Physician Lesley Seymour wears personal protective equipment, including an N95 respirator, during a drive-through COVID-19 vaccine clinic at St. Lawrence College in Kingston in December.Lars Hagberg/The Canadian Press

As the Omicron variant rages across Canada with rising case counts and increased hospitalizations, many are wondering what’s the most effective mask to stop the spread of COVID-19.

A growing chorus of infectious-disease doctors around North America are saying respirators, such as N95s or KN95s, are now needed to be worn in public indoor spaces – especially in locations such as hospitals, nursing homes and schools. Authorities in different provinces, however, are divided over whether it’s necessary for governments to provide people with N95s.

Canada’s top doctor, Chief Public Health Officer Theresa Tam, began advising people in November, 2021, to stop wearing cloth masks and instead use three-ply medical masks or, if possible, N95 masks or similar respirators.

So, which face mask provides the best level of protection against Omicron – N95s, medical masks or cloth masks? What are the most effective face masks for children? Here’s everything we know about Canada’s latest mask guidelines.

What is the most effective mask to stop the spread of the Omicron variant?

As of Dec. 16, 2021, the Public Health Agency of Canada has updated its mask guidance on its website, saying non-medical masks, medical masks and respirators can all be used in the community.

Non-medical masks can help prevent the spread of COVID-19 as long as they fit well, have multiple layers, including at least two layers of breathable tightly woven fabric such as cotton, and an effective middle filter layer.

Respirators – such as N95 and KN95 masks – provide the best level of mask protection even though non-medical masks also help prevent the spread of COVID-19, according to Public Health.

N95 respirators are designed to reduce the risk of inhaling hazardous airborne particles and aerosols, according to the Health Canada website. They provide 95-per-cent protection against exposure to respiratory viruses and bacteria when fit appropriately to the user’s face. They were previously recommended only for health care workers coming into direct contact with infectious patients.

Marianne Levitsky, founding president of Workplace Health Without Borders, recommends looking for an N95 mask that has been approved by the U.S. National Institute for Occupational Safety and Health (NIOSH).

She also says that KN95 masks meet a Chinese filtration standard, KF94 masks meet a Korean filtration standard and FFP2 meet a European standard. Health Canada has given interim authorization to a variety of masks that meet the standards, so checking that a brand is listed on their website is a good way to weed out counterfeits.

Public Health also recommended medical masks or respirators for people “who are at risk of more severe disease or outcomes from COVID-19″ and those “at higher risk of exposure to COVID-19 because of their living situation.”

Though the health agency’s guidance now says: “A respirator worn in the community doesn’t need to have been formally fit-tested.”

Most experts agree, however, that single-layer cloth masks are not effective against the Omicron variant and it’s time to ditch them.

“One thing which is really important to realize is if you have a single-layer cloth mask, ditch it, full stop,” Peter Juni, scientific director of Ontario’s COVID-19 Science Advisory Table, told CTV News.

“The minimum would be a double-layered cloth mask that has been washed before so that it is denser and filters better and really fits well. Even better than that, a medical mask below and the cloth mask on top, and then it depends on your [exposure].”

What are the recommended mask guidelines for children?

Public Health Agency of Canada guidelines state that children under 2 should not wear masks. Babies and toddlers have smaller airways, so breathing through a mask is harder. They’re also likely to touch their face more while wearing a mask, increasing their chance of catching and spreading the virus.

Children older than 5, meanwhile, should wear a mask in the same situations or settings where they’re recommended for adults.

Marianne Levitsky says the most important factors in mask selection, no matter the age, are filtration, fit and function:

  • Filtration: how well does it filter aerosols/particles that may be infectious?
  • Fit: how well does it seal to the user’s face so that contaminated air cannot get around the gaps?
  • Function: how comfortable is it and how easy is it to breathe through?

She recommends that parents who are buying masks for children check whether the brand is listed on the NIOSH or Health Canada websites. Another source is Masks4Canada, which lists the distributors of children’s masks. She also suggests parents pay attention to suppliers’ size guidance, and then, if possible, instruct the child to do a seal check.

Parents across the province have asked for students and staff members to have access in schools to N95, KN95 or equivalent respirators, which experts say offer better protection than other types of face masks.

But both Bonnie Henry, B.C.’s Provincial Health Officer, and Deena Hinshaw, Alberta’s Chief Medical Officer of Health, have said N95 masks are not required in schools.

Ontario, meanwhile, has been more receptive to supplying N95s when in-person classes resume. The Education Ministry there has pledged to ensure the province’s teachers have them. The government said that promised shipments of N95 masks were sent to all school boards and school authorities as of Monday, while some shipments to child-care centres were still to go out this week.

In Vancouver, reusable KN95 respirators were distributed to all students and staff at the beginning of the school year, the Vancouver School Board said in a statement.

Teri Mooring, head of the BC Teachers’ Federation, said she would like to see teachers prioritized for N95 masks, which should be available for use in schools.

“For the length of time students and teachers are in school, we think N95s are appropriate,” she said.

When – and in what settings – should masks be worn?

As of Dec. 22, 2021, the World Health Organization updated its guidance on mask-wearing.

The WHO said masks should be worn “irrespective of vaccination status or history of prior infection.” The organization also recommends that a “well-fitting mask” covering the nose and mouth should be worn by people interacting with individuals who are not members of their household, in a number of settings:

  • Indoor settings where ventilation is known to be poor or not properly maintained, regardless of whether physical distancing of at least one metre can be maintained.
  • Indoor settings that have adequate ventilation, if physical distancing of at least one metre cannot be maintained.
  • Outdoor settings where physical distancing of at least one metre cannot be maintained.

In Canada, the local public-health advice on when you should wear a mask varies by province. They are recommended or required in almost all public settings such as stores, schools, business, workplaces and public transit.

The Public Health Agency of Canada says masks are “strongly recommended in any crowded setting, including settings with vaccination requirements.”

How do you properly wear a mask?

The World Health Organization provides the following guidance on the correct use of masks:

  • Wash hands thoroughly before putting on the mask.
  • Inspect the mask for tears or holes, and do not use a damaged mask.
  • Place the mask carefully, ensuring it covers the mouth and nose, adjust to the nose bridge and tie it securely to minimize any gaps between the face and the mask. If using ear loops, ensure these do not cross over as this widens the gap between the face and the mask.
  • Avoid touching the mask while wearing it. If the mask is accidentally touched, wash hands thoroughly.
  • Wash hands immediately after discarding a mask.
  • Do not reuse single-use masks.
  • Do not share your mask with others.
  • Wash fabric masks in soap or detergent and preferably in hot water (at least 60 C) at least once a day. If it is not possible to wash the masks in hot water, then wash the mask in soap or detergent and room-temperature water, followed by boiling the mask for one minute.

“No matter which type of mask you choose, proper fit is a key factor in its effectiveness” says Public Health Agency of Canada.

The agency’s guidance maintains that a well-fitting mask should be large enough “to completely and comfortably” cover the nose, mouth and chin without gaps and not allow air to escape from edges; fit securely with comfortable ties, bands or ear loops and not require frequent adjustments; maintain its shape after washing and drying (for non-medical masks).

How effective are N95 masks against stopping the spread of COVID-19?

Experts are calling for respirators to become the new masking standard to curb the spread of the Omicron variant.

Virginia Tech engineering professor Linsey Marr, who studies viruses in the air, says respirators such as N95s offer far more protection than a surgical mask – both to the wearer and others around them.

Prof. Marr says the main difference comes down to fit – respirators are designed to form a seal around the face, while medical masks often leave gaps that allow virus particles to seep through.

A growing chorus of infectious-disease doctors around the continent are saying the respirators now need to be worn in public indoor spaces – especially in locations such as hospitals, nursing homes and schools.

Steve Rogak, who has been studying aerosols for almost 40 years and has been lab-testing the efficacy of different mask materials during the pandemic, says N95 masks provide 95-per-cent protection or better, because they’re specifically designed to form a good seal on a wearer’s face and filter mist-like particles, including the ones researchers believe are carrying the virus from person to person.

Are N95 masks reusable and how do I clean them?

An American Journal of Infection Control study has found that N95 respirators can be safely reused after decontamination up to 25 times. Researchers found that the devices maintained their function and effectiveness on human subjects with up to 25 cycles of re-use.

Abraar Karan, an infectious-disease doctor at Stanford University who treats several COVID-19 patients a day, says a 10-pack of N95 respirators could be stretched to last more than three months for the average person. A person could wear a different one each day of the week and get up to 10 days out of each N95, he estimated.

The National Center for Biotechnology Information said a N95 or KN95 mask can be cleaned by steaming it in a microwave. Place 60 millilitres of water in a glass bowl, cover it with mesh such as a fruit or veggie produce bag and microwave for three minutes.

Can you double-up on wearing two masks for better protection against COVID-19?

Last November, Dr. Tam, Canada’s Chief Public Health Officer, recommended during her bi-weekly pandemic briefing in Ottawa that Canadians wear three-layer non-medical masks with a filter layer to prevent the spread of COVID-19.

Anthony Fauci, the United States’ top doctor, told NBC in February, 2021, that double-masking could increase the level of protection from COVID-19 and its variants.

“If you have a physical covering with one layer, you put another layer on, it just makes common sense that it likely would be more effective, and that’s the reason why you see people either double masking or doing a version of an N95,” said Dr. Fauci.

Dr. Rogak, the aerosols researcher, also told The Globe and Mail that he estimates his earlier approach to covering his face, using two of the omnipresent blue masks layered one on top of the other, prevented him from breathing in up to 80 per cent of the virus circulating in the air around him. But N95 masks, he estimates, provide 95-per-cent protection or better.


More reading:

Experts call for N-95 masks to become the standard to curb Omicron

As calls for better masking practices increase, provinces are divided over the use of N95s

Surge in COVID-19 cases reignites calls for better masks for health and education workers

Parents in B.C., Alberta anxious as schools set to reopen amid COVID-19 surge

Omicron symptoms mirror the flu and common cold. What should I do if I feel sick?

Everything you need to know about rapid tests, and where to get your hands on them across the country


With files from Mike Hager, Xiao Xu and The Canadian Press.


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