N95 masks unsafe after second sterilization: St. B study

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This article was published 04/08/2020 (1353 days ago), so information in it may no longer be current.

A new study by St. Boniface Hospital Albrechsten Research Centre shows N95 face masks can be safely reused — once — after autoclave sterilization.

Dr. Michael Czubryt, principle investigator and lead author of the study published by Journal of Hospital Infection, said the Winnipeg centre started the project in March, driven by personal protective equipment concerns amid the COVID-19 pandemic.

“We arrange the masks on a rack and ensure the mask material itself isn’t touching any metal surfaces,” Czubryt said Wednesday. “Then we put them into the machine, and they’re heated up to 121 C for 30 minutes and then there’s a drying stage that follows after that. Once they come out, we bag them up and label when they were treated and put them into our storage.”

He added some face masks failed the fit testing after a second sterilization, making them unsafe to reuse.

Czubryt said the Winnipeg study differs from others because it takes into account “real-world use” of the masks, which cover the mouth and nose and protect the user via filtration of airborne particles. He added some studies say a N95 mask can be steralized up to 10 times, but they don’t take into account the damage PPE takes throughout a hospital shift.

“We know people are breathing through this mask for eight hours, they’re sweating into the mask and there are all sorts of issues that can happen,” he said. “What our study has found is this absolutely has a major effect on the way these masks can be reused. It basically causes the mask to break down much faster than anticipated.”

Czubryt said if a facility has 10,000 masks saved up after first use, it could hypothetically get 10,000 additional uses. However, some get damaged or stained — Czubryt said it’s likely a second use is possible some 66 per cent of the time.

“I still see this as a win,” he said. “These were intended to be a single-use, but clearly in this case with the mask that we looked at, we can get more than that out of it.

“If you’re really on the front lines and getting hit with a major wave of infections and you’re running low on supplies, that could be a real important buffer that allows you to stretch you out far enough until you get your next shipment.”

Czubryt said he hopes more hospitals use the information from the study, but he’s confident the study has helped prepare Manitoba hospitals for an increase in COVID-19 cases in the province.

“We’ve been fortunate in Manitoba not to be at the point where we run low on our front-line supply, but if we do, we’re ready to move forward with these additional masks.”

kellen.taniguchi@freepress.mb.ca