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Mask Myths: Does a Mask Limit My Oxygen Intake?

Woman wearing masks in different scenarios 

Posted July 16, 2020 

Gill Allen, MD, a pulmonologist and critical care physician at the University of Vermont Medical Center and professor at the University of Vermont Larner College of Medicine, dispels some myths and answers popular questions about the efficacy of face mas​ks.

How does someone’s age, weight, fitness or underlying health condition affect their ability to wear a mask?

A: Everyone can wear a mask safely, and while it’s not always comfortable, it is important to do so to protect others from the spread of COVID-19. People with underlying respiratory conditions, like severe asthma or COPD, might find it harder to breathe because of the added resistance to flow.

Additionally, people of advanced age or weight do lose lung function and may find it more difficult to breathe with a mask on, but for most, it will not impair oxygenation (oxygen getting into the blood) or ventilation (blowing of carbon dioxide). Health care professionals have worn masks for decades, often uninterrupted for hours, in operating rooms without adverse effects. If you are unsure about your oxygen capacity speak to your health care provider.

Should I wear a mask while exercising indoors/outdoors?

A: If you are exercising outdoors, like biking or running, and not within 6 feet of others, it’s okay to not wear a mask – keep one with you in case you come into close contact with others, though. There are some studies from Europe showing that the vapor trail of a runner extends well beyond 6 feet behind them, and it is probably better to distance much farther from another runner or walker.

The data is less clear about group sports however. It’s likely that outdoor group sports are safer than indoor group sports, due to wind and superior ventilation/air exchange, but I personally feel that the risk of human-to-human spread in outdoor sports is currently unacceptably high, and would recommend against them. People are hyperventilating and running in and out of one another’s vapor trails in soccer and basketball, perhaps less in baseball. The CDC currently recommends against group sports. https://www.cdc.gov/coronavirus/2019-ncov/community/schools-childcare/youth-sports.html

The COVID-19 virus is 0.125 microns and N95 masks only filter down to 0.3 microns so how can N95, surgical or cloth masks be effective?

A: While the size of the virus itself is very small, the virus particles do not travel through the air alone. The virus needs to hitch a ride on the tiny droplets of saliva and water that are exhaled when someone coughs or sneezes, or even on dust particles. Shouting or singing can also disperse these droplets widely. If you are infected with COVID-19, you likely contracted the virus from inhaling viral-infected particles. It is also not true that N95 masks do not filter particles smaller than 0.3 microns, they can and do. There are multiple layers of fibers that carry an electrostatic charge that helps entrap these smaller particles.

While there have not been large-scale controlled trials, recent research shared in the Journal of Aerosol Science shows that masks protect people surrounding the mask-wearer. This research indicates that masks are effective at trapping exhaled air and respiratory droplets in the mask and successfully limit the number and movement of viral particles on droplets in the air. We can also  draw some conclusions by inference from data demonstrating decreases in viral transmission within States where universal masking has been mandated.

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