38, 40, 41, 43, 44, 47-49, 51, 56, 62-67 . The masks tested included: 75 tests with N95s (82%), 5 (5%) with cloth masks, 4 (4%) with surgical masks, three (3%) with KN95s, three (3%) with Tyvek, and 1 (1%) with a plastic face shield and 1 (1%) unspecified.…”

“…In the 15 SARS-CoV-2 N95 mask samples, eight were chemical (hydrogen peroxide 15, 29, 30, 36, 48 , ethanol 15, 29 , peracetic acid 30 ), four were radiation (PX-UV 13 , UVGI 15, 29, 31 ), and three were thermal (autoclave 30 , dry heat 29, 49 ). All applications of hydrogen peroxide (10-210 minute exposure), ethanol (spraying, saturation), and 10% peracetic acid (60 minute exposure) achieved SARS-CoV-2 inactivation or >3 log reduction.…”

“…In total, 159 individual mask reuse tests were conducted in 42 studies 7, 12, 14-17, 19-22, 25-30, 32-37, 39, 42, 45-47, 49-55, 57-62, 64, 68 . The masks tested included: 114 tests with N95s (72%), an additional four tests with KN95s (2.5%), seven tests with folded or molded or HKYZ N95s (4.4%), four tests with FFPs (2.5%), and two tests with respirator fabric (1%).…”