CDC: two masks better than one in fight against COVID-19

Wearing two masks at once can offer more protection against potential coronavirus transmission and exposure than donning a single mask, the U.S. Centers for Disease Control and Prevention (CDC) has advised.

"Double masking" - placing a tight-fitting cloth mask over a thin surgical mask - blocks 92.5% of potentially infectious particles from escaping an infected person, new data from the CDC show. That's more than double the protection a plain surgical mask offers, blocking only around 42% of particles.

And it's even better if everyone double masks. If you come across an infected person and you're both wearing two masks, your exposure to potentially infectious aerosols is reduced by 96.4%.

The CDC is not changing its guidelines officially, but says the study highlights what it already advises, CNN reported.

The CDC tested two simple modifications to improve the performance of commonly used masks by "double masking" and "knotting," which involved folding mask edges inward and knotting ear loop strings to flatten excess fabric and reduce gaps on either side of the face.

A knotted medical mask can block 63% of particles that could contain coronavirus from escaping, up from the usual 42%, and when both an infected and uninfected person knot and tuck their masks, the cumulative exposure is reduced by 95.9%, the CDC found.