Claim that masks trap dangerous levels of carbon dioxide is false

The U.S. Centers for Disease Control and Prevention (CDC) recommends to wear a mask indoors to "reduce the spread of SARS-CoV-2, including alpha and delta variants, among adults and children." Several studies have proven the effectiveness of masks in limiting the spread of the virus that causes COVID-19. (Read more on the latest studies on the CDC site, and read about evidence in this perspective on the PNAS site). However, this hasn't stopped people from claiming that masks are hurting children that are forced to wear them in schools.

A video posted on Facebook and shared widely shows a woman breathing directly onto a carbon dioxide monitor while wearing a cloth mask (used widely for slowing the spread of COVID-19), claiming that the readings show dangerous levels of carbon dioxide. The woman suggests that masks mandates put children in danger. After stating that over 5,000ppm of carbon dioxide can lead to headaches, drowsiness, anoxia, cerebral injury, coma and even death, the device starts beeping after being placed in the mask for around twenty seconds and presents a reading of 1,895, before rising to 10,000. “This is dangerous,” the woman says. We rate this claim as false. Masks or unmasked, breathing directly into a carbon dioxide detector would show the same high levels, since the device is reading exhaled levels, not inhaled levels. Wearing a mask does not raise the carbon dioxide (CO2) level in the air you breathe, according to the Centers for Disease Control and Protection.

As reported by Reuters...

The device used in the video is measuring exhaled - rather than inhaled - air. Breathing directly onto a monitor, with or without a mask on, will produce a high result. This exhaled air, which contains CO2, does not accumulate in cloth masks because the molecules pass through the material with the air.

Findings published in the American Journal of Infection Control (AJIC) on December 16th, 2021, provide guidance for increasing the effectiveness of face masks to reduce the spread of respiratory infectious pathogens including SARS-CoV-2. Read more here.