Another air quality monitor demonstration fails to show masks reduce oxygen

A viral video uses a demonstration with a child to claim that the cloth masks used to fight the spread of COVID-19 are unsafe for children.

It’s a new version of a claim that’s been debunked.

"People make the same mistakes each time, and the results don't measure what they would like to measure," said biology professor Benjamin Neuman, chief virologist at Texas A&M University’s Global Health Research Complex, said about demonstrations that use air quality monitors. "This demonstration uses the wrong equipment to test the wrong parameter, so it's not surprising that the result is nonsense."

The video was shared on TikTok and in a Facebook post. The Facebook post was flagged as part of Facebook’s efforts to combat false news and misinformation on its News Feed. (Read more about our partnership with Facebook.)

The video is labeled as being from a meeting of the school board in Lago Vista, Texas, about 35 miles northwest of Austin. The board held a special meeting on Aug. 23 on its "safe return to in-person instruction" plan.

In the video, a man who said he was doing the demonstration with his daughter, an elementary school student, instructs the girl to put on a simple cloth face mask and then he holds a device next to her for a few seconds. The video is taken from a distance, so it’s not clear exactly what the device is, but the man describes it as an air quality monitor like one he would use to measure air quality in confined spaces when working in construction. He said that when applying it to measure the air quality inside his daughter’s mask, the monitor showed the air had an oxygen level of "19.5 parts per million," which he said was dangerous. He asked that children not be forced to wear masks in school.

A similar demonstration, but said to be measuring carbon dioxide parts per million, was shown in a video posted on Facebook from a school board meeting Aug. 9 in Conway, N.H.

The air we breathe is made up of about 78% nitrogen by volume, 21% oxygen and much smaller amounts of argon, carbon dioxide, hydrogen and other gases. 

In the video, the man apparently alludes to the federal Occupational Safety and Health Administration, which regulates workplaces. OSHA defines an atmosphere that is less than 19.5% oxygen as oxygen-deficient, and potentially unsafe. So the reference to "19.5 parts per million" in the video misstates the safety threshold. That unit of measurement is typically used to describe the concentration of chemical contaminants in water or soil, or trace amounts of a gas; 19.5 ppm is not a plausible reading of oxygen concentration in the atmosphere at a school board meeting. 

The other flaw in the demonstration, Neuman explained, is in how the meter is used to generate a reading for oxygen intake.  

"This test does not tell the difference between exhaled air, which is high in carbon dioxide, from inhaled air, which is low in carbon dioxide, because the monitor is under the mask where the child is both inhaling and exhaling," Neuman said. "Holding a meter up to exhaled air would give the result shown. But the mask is porous, and most of the air for each new breath comes in through the mask."

Kirsten Koehler, an environmental health and engineering professor at the Johns Hopkins University Bloomberg School of Public Health, said exhaled breath is only about 16% oxygen, because the body is taking in oxygen and exhaling carbon dioxide. 

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"When you breathe through the mask, some small volume of air will be left in the mask with this lower concentration at the end of an exhalation. As you inhale, that air is rapidly replaced with fresh air from the room filling your lungs with air at normal oxygen conditions," she said. The sensors on the air quality meter "cannot respond instantaneously to changes in concentration."

A more accurate way to assess the effect of a mask on oxygen flow is to analyze a blood sample, Neuman said. Or, "a reasonable do-it-yourself test would be to wear a pulse oximeter while wearing a mask or not wearing a mask for longer periods of time, perhaps half an hour each, and then compare oxygen saturation levels." The test would have to be repeated several times to get an accurate reading.

"Fortunately, this work has already been done quite carefully in several papers, which demonstrated no significant drop in oxygen content or rise in carbon dioxide content when wearing a mask," Neuman said.

Some experts have argued against mask mandates for children in schools. In a Wall Street Journal opinion article, Dr. Marty Makary, professor at the Johns Hopkins School of Medicine, and Dr. H. Cody Meissner, chief of pediatric infectious diseases at Tufts Children’s Hospital, said masks make it more difficult for some children to learn, and may have negative physical and developmental effects. 

"Any child who wants to wear a mask should be free to do so. But forcing them to make personal, health and developmental sacrifices for the sake of adults who refuse to get immunized is abusive," the doctors wrote. "Before we order the masking of 56 million Americans who are too young to vote and don’t have a lobby, let’s see data showing the benefits and weigh them against the long-term harm."

Research suggests it’s possible that masks could spur social isolation and impede communication, especially for people who are deaf or have trouble hearing. But scientists have found little evidence that the cloth masks worn by most students negatively affect oxygen or carbon dioxide levels.

We have previously found concerns about masks and oxygen or carbon dioxide levels to be oversold, as have other fact-checkers.  

Studies specific to children have been rare, so most of the scientific literature has involved research on adults. Two studies on children used N95 masks, but even these found no significant impacts on breathing. Other peer-reviewed studies of adults have produced similar results.

N95 respirators are hospital-quality masks with a tighter seal and better filtration than ordinary cloth masks and they provide more protection from COVID-19.

One paper published in February 2021 looked at 10 previous studies of adults or children that addressed questions of breathing while wearing a mask. The authors expressed disappointment at how few studies looked specifically at the impacts on children, but the paper found little reason for worry. 

"The eight adult studies, including four prompted by the pandemic and one on surgeons, reported that face masks commonly used during the pandemic did not impair gas exchange during rest or mild exercise," the authors wrote.

A viral video claimed that a demonstration with an air quality monitor showed that cloth masks reduce oxygen levels and are unsafe for children.

It’s a new version of a claim that has been repeatedly debunked. The demonstration does not measure what it claims to measure, and studies have repeatedly found that cloth masks do not unsafely reduce oxygen levels.

We rate the claim False.