Should you wear a mask? Advice for navigating a mask-optional Canada

With masks now optional in most public spaces and Quebec recently joining the rest of Canada in relaxing its rules, the mental gymnastics required to figure out whether or not masking is necessary might feel tantamount to performing advanced calculus.

Yet even as the rules shift for where masks are required, some people may still choose to wear them — as they did before mandates came into effect.

To help Canadians evaluate what's best for their own health and the health of their loved ones, CBC News asked experts who study airborne particles to weigh in about when, where and for whom masking is still recommended.

Will a mask work if I'm the only person wearing one? 

The message from public health officials for much of the pandemic was that masks work best if everyone wears them.

But if you want to protect yourself in an indoor public space where many people will be unmasked, a KN95 or higher offers good protection, according to University of British Columbia mechanical engineering professor Steve Rogak.

Rogak, who is based in Vancouver, studies all kinds of aerosols and has been testing the efficacy of different mask materials during the pandemic.

"If you have an N95 mask … and you can tell that it's not leaking around the edges and it's nice and snug, I would say that's extremely good protection."

"It's going to capture much more than 90 per cent of the virus, probably more than 99 per cent," Rogak said.

While an N95 is generally considered the gold-standard of masks and is often used by health-care workers, the material on a KN95 mask is also very effective, Rogak said.

KN95s are the Chinese equivalent of N95s, and Rogak said they will capture around 90 per cent of virus particles as long as they fit well.

Both Rogak and Parisa Ariya, the director of the Atmospheric and Interfacial Chemistry Laboratories at Montreal's McGill University, agreed that mandates being lifted doesn't mean the virus has disappeared.

"We should not close our eyes and believe that everything is gone," said Ariya, who researches the ways in which airborne viruses spread and is a leading expert in the study of bioaerosol transmission.

She compared virus particles to a computer software algorithm — even if you can't see it with the naked eye, it still exists and works.

"Viruses are physical entities. Physical bodies. And the mask idea — it's nothing new — it avoids and decreases transmission."

Who should consider wearing a mask? 

Many public health agencies are still recommending that Canadians wear masks in indoor public spaces, especially those at higher risk of having severe outcomes from COVID-19.

In fact, the Public Health Agency of Canada's current guidance is that everyone keep masking.

"We recommend that you wear a mask in public indoor settings," the agency's website states.

"You should feel free to wear a mask even if it's not required in your community or setting. This is an appropriate personal decision."

Most provincial public health authorities emphasize that older people should continue to wear masks, as well as those with certain medical conditions, and people who are pregnant or have recently given birth. Alberta recommends people at risk of severe outcomes wear medical masks, and Ontario's chief medical officer of health strongly recommends everyone wear masks in indoor public settings.

Quebec's interim public health director, Dr. Luc Boileau, recently said anyone with COVID symptoms, whether or not they've tested positive, should mask up because "you don't need to be sure that it's COVID" to be prudent.

Where should people consider wearing a mask? 

In most provinces, masks are still required in health-care settings and other indoor spaces with vulnerable populations, such as long-term care homes. Some regions, including Alberta, Quebec and Ontario, still require masks on public transit.

Ariya said regardless of what the rules are, she prefers to wear a mask indoors, especially if the space is crowded with strangers.

"When I take the metro, I wear my mask. Is it something that I like to do? Absolutely not, particularly in the summer. But it is about respect," she said.

"When you are more susceptible, or you have a grandmother or mother or family [members] who are immunocompromised, I would wear one. I don't think it's too much to do for a loved one."

Rogak agrees and said that personally, he prefers to wear a well-fitted mask any time he's indoors with a lot of strangers.

"I am comfortable going through a sparsely populated room that's got one or two people at the end — the chances of getting it are very slim," he said.

"But if you're going to be stuck in a crowded room for half an hour or an hour with five or six other people, people you don't know, then I'm not comfortable [without a mask]."

Rogak said without mandatory restrictions in place, it's now up to Canadians to take responsibility for their choices.

To help people make informed decisions based on COVID-19 trends, the Public Health Agency of Canada recently launched a new online COVID-19 wastewater surveillance dashboard.

The tool is meant to provide people with the data necessary to help make informed decisions going forward.

"The risks haven't changed overnight just because the mask mandate goes away," Rogak said.

WATCH | Masks coming off but COVID-19 not done, doctor says