It’s not just the mask, it’s the humidity created inside the mask that helps protect against severe COVID-19, a recent study by National Institutes of Health (NIH) researchers suggests.
The use of cloth masks has been linked with decreased disease severity, which is surprising considering such masks aren’t good at filtering out the smallest aerosol particles that can reach the lower respiratory tract, the researchers wrote.
They tested 4 types of masks: an N95 respirator, a 3-ply disposable surgical mask, a 2-ply cotton-polyester mask, and a heavy cotton mask. Volunteers breathed into a sealed steel box, and the scientists then measured the humidity level inside it.