In one small study published in Respiratory Physiology and Neurobiology, twenty subjects wearing surgical masks walked on treadmills for one hour. Scientists measured their blood oxygen and carbon dioxide concentrations, respiratory and heart rates, and core temperatures. After that hour, the scientists found no significant change in these measurements.
Masks and face coverings are used to mitigate hazard from the coronavirus by keeping large droplets in. The face coverings are not meant to keep the disease out. They make it safer for other people to be around you, if you have it and don’t know it.
