Video Presents Flawed Test on Masks, Oxygen Levels - FactCheck.org

A viral video questions the safety of face masks by using a gas detector to purportedly show that masks result in dangerous oxygen levels for the wearer. But experts — and the company that makes the gas detector — say the video’s test is scientifically flawed. https://www.factcheck.org/2020/07/video-presents-flawed-test-on-masks-oxygen-levels/