TUESDAY, April 20, 2021 (HealthDay News) -- Wearing two snug, well-fitted face masks can significantly reduce your risk of coronavirus infection, researchers say.
But a good fit is key: The new study found that two ill-fitting cloth masks don't provide as much protection as one snug-fitting surgical mask.
"We've found that wearing two loosely fitted masks will not give you the filtration benefit that one, snug-fitting procedure mask will," said lead author Emily Sickbert-Bennett. She's an associate professor of infectious diseases at the University of North Carolina at Chapel Hill.
The new findings follow a recent update from the U.S. Centers for Disease Control and Prevention, which recommends double-masking.
In a series of lab tests, the UNC team assessed the fitted filtration efficiency (FFE) of a range of masks.
They found that the filtration efficiency differs from person to person, due to each individual's face shape and mask fit.
Without altering the fit, a surgical mask (also known as a procedure mask) is between 40% and 60% effective at keeping COVID19-sized particles out, while a cloth mask is about 40% effective, the study found.
A cloth mask placed over a surgical mask improved the effectiveness by about 20%. Protection was even better when the layering was done with a snug-fitting, sleeve-type mask, such as a gaiter.
Layering cloth masks over surgical masks eliminates gaps and holds the surgical mask closer to the face, consistently covering the nose and mouth, researchers found.
When a surgical mask is worn over a cloth mask, FFE improved by 16%. The findings were published April 16 in the journal JAMA Internal Medicine.
"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," Sickbert-Bennett said in a university news release.
The U.S. Centers for Disease Control and Prevention has more on wearing masks.
SOURCE: University of North Carolina at Chapel Hill, news release, April 16, 2021