Partly false claim: Continually wearing a mask causes hypercapnia

Social media users have been sharing an image online and claiming that “continually” wearing a mask causes hypercapnia, due to breathing in exhaled carbon dioxide (CO2). 

Reuters Fact Check. REUTERS/Axel Schmidt

Examples can be seen  here , and  here  .​ 

The claim lists different percentages of CO2 in air, and the symptoms associated with inhaling each. The claim does not clarify what is meant by wearing a mask “continually”, and whether this suggests a certain number of hours at a time or entire days. It also does not specify the type of mask. 

Hypercapnia is a condition arising from too much carbon dioxide in the blood. Mild symptoms include dizziness, drowsiness, fatigue, headache, shortness of breath and disorientation. Severe symptoms include seizures, muscle twitching, loss of consciousness and coma. There are preexisting health conditions that may cause hypercapnia. Some of these include chronic obstructive pulmonary disease and sleep apnea ( here ).​ 

While breathing in excessive amounts of CO2 for large amounts of time can be dangerous, it is unlikely that the general public would suffer from these complications by wearing a mask. Most people would wear face coverings on short stints outside their home as a complementary measure to social isolation ( here ).  

A representative from the U.S. Centers for Disease Control and Prevention (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. You might get a headache but you most likely [would] not suffer the symptoms observed at much higher levels of CO2. The mask can become uncomfortable for a variety of reasons including a sensitivity to CO2 and the person will be motivated to remove the mask. It is unlikely that wearing a mask will cause hypercapnia.”

The claim does not say if hypercapnia will affect health workers or the general public. For the general public, increased CO2 due to wearing masks would be less likely to cause complications like hypercapnia than to a health worker, who wear masks for longer stints. 

A small study in 2006 looked at healthcare workers wearing N95 masks during the SARS epidemic. It concluded that the use of N95 masks may cause the healthcare workers to develop headaches and wearing them for shorter amounts of time may reduce the frequency and severity of the headaches ( here ).


Partly false. Toxic levels of CO2 are dangerous but it is unlikely that wearing a face mask will cause hypercapnia.

This article was produced by the Reuters Fact Check team. Read more about our work to fact-check social media posts here