Low-cost moist heat treatment of N95 masks eliminates coronavirus: Study

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Scientists have found that moist heat treatment of N95 masks eliminates the novel coronavirus which causes COVID-19, an advance which could allow reuse of these scarce resources in hospitals and long-term care facilities.

According to the study, published in Canadian Medical Association Journal (CMAJ), moist heat treatment of masks for 60 min at 70 degrees Celsius in a humid condition did not damage their structure or affect function.

"A single heat treatment rendered SARS-CoV-2 undetectable in all mask samples," the scientists, including those from the University of Toronto in Canada, wrote in the study.

"This low-cost reprocessing strategy can be applied 10 times without affecting the mask's filtration, breathing resistance, fit and comfort, and thus may help to alleviate the global shortage during the COVID-19 pandemic," said study co-author Gregory Borschel from The Hospital for Sick Children (SickKids) in Toronto, Canada.

In the study, the researchers tested four common models of N95 masks at various temperatures and humidity levels to determine whether the virus could be detected on the treated masks.

They assessed masks subjected to multiple cycles of thermal disinfection for structural integrity using powerful microscopes, and for protective functions using standards of the US National Institute for Occupational Safety, and Health for particle filtration efficiency, breathing resistance and respirator fit. They also analysed fibre samples for structural integrity and assessed function of the masks after treatment with heat.

"After 10 disinfection cycles, masks maintained fibre diameters similar to untreated masks and continued to meet standards for fit, filtration efficiency, and breathing resistance," the study noted.

The researchers believe the process could be used in hospitals and long-term care facilities with commonly available equipment to mitigate the depletion of N95 masks.
"Thermal disinfection of N95 masks may provide a low-cost, effective method for regions with fewer resources to extend their supply of these critical resources, thereby protecting vulnerable front-line workers from job-related risk of infection," Borschel said.