Child wearing face-mask; is it safe?
Child wearing face-mask; is it safe? iStock

A new study conducted by researchers from a number of Italian universities strongly suggests that wearing face masks (either surgical or respirator-type) for extended periods of time exposes wearers to dangerous levels of carbon dioxide (CO2).

The study's results are particularly relevant to school-age children who are, in some parts of the world, forced to wear masks for long hours, as carbon dioxide levels in mask-wearers were shown to be significantly higher in people under the age of 18.

Baseline levels of inhaled CO2 without a mask for healthy adults are around 458 ppm. After wearing a surgical mask for just a few minutes during the trial, without any physical exertion whatsoever, levels rose to an average of 4965 ppm, and among minors, the levels were significantly higher at 6439 ppm.

Levels for those wearing FFP2 respirators were around double those of surgical masks - around 9396 ppm.

International standards define 5000 ppm as the maximum acceptable level of exposure for lengthy periods (an average of eight hours, but less in cases of physical exertion). In the study, the CO2 levels for 40.2 percent of volunteers were found to exceed this level when wearing surgical masks. 99.0 percent of those wearing respirators had a level of inhaled CO2 that exceeded 5000 ppm.

Furthermore, as respiratory rates increased in response to even minor physical exertion (an increase from 15 breaths per minute to 18 breaths), the level of inhaled CO2 increased significantly.

The researchers noted severe flaws in previous studies that appeared to show no evident harms resulting from mask wearing, and described the methods they used to overcome these flaws.

They concluded that, "Current guidelines on mask-wearing could be updated to integrate recommendations for slow breathing and a more targeted use," and also observed that, "recent evidence suggests that ... two air-changes per hour may lower aerosol build-up more efficiently than the best-performing masks."