Manitoba researchers say they may have found a way to safely reuse N95 masks amid COVID-19 crisis

By | April 2, 2020

A group of Manitoba researchers say they’ve found a way to safely decontaminate and reuse some types of medical masks that are normally thrown away after each use.

The COVID-19 pandemic has caused global shortages of personal protective equipment for health-care workers, including N95 respirators and masks.

A team of five Manitoba researchers released a study Wednesday that tested decontamination of four types of masks, finding some success.

Led by Dr. Anand Kumar, a professor of medicine at the University of Manitoba, the study said preliminary results suggest some masks could be successfully decontaminated and reused up to 10 times using common sterilization techniques.

“It became apparent in the early course of the epidemic that we were going to burn through personal protective equipment quite rapidly,” said Kumar, who also works as a critical care physician at Winnipeg’s Health Sciences Centre and has a background in infectious diseases.

Shortages reported

Medical masks are designed to filter out aerosol particles, with the N95 providing the best protection against tiny aerosol particles that carry the novel coronavirus.

In the early stages of the pandemic, shortages of N95 masks and other personal protective gear were being reported, Kumar said.

Dr. Anand Kumar says the sterilization methods his team tested could help to address the global shortage of N95 masks. (John Woods/The Canadian Press)

“Physicians and other health-care workers were having to use their masks and other equipment for days on end, which is specifically recommended against,” he said.

That prompted the physician to start exploring ways to reuse masks, which are often discarded after each patient and may only be worn for a few minutes each time.

About 10 days ago, Kumar’s team began experimenting with four types of masks that were available within Winnipeg, using four different types of sterilization methods.

Working 18-hour days, the team assembled a paper that has been submitted to a medical site that shares preliminary results with others around the world. 

Some masks recycled up to 10 times

The goal of the study was to see if the masks could be successfully decontaminated without losing structural integrity or effectiveness.

Two of the methods, Kumar said, successfully allowed for multiple cleanings with no loss of function in terms of filtering ability.

One of those methods, using vaporized hydrogen peroxide, was very effective in decontaminating all types of masks while preserving their effectiveness, Kumar said. However, he added the technology is only available in a few places in North America

A more common method, autoclaving, which is found in nearly every hospital setting, was also very effective, he said.

“[Autoclaving] is like a pressure cooker — basically you enclose items into a chamber, you lock down the chamber, you heat it up and actually increase the pressure inside the chamber,” Kumar said.

The machines heat up to about 121 C for 15 minutes, killing bacteria and viruses. “It’ll sterilize anything.”

Kumar said one type of pleated mask that was tested was safely decontaminated up to 10 times using autoclaving, a standard disinfecting tool that uses heat to sterilize hospital equipment. (Ivanoh Demers/Radio-Canada)

“The assumption has been that if you tried this on an N95 mask they would degrade rapidly. We thought we’d give it a try anyway,” Kumar said.

“And actually what we found is while it does degrade some [types of] masks, there’s a certain group of masks that are made of kind of a fabric-type material, rather than being moulded closely to the face… they’re called pleated [masks],” he said.

‘Ready to go right now’

Kumar said the pleated fabric masks can be cycled through an autoclaving machine 10 times and come out as good as before.

“The reason this is really important is that autoclaves are available at literally every established hospital in the world. There is probably no hospital in the world that doesn’t have an autoclave machine,” Kumar said.

“So everybody can use this for these particular types of masks and these particular types of masks are probably the most common type of N95 mask, so we’re really pleased.”

Kumar said the technique could be put into use at any hospital at any time. “It’s a technology that’s available and ready to go right now.”

Kumar found certain fabric masks, like the one above, can be cleaned successfully using the autoclave method. (Submitted by Dr. Anand Kumar)

In order to test the masks in a hospital setting, the team used a non-pathogenic virus as a stand-in for COVID-19, Kumar said.

Further testing was carried out at the National Microbiology Laboratory in Winnipeg, which used the SARS-CoV-2 virus, the one responsible for COVID-19.

The study is based on preliminary testing results and has not yet been peer-reviewed or published in a medical journal.

‘Other people need to test it’

Kumar noted that the testing was done using only the four kinds of masks inside a lab using surface contact with the viruses. The methods haven’t been tested with masks that have actually been worn by health-care workers in the field.

“Although we tested the functional integrity of decontaminated masks via quantitative fit testing, our testing cannot take into account the respirator’s ability to withstand the rough handling that extended wear by health-care workers, with stress and perspiration, can inflict,” the study states.

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Kumar said he wouldn’t recommend heavily worn or soiled masks be decontaminated, but said many masks could be suitable for the process. 

“A lot of times when we use a mask we may put on the mask and go into an ill patient’s room, work for three or four minutes, come back out and then you might discard the mask,” he said.

“Those are the masks that you want to consider reprocessing. But as I said, if that mask is otherwise damaged or showing substantial signs of wear and tear, then that’s probably not one you want to recycle.”

Kumar hopes at the very least health-care systems could start saving the masks to be decontaminated later, should the need arise. He also said others may want to replicate his results before implementing them. 

“I think it works, my team thinks it works, but in science, before you accept something as being true, it’s got to be duplicated, so other people need to test it and find that they agree with us.”

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