A doctor based in Dublin, Ireland, has debunked the idea that a face mask lowers oxygen levels. In fact, he's shown that even wearing several has no effect.

An intensive care unit doctor in England ran about 22 miles in a mask to show people that face coverings won’t hinder their oxygen levels.

A new study about mask wearing during the coronavirus pandemic found that masks don’t cause a person’s oxygen levels to drop.

A new study suggests that face masks have a negligible negative effect on the levels of carbon dioxide and oxygen that a person breathes.

Makers of medical devices that quickly measure oxygen levels in the blood would have to gather extra data to show that their products work for patients of color.