Double-masking nearly doubles protection against Covid-19

·2-min read

Wearing two face coverings nearly doubles the level of protection from Covid-19 - as long as the masks fit properly.

Earlier this year, experts from the U.S. Centers for Disease Control and Prevention (CDC) recommended people don two masks when out in public in order to curb the chances of picking up the virus.

But while wearing two masks can nearly double the effectiveness of filtering out particles, preventing them from reaching the wearer's nose and mouth and potentially causing Covid-19, researchers have reminded citizens that this method only works if the chosen coverings fit the face well.

"The medical procedure masks are designed to have very good filtration potential based on their material, but the way they fit our faces isn't perfect," said lead author Dr Emily Sickbert-Bennett of University of North Carolina Health Care.

To test the fitted filtration efficiency (FFE), a team of researchers decided to wear a range of masks while exposing themselves to small salt particle aerosols inside of a stainless-steel exposure chamber. Accordingly, they found that a procedure mask without altering the fit is about 40-60 per cent effective at keeping Covid-19-sized particles out. A cloth mask is about 40 per cent effective.

In addition, when a cloth mask is placed over a surgical mask, the FFE improved by about 20 per cent and improved even more with a snug-fitting, sleeve-type mask.

"We've found that wearing two loosely fitted masks will not give you the filtration benefit that one, snug-fitting procedure mask will," Dr Sickbert-Bennett added. "And with the current data supporting how effective mask-wearing is at preventing the spread of Covid-19, the best kind of double-masking is when you and the person you are interacting with are each correctly wearing a very snug-fitting mask."

Full study results have been published in JAMA Internal Medicine.