Effect of moist heat reprocessing of N95 respirators on SARS-CoV-2 inactivation and respirator function

Abstract

BACKGROUND: Unprecedented demand for N95 respirators during the coronavirus disease 2019 (COVID-19) pandemic has led to a global shortage of these masks. We validated a rapidly applicable, lowcost decontamination protocol in compliance with regulatory standards to enable the safe reuse of N95 respirators. METHODS:We inoculated 4 common models of N95 respirators with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and evaluated viral inacti vation after disinfection for 60 minutes at 70°C and 0% relative humidity. Similarly, we evaluated thermal disinfection at 0% to 70% relative humidity for masks inoculated with Escherichia coli. We assessed masks subjected to multiple cycles of thermal disinfection for structural integrity using scanning electron microscopy and for protective functions using standards of the United States National Institute for Occupational Safety and Health for particle filtration efficiency, breathing resistance and respirator fit. RESULTS:A single heat treatment rendered SARS-CoV-2 undetectable in all mask samples. Compared with untreated inoculated control masks, E. coli cultures at 24 hours were virtually undetectable from masks treated at 70°C and 50% relative humidity (optical density at 600 nm wavelength, 0.02 ± 0.02 v. 2.77 ± 0.09, p < 0.001), but contamination persisted for masks treated at lower relative humidity. After 10 disinfection cycles, masks maintained fibre diameters similar to untreated masks and continued to meet standards for fit, filtration efficiency and breathing resistance. INTERPRETATION:Thermal disinfection successfully decontaminated N95 respirators without impairing structural integrity or function. This process could be used in hospitals and long-term care facilities with commonly available equipment to mitigate the depletion of N95 masks.Early release, published at www.cmaj.ca on July 30, 2020. Subject to revision.

Ultraviolet-C as a Viable Reprocessing Method for Disposable Masks and Filtering Facepiece Respirators

“…Facing this crisis, multiple organizations throughout the world (e.g., the F.D.A., the C.D.C., the E.C.D.C., the U.N.) have adjusted their infection control measures [ 14 ], issuing special authorizations for sterilizing SUPPE [ 15 , 16 , 17 , 18 ], as well as reports/guidelines about multiple reprocessing methods [ 19 , 20 , 21 , 22 , 23 , 24 ]. Even though such changes in perspective happened, there is still no universal option for reprocessing SUPPE.…”

“…Even though such changes in perspective happened, there is still no universal option for reprocessing SUPPE. This lack of universal choice happens because each option may affect SUPPE’s efficiency and integrity, diminishing its barrier capability [ 1 , 4 , 7 , 8 , 10 , 14 ]. Given that there is no universal choice, reprocessing SUPPE must consider their materials, topologies, the resources at hand, and the markets’ acceptance [ 3 , 12 , 25 ].…”

Decontamination methods for respiratory protection mask model N95: a rapid review

“…The use of dry heat was evaluated for by eleven different experimental studies. 27,28,[40][41][42]47,52,[59][60][61]66 Temperatures between 70 and 85 °C did not affect the structural characteristics of the masks under various humidity conditions (≤100% RH). 28,42 The ltering e ciency remained acceptable (≥95%) up to 50 cycles at 85 °C and 30% of RH.…”

“…Nine studies 24,26,27,33,37,42,48,49,62 evaluated the effect of moist heat between 60 and 100°C. The method did not alter mask t, odor or comfort.…”

Pulsed broad-spectrum UV light effectively inactivates SARS-CoV-2 on multiple surfaces

“…Because of the importance of respiratory protection and shortages of personal protective equipment, methods to disinfect and reuse N95 filtering respirators has also been of significant interest [15,16]. UV light as well as other methods have been either proposed or tested as a means to disinfect N95 masks and other PPE [16][17][18][19][20][21][22][23][24].…”