Fact check: Masks are effective against COVID-19; OSHA doesn't say they offer no protection

Anna Staver, USA TODAY

The claim: Cloth masks will dangerously reduce oxygen levels, and masks don't work

There are a lot of claims circulating on social media about the effectiveness of different kinds of face masks. A viral post that includes a long text purportedly written by someone "OSHA 10&30 certified," sometimes along with an image with writing on a car’s rear window, claims masks can cause brain damage, headaches and high blood pressure by reducing a person’s oxygen intake to dangerous levels. 

Fact check: Ear loop masks – even homemade cloth masks – offer protection against COVID-19

Required oxygen levels

The post claims that the Occupational Safety and Health Administration requires employers to keep oxygen levels in their work environments at a minimum of 19.5%. 

That’s true.

The air we breathe is about 21% oxygen, 78% nitrogen and 1% other gases, including carbon dioxide and neon, according to NASA.

OSHA says in its preamble to a document called the Respiratory Protection Standard that going below 19.5% can cause “increased breathing rates, accelerated heartbeat and impaired thinking,” as well as “impaired attention, thinking, and coordination, even in people who are resting.”

The more detailed part of the claim is more false than true.

Do masks reduce oxygen intake? Are they safe for work?

The post claims wearing a mask puts a person’s oxygen intake below OSHA’s required levels and can cause brain damage, high blood pressure and headaches.

USA TODAY fact checked whether masks can cause such afflictions and found that cloth and surgical masks are unlikely to cause a dangerous drop in oxygen intake because they are not tight-fitting.

Kelli Randell, an internist and medical adviser at Aeroflow Healthcare, told Health.com that using any mask for a long time has not been shown to cause carbon dioxide to build to a toxic level in otherwise healthy people.

Does OSHA say anything about the dangers of wearing a mask at work?

Yes. OSHA says on its COVID-19 FAQ webpage that masks may not be appropriate for certain workers. “For example, cloth face coverings could become contaminated with chemicals used in the work environment, causing workers to inhale the chemicals that collect on the face covering,” according to OSHA. 

The agency recommends alternative protections such as clear face shields. OSHA says on its website that cloth masks cannot not be used as substitutes for required personal protective equipment.

Airline mask requirements: Check the policies for North American carriers

Other mask safety claims

The image of the car with writing on it accompanied a long post that made several claims about face masks and were purported to come from a person who was “OSHA 10&30 certified.” That means a person took OSHA’s 10-hour and 30-hour training on general health and safety hazards. This training does not cover COVID-19 topics, according to OSHA. The agency doesn’t certify people who take such training. 

Fact check: No, N95 filters are not too large to stop COVID-19 particles

The post claims that N95 masks are not safe to wear in public because they filter only the air coming in, not the air going out. This is true but only for the kind of N95 masks commonly used in construction. These have valves, but medical N95 masks do not. In May, the San Francisco Department of Public Health shared side-by-side images of medical and construction N95 masks and urged residents not to use the kind with valves.

The post's writer says surgical masks were “designed and approved for sterile environments,” and they clog quickly out in the real world, essentially rendering them “useless” after 20-30 minutes.

Completed face masks are packaged for shipping at the Tom Bihn factory in Seattle in March. Tom Bihn is a travel bag company that shifted production to face masks because of the COVID-19 outbreak.

"The surgical mask is not designed for the outside world and will not filter the virus upon inhaling through it. Its filtration works on the exhale (just like a vacuum bag, it only works one way)," the post says.

OSHA says surgical masks don’t protect “against airborne transmissible infectious agents due to loose fit and lack of seal,” but they can “contain the wearer's respiratory droplets.” Basically, the masks are meant to protect others. 

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The FDA says surgical masks do stop the wearer from inhaling large particles: "If worn properly, a surgical mask is meant to help block large-particle droplets, splashes, sprays, or splatter that may contain germs (viruses and bacteria), keeping it from reaching your mouth and nose."

OSHA recommends surgical masks for dentists and other medical professionals who don’t work in sterile environments, but it doesn’t say how long the masks last. OSHA recommends surgical masks “be properly disposed of after use.”

The Centers for Disease Control and Prevention asks the general public to wear cloth masks, not "use a face mask meant for a health care worker.”

"The cloth face coverings recommended are not surgical masks or N95 respirators.  Those are critical supplies that must continue to be reserved for health care workers and other medical first responders, as recommended by current CDC guidance," the CDC's website says.

The post claims that cloth masks trap carbon dioxide and “the moisture caught in these masks can become mildew-ridden overnight.”

"Cloth masks are WORSE than none," it says. That is false.

Much like surgical masks, cloth face coverings are loose-fitting and meant to protect others more than the wearer from infection.

"Cloth face coverings may slow the spread of the virus and help people who may have the virus and do not know it from transmitting it to others," the CDC says on its website.

A CDC representative told Reuters, “CO2 will slowly build up in the mask over time,” but the levels are “mostly tolerable to people exposed to it.”

Symptoms could include a headache, but Reuters reported “it is unlikely that wearing a mask will cause hypercapnia,” or excessive carbon dioxide buildup in the bloodstream.

Fact check: Wearing a face mask will not cause hypoxia, hypoxemia or hypercapnia

The CDC says, “Cloth face coverings should not be placed on young children under age 2, anyone who has trouble breathing, or is unconscious, incapacitated or otherwise unable to remove the mask without assistance.” 

The CDC and OSHA recommend laundering cloth masks after each use. 

Our rating: Partly false

Both the picture and the post are PARTLY FALSE, based on our research. It is true that OSHA requires employers to keep their environment's air at 19.5% oxygen or higher. And it is true that surgical masks keep the wearer's droplets from getting into the air but do not protect the wearer from inhaling particles.

It is false that mask-wearing will cause serious health effects; cloth and surgical masks are unlikely to cause a dangerous drop in oxygen intake because they are not tight-fitting. The sweeping claim about the safety of N95 masks is not true. And it is false to say "cloth masks do not filter anything." Cloth masks can help prevent the wearer from spreading the virus to others.

Our fact-check sources:

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This article originally appeared on USA TODAY: Fact check: OSHA didn't say masks offer no COVID-19 protection