evidence: Myth: The use of surgical or non-medical masks is dangerous to health because the masks trap exhaled carbon dioxide and reduces oxygen. Facts: As noted, these masks are not designed to cause a tight seal. And the science shows that wearing a mask does not affect our lung function or oxygen levels, or cause a buildup of carbon dioxide. There is also the obvious fact that physicians and other healthcare staff routinely wear masks for extended periods, with no ill effects. Concerns have also been raised about how children may be affected by wearing masks, but studies have found no respiratory impact on children from wearing masks, though mask use may not be recommended for children with certain conditions.