Study: Masks Are Not Linked to Carbon Dioxide Over-Exposure

older woman wearing a surgical mask outsdie


fabio camandona / Getty Images

Key Takeaways

  • Wearing a mask will not lead to carbon dioxide poisoning, even in individuals with lung disease.
  • Breathlessness while wearing a mask may simply be related to increased activity or temperature, or general discomfort.
  • Mask-wearing is necessary in order to curb the continued increase in COVID-19 cases.
  • There are many different types of masks ranging from cloth masks to plastic shields, all of which considered to be safe and protective.

Wearing a face mask does not lead to carbon dioxide poisoning despite some people’s belief face coverings are a health risk, a new study finds.

Researchers behind the October study, published in the Annals of the American Thoracic Society, set out to determine whether or not there is a link between wearing a face mask and issues with gas exchange, which involves changes in oxygen or carbon dioxide levels. The researchers assessed both healthy individuals and veterans with severe chronic obstructive pulmonary disease, or COPD, before and after using surgical masks. People with COPD "must work harder to breathe, which can lead to shortness of breath and/or feeling tired,” according to an American Thoracic Society fact sheet about the condition.

“Public mask use has been heavily politicized with inconsistent recommendations by authorities leading to divided public opinion,” Michael Campos, MD, and the study’s co-authors wrote. “Another reason commonly argued against mask use involves safety concerns, as mask discomfort has been attributed to rebreathing CO2 and hypoxemia, with some even considering that masks are lethal.”

But the effects of wearing a mask are “minimal at most” even in people with very severe lung impairment,” Campos said in a news release.

Researchers launched the study after reports of a public hearing in Palm Beach, Florida, during which people made comments about masks, including that wearing them was putting lives at risk.

Campos noted that, while the study may be limited in sample size, it was clear there was “nil effect” of mask-wearing on gas exchange. He added: “The public should not believe that masks kill.”

What This Means For You

While mask-wearing might sometimes feel uncomfortable, it does not pose a health risk. If you feel breathless while wearing a mask, step outside and/or away from people to remove your mask and take a break.

Why Were Masks Linked to CO2 Poisoning In the First Place?

In addition to the aforementioned politicization and general misinformation surrounding masks, the researchers said people began linking mask-wearing and carbon dioxide poisoning to a general feeling of breathlessness they felt while wearing a mask. But Campos said dyspnea, or the feeling of shortness of breath, is not linked to changes in oxygen or carbon dioxide levels while wearing a mask.

“It likely occurs from restriction of airflow with the mask in particular when higher ventilation is needed (on exertion),” he said in the news release. “If you’re walking briskly up an incline, for example, you may experience feelings of breathlessness.” 

Campos said a too-tight mask may also increase the feeling of breathlessness.

“The solution is simply to slow down or remove the mask if you are at a safe distance from other people,” he said.

Need More Proof? 

Further evidence that mask-wearing does not affect gas exchange includes taking into consideration surgeons who wear masks for as long as 12 hours or more, says Leann Poston, MD, of Invigor Medical

“Imagine for a moment, if face masks did change blood levels of carbon dioxide and oxygen levels in the blood,” she says. A surgeon's brain chemistry would be affected. It would affect his or her fine motor skills. “If face masks could even remotely cause this outcome, an alternative would have been invented by now.”

Fahmi Farah, MD,
a Texas-based cardiovascular and internal medicine doctor, agreed, adding: “Masks have been in use by healthcare professionals on a daily basis and they do not impede breathing nor do they cause retention of carbon dioxide. Masks are meant as a protective barrier against harmful pathogens, such as droplets that can contain germs like viruses, bacteria, and mold.”

If math is your thing and you’re looking for some numbers to prove mask-wearing is not a health risk, Poston asks you to consider the following:

  • Coronavirus can be between 60 and 140 nanometers in diameter. Oxygen is 0.120 nanometers, and carbon dioxide is 0.232 nanometers.
  • Respiratory droplets are typically 5000 to 10,000 nanometers in diameter.
  • The filtration pores in a cloth mask are typically between 10 nanometers and 6000 nanometers.

Put simply, “math and physics” verify that face masks cannot stop the flow of respiratory gases, but they can stop respiratory droplets, Poston says.

Can I Just Cover My Mouth With a Mask? 

In short, absolutely not, says Poston. In order to help prevent the spread of COVID-19, you cover your mouth and nose. Consider a recent study in Nature Medicine, which showed that mucus-producing cells in the nose had the highest levels of COVID-19 proteins, further emphasizing why it’s necessary for your face to be covered from the bridge of your nose to your chin.

And as for the rumor that wearing a mask can cause a weakened immune system, it’s just not the case, Poston says.

“Your immune system is exposed to pathogens of all sorts throughout your lifetime,” she says. “Wearing a mask to decrease exposure to respiratory pathogens will not have a significant impact on the function of your immune system. Your immune system will remain very busy fighting all of the pathogens it is exposed to in your daily life. None of us lives in a sterile environment!”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Samannan R, Holt G, Calderon-Candelario R, Mirsaeidi M, Campos M. Effect of face masks on gas exchange in healthy persons and patients with COPD. Annals of the American Thoracic Society.

  2. Lareau SC, Fahy B. Patient education: Information series: Chronic obstructive pulmonary disease (COPD). Am J Respir Crit Care Med. 2019;199:P1-P2.

  3. American Thoracic Society. Face masks unlikely to cause over-exposure to carbon dioxide, even in patients with lung disease. Newswise.

  4. Bar-On YM, Flamholz A, Phillips R, Milo R. SARS-CoV-2 (COVID-19) by the numbersElife. 2020;9:e57309. doi:10.7554/eLife.57309

  5. Konda A, Prakash A, Moss GA, Schmoldt M, Grant GD, Guha S. Aerosol filtration efficiency of common fabrics used in respiratory cloth masks [published correction appears in ACS Nano. 2020 Aug 25;14(8):10742-10743]. ACS Nano. 2020;14(5):6339-6347. doi:10.1021/acsnano.0c03252

  6. Sungnak W, Huang N, Bécavin C. et al. SARS-CoV-2 entry factors are highly expressed in nasal epithelial cells together with innate immune genesNat Med 26, 681–687 (2020). doi:10.1038/s41591-020-0868-6

By Caroline Shannon Karasik
Caroline Shannon Karasik is a writer based in Pittsburgh, PA. In addition to Verywell, her work has appeared in several publications, including Good Housekeeping, Women's Health and Well+Good.