Do masks lower your oxygen levels? Answers to your questions on COVID-19


We’re breaking down what you need to know about the pandemic. Send us your questions by e-mail at [email protected] and we will reply to you as much as possible. We will post a selection of answers each weekday on our website, and we will also pose some of your questions to the on-air experts during The National and on CBC News Network. So far, we have received over 48,000 emails from across the country.

Do masks lower your oxygen levels?

From big cities to small towns – and throughout the province of Quebec – more and more places in Canada are making masks mandatory in indoor public spaces to help curb the spread of the coronavirus that causes COVID-19.

The new rules have created some challenges, including anti-mask groups and people are spreading false information about wearing the mask. This confuses some Canadians who wonder if there is some truth behind certain claims. Sharon P., for example, worries that a mask will reduce her oxygen levels.

Experts we spoke to said there was no truth to this claim.

“I haven’t seen any medical or scientific evidence to show that wearing a mask depletes your body of oxygen,” said Dr. Susy Hota, medical director of infection prevention and control at the University Health Network in Toronto.

They also don’t let harmful gases, such as carbon dioxide, accumulate, she said.

So you may feel warm or become more aware of your breathing, but “it’s not dangerous,” she says.

Dr. Jennifer Kwan, a family doctor in Burlington, Ontario, agreed.

Oxygen and carbon dioxide still pass through your mask, but it catches the droplets that contain the virus, “which helps reduce transmission,” she said.

“As a healthcare professional, we wear masks in our daily practice and this has not caused any harm to doctors, nurses or surgeons. ”

The real risk, Kwan said, is wearing your mask incorrectly, including sharing it with others, reusing non-reusable masks, or not cleaning cloth masks properly.

WATCH | How to wear a mask correctly:

A face mask is believed to limit the spread of COVID-19. But if it slips under your nose, hovers around your chin, or if you touch the outside with your hands, medical experts say it could be riskier than not wearing it at all. 3:55

“It is very important, with the increase in the wearing of masks, to teach people how to wear them properly,” she said.


  • Wash or disinfect hands before putting them on and taking them off.
  • Handling only by ear straps. Don’t touch the front.
  • Keep your face covered from the top of your nostrils to the bottom of your chin.

We’ve covered the most frequently asked questions about masks, including the best types of fabrics, filters, and if facial hair is a problem, including a previous FAQ.

Is it safe to wear masks with vents?

You might see people on the street with masks that have valves or vents designed to make breathing easier.

Jill F. wonders if these masks are effective in stopping the spread of the coronavirus.

The answer is no.

WATCH | The truth about the valves of facial masks:

A pulmonologist answers viewers’ questions about the COVID-19 pandemic, especially if masks with respiratory valves make them less effective. 3:39

A ventilated mask may seem high tech and more comfortable to wear, but Health Canada says it allows infectious respiratory droplets to asked Canadians not to use them to prevent the spread of the coronavirus.

“The benefit we see from masks often is that they protect others from you,” explained infectious disease specialist Dr. Sumon Chakrabarti.

“So if you have a vent there and you have COVID-19… you will be pushing these particles out, so that defeats the purpose of the mask.

There are masks that appear to have a valve, but instead it’s just a piece of plastic lying on the fabric. Kwan says that these false openings are just for “cosmetic purposes” and do not compromise the function of the mask, as long as there is tissue behind it.

So skip the ventilated and valve masks. Chakrabarti and Kwan recommend surgical or homemade masks instead.

And remember: wearing a mask alone will not prevent the spread of COVID-19; it is not a substitute for physical distance and good hand hygiene.

Where are we in the pandemic?

Many provinces relaxed restrictions after the number of COVID-19 cases started to decline, but are now experiencing a resurgence. This has many Canadians, including Tom L., wondering what stage of the pandemic we are at.

The country is still technically in the first wave, experts say.

For the first wave to end, we would have to reach a point where we see “virtually no” new cases, said Dr. Christopher Labos, epidemiologist, cardiologist and associate at the Office of Science and Society of McGill University. . Any subsequent influx will signal the start of a potential second wave.

This means that a second wave is not the same as a second peak.

« [A second wave] needs to be differentiated from a second peak, which is in the first wave when cases can go up and down – and go up, “said Labs.

Despite significant declines, Ontario and Quebec have failed to get rid of the virus entirely, and Alberta has seen a slight increase.

“If the number of cases starts to rise again… technically it wouldn’t be a second wave, it would be a second peak in the first wave because we’ve never seen a case go down to zero,” Labs said. .

It is not certain that Canada will see a second wave. Some experts say it’s preventable, as long as we keep abreast of small outbreaks that will occur in the near future.

“If we jump on it quickly and have the capacity to do the early identifications, contact tracing and isolation, we can overcome this without a second wave,” said infectious disease specialist Dr Isaac Bogoch. and scientist at the Toronto General Hospital.

“But if we don’t, if we let our guard down, well, it comes. “

Last week, we answered questions about the making of your nails.

Keep asking your questions by writing to us at [email protected]


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