BC should allow the “logical freedom” of wearing N95s: aerosol expert

Like all masks, N95 respirators aren’t 100% effective at blocking out COVID-19—but as long as they fit relatively well, they are in most cases still more so than cloth masks and even medical masks, says a BC expert.

The Beacon spoke with UBC mechanical engineering professor Steven Rogak, who has expertise in filtration systems and aerosol science, after provincial health officer Dr Bonnie Henry said earlier this week that respirators don’t necessarily provide an advantage over other types of masks.

“I know some people have called for the increased use of respirators or N95 [masks] routinely. And I’ll just say in the majority of settings, the incremental benefit in a low-risk setting like a school or a retail store is minimal,” Henry told reporters on Tuesday.

“What is most important is that you have a good fitting mask that you wear and you wear appropriately.”

Rogak said that statement depends on what you consider “incremental.”

The size of particles

“[The N95 will] filter out typically 99.9% of the particles that would be carrying the COVID-related virus. And so, in terms of the material’s filtration properties, the N95 and the KF95 masks are more than adequate to filter everything out,” he said.

“Whereas the disposable blue pleated masks are pretty good—while the worst are the cloth masks that many people are wearing, that would probably filter out less than half of the viruses.”

It’s based on the size of airborne COVID particles, Rogak said.

“Whether it meets what traditionally was called by doctors airborne or not, it does meet what an aerosol scientist would call an aerosol and an airborne [particle]. It’s particles that are less than 10 microns, and probably above 1 micron, and many of them are about 3 microns.”

N95s are thus named because they filter at least 95% of particles that are at least 0.3 microns in diameter. The SARS-COV-2 particle, which causes COVID-19, is about 0.1 micron in size—but is always bonded together with something larger, like aerosols, that allows it to travel through the air.

How important is fit?

While Henry didn’t mention a source for her statement Tuesday that fit is more important than material, a February 2021 study from Cambridge University did make a similar hypothesis based on fit tests of seven participants. While researchers of that study acknowledged the small sample size, they said “in some cases, poorly-fitted N95 masks were only comparable with surgical or cloth masks.”

Rogak agreed that fit is extremely important in blocking out infectious particles. If a mask is hanging off your face, it will likely let in 30-50% of virus particles no matter what type it is. But he noted that N95 masks, designed to form a seal around the wearer’s mouth and nose, are actually more likely to fit the average person’s face relatively well—except perhaps in “unusual” situations.

Mikhail Moore, president of Burnaby-based PPE manufacturer Vitacore, agrees with that. Vitacore was the first manufacturer to produce Health Canada-approved N95 and N99 respirators on Canadian soil. Health Canada in turn requires respirators to qualify for certification from the Canadian Standards Association in terms of fit, and from the National Institute for Occupational Safety & Health in terms of filtration efficiency.

“Our CAN99 respirators [were] actually tested on over 2,000 frontline workers across Canada, and Canada is a great test subject in the fact that we’re a very diverse country with lots of different face shapes and sizes within healthcare specifically,” Moore told the Beacon.

“So the CAN99 was designed with the idea that we want to fit as many faces as possible. And so far, the data coming back from all the fit-testing reports that we’ve done shows that it fits about 90% of faces on a quantitative test.”

A proposal to the province

Late last month, Moore put out a proposal to the province on his Twitter account: allow healthcare workers to wear N95 masks while working at vaccine clinics, and Vitacore would donate 200,000 respirators to the government.

“Many of those healthcare professionals have said that they would [volunteer], provided that they would be able to wear a respirator, given what we now know about the transmission. And so we wanted to support the vaccination effort,” Moore said.

“So we offered to donate 200,000 respirators, specifically to the vaccination centers to help those individuals that want to volunteer their work there but needed an extra level of protection for their own peace of mind.”

It came after reports on Twitter from BC physicians that they were told they wouldn’t be allowed to wear respirators while working at vaccine clinics. Dr Victor Leung, an infectious diseases specialist in Vancouver, responded to a provincial call for volunteers to work at short-staffed clinics—only to be told he wouldn’t be able to wear an N95 or CAN99.

Leung backed out on his offer, calling the policy “irrational from both a scientific and logical position.”

Moore said BC is not following the science on respirators at the moment.

“These respirators are very, very good at protecting individuals. And I think that science really does show that now. So we’d just like to encourage everyone to engage with that science—and we are seeing that, you know, we’ve seen the World Health Organization, we’ve seen PHAC and Theresa Tam, come up and say that these are very effective,” he said.

“However, we’re only starting to get there now in the conversation in BC.”

Should you make the switch to N95?

While Vitacore’s primary customers are the province and public health authorities across Canada, Moore said it’s been receiving more and more interest from the public since the Omicron wave began.

While employers supplying respirators to their staff will typically require stringent fit tests (particularly in healthcare), Moore said there’s an easy way to test the fit of your own N95 or N99. Put the respirator on and cup your hands around it, then breathe in and out very quickly. Moore said if the respirator moves with your breath, it’s a good fit.

N95 masks are what Rogak wears on public transit, what he recommends to his friends and family, and what he’d prefer to see his students wearing when he goes back to teaching lectures in person, sometimes to rooms of more than a hundred people.

But that recommendation also depends on the trajectory of the pandemic.

“If we have a very small number of cases a day, I’d be happy to wear a lower-grade mask. My risk would just be lower proportionally. But I think in situations now, where we have very high rates of transmission, the chances of getting Omicron are extremely high,” he said.

“I think that the risks are proportionately higher, and the need to have a better mask is proportionately higher.”

And regardless of risk, Ragok said wearing the best mask available to them is a “logical freedom” that people should be allowed to exercise.

“I don’t think it makes sense to prevent people from wearing N95s.”