This is how often you should wash your cloth face mask.
The claim: Face masks drastically reduce oxygen intake, cause carbon dioxide toxicity
As states are reopening, health guidelines recommend that people maintain social distancing, practice hand-washing and wear face masks.
The use of face masks is encouraged by the Centers for Disease Control and Prevention and members of the White House’s coronavirus task force to prevent further spread of the coronavirus, especially in places where it is hard to social distance.
Wearing face masks has become controversial — even political in some cases — resulting in misinformation about their effectiveness.
One Facebook post claims that wearing a mask for prolonged periods of time can drastically reduce the wearer’s oxygen levels and result in carbon dioxide toxicity. (The poster said she did not know the origin of the image she shared and did not check to see whether the information was correct.)
Another viral meme featuring three people wearing masks while walking on a beach says face mask wearing “reduces oxygen up to 60%” and “increases risk of CO2 poisoning.”
Face masks 101
According to the FDA, there are two main types of masks, N95 respirators and surgical masks. Both are tested for fluid resistance and filtration efficiency.
- N95 masks are more tightly fitted, making them more likely to inhibit the breathing of the wearer if worn for a prolonged period of time.
- Surgical masks, which are disposable, and other types of cloth face masks are looser fitting, making it highly unlikely that wearers would see significant depletions in their oxygen intake. Non-N95 masks also are porous, allowing air to flow in and out and permitting normal respiratory functions, while limiting the release of respiratory droplets.
It is common for surgeons and other scientists or health care workers to wear face masks, particularly N95 respirators, for prolonged periods of time.
Neither the CDC nor the World Health Organization has issued warnings suggesting the use of surgical face masks would result in dangerous oxygen level depletion within the general public.
The CDC has requested the general public reserve N95 respirator masks for health care workers, but members of the public and other industries do still have access to them.
Despite the N95 mask’s proven filtration effectiveness, research has found that the masks can inhibit the wearer’s breathing if worn for extended periods of time, particularly in cases where the person has an existing respiratory illness.
The CDC does advise that cloth face coverings should not be placed on children younger than 2, those who have trouble breathing or anyone who is unconscious, incapacitated or unable to remove the mask without help.
Will face masks cause hypoxia?
A reduced oxygen intake level may lead to hypoxemia, a condition where there is low arterial oxygen supply, or hypoxia, a condition where the supply of oxygen in tissue is insufficient.
One Facebook post claimed “wearing a mask for an 8 hour shift can reduce your oxygen intake level to a 93 if you have healthy lungs … it is not healthy to have your oxygen level at that.” The post did not specify which type of mask it was referencing.
A healthy oxygen intake level, or the amount of oxygen circulating in your blood, ranges from 95-100%, with anything below 90% considered low, according to Mayo Clinic.
Will a mask give the wearer hypoxia? Simply, no.
“This misinformation may arise from the feeling of lack of air due to mechanical obstruction depending on the type of mouthpiece we are using. But the feeling of obstruction is because we are not used to using the mouth mask. But as such it will not cause us any kind of hypoxia,” Dr. Daniel Pahua Díaz, an academic from the Department of Public Health at the National Autonomous University of Mexico medical school, told Animal Político earlier in May.
Will face masks cause carbon dioxide toxicity?
Carbon dioxide toxicity, or hypercapnia, is a condition that results from too much carbon dioxide in the bloodstream, which can be caused by rebreathing exhaled carbon dioxide.
The same Facebook post claimed face masks “block your exhaling of carbon dioxide and then you breathe it back in … it destroys lung tissue.” The viral meme suggests wearing a mask can increase a wearer’s chance of carbon dioxide poisoning.
As noted, surgical masks are porous, allowing for normal respiratory function. Other cloth face masks typically are even more porous.
It’s important to note that the majority of the time, with health care workers as an exception, the general public is not wearing face masks for prolonged periods of time, meaning a dangerous build-up of CO2 is unlikely.
Additionally, the CDC told Reuters, “The CO2 will slowly build up in the mask over time. However, the level of CO2 likely to build up in the mask is mostly tolerable to people exposed to it … It is unlikely that wearing a mask will cause hypercapnia.”
Poynter notes that the rumor of mask wearing causing hypoxia has circulated the globe for a month or more, and has been fact-checked by several organizations.
The CDC told Snopes that N95 respirators could cause the buildup of carbon dioxide over time, which can also be mitigated by feeding in oxygen or simply taking a break and removing the mask. But the same effects are not likely in people wearing cloth face masks, especially for the brief amount of time they are in public.
Our rating: Partly false
The claims in the post have been rated PARTLY FALSE, based on our research.
There is no evidence to support that the general public — which doesn’t typically wear masks for prolonged periods of time — will experience significant reductions in oxygen intake level, resulting in hypoxemia. While CO2 can build up in face masks, it is unlikely that wearing a mask will cause hypercapnia, according to the CDC
It is true that those who are most at risk of negative effects from face masks have been advised by the CDC to avoid the face coverings and reach out to their health care providers for additional guidance.
Our fact-check sources:
- CDC, recommendation for cloth face covers
- Mayo Clinic, Hypoxemia definition
- Hypoxia and Hypoxemia facts
- FDA, N95 Respirators and Surgical Masks (Face Masks)
- CDC, Cloth Face Coverings: Questions and Answers
- Physiological Impact of the N95 Filtering Facepiece Respirator on Healthcare Workers
- Animal Político, No excuses: It is false that wearing a mask causes hypoxia
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