Claim: Masks limit oxygen intake and increase carbon dioxide (CO2), and they increase the potential risk of CO2 poisoning
One small study looked at 39 volunteers who had end stage renal disease and received dialysis during the SARS pandemic in 2003. The researchers found that 70% of participants who wore an N95 respirator for 4 hours during treatment experienced a fall in oxygen levels.
Another study found no differences in the oxygen levels in 10 intensive care nurses who wore N95 respirators for their shifts.
Carbon dioxide poisoning is very rare, and experts mostly associate it with accidents that occur in confined spaces, such as ships and mines.
Hypercapnia, or hypercarbia, occurs when a person has too much carbon dioxide in their blood. Hyperventilation and some lung conditions can lead to hypercapnia. It can manifest as dizziness and headaches at the mild end of the spectrum, and confusion, seizures, and coma at the severe end.
Research from 2006 found that during the SARS pandemic in 2003, healthcare workers who wore N95 respirators for more than 4 hours at a time were more likely to develop headaches.
A representative from the CDC recently spoke to Reuters about hypercapnia: “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. […] It is unlikely that wearing a mask will cause hypercapnia.”
Claim: Masks are dangerous for people with certain health conditions (COPD, asthma), as they may restrict breathing
The WHO acknowledge that people living with asthma, chronic respiratory conditions, or breathing problems may experience difficulties when wearing face masks.
The CDC recommend that anyone who has trouble breathing should not wear a face covering.