Should you wear two masks to ward off COVID? Here’s something that matters more
People have begun wearing two masks to protect themselves and others from the spread of the coronavirus, after the Centers for Disease Control and Prevention suggested recently that it might be a good idea.
But researchers at the University of North Carolina at Chapel Hill have found that how a mask fits is more important than whether you’re wearing one or two of them.
Experiments conducted at an Environmental Protection Agency lab on the UNC campus found that a poorly fitted surgical mask allows small particles in through gaps around the edges, particularly as people move their head. Adding a second surgical mask on top improves the filtration efficiency by about 15%, said Phillip Clapp, an aerosol toxicology expert the UNC School of Medicine.
“If you have someone who can check to see the gaps around your face, that’s the way you can get the most immediate benefit from even a single mask,” Clapp said at a Zoom press conference on Friday. “Beyond that, if you’ve already done that step, you can expect to get a slight bump in the filtration efficiency by adding a second mask on top of it.”
The best double-masking scenario, Clapp said, involves putting a tighter-fitting cloth mask over a surgical mask, to eliminate those gaps. That combination was 40% more effective than a single mask, he said.
The research included good news for those fond of neck gaiters, those tubes of fabric worn around the neck for warmth or fashion. Last summer, researchers at Duke University published a study that suggested some gaiters are too thin to be effective at blocking airborne particles, news that traveled around the world.
But combining a gaiter with a surgical or procedure mask makes sense, Clapp said, and worked better than simply doubling up on surgical masks.
“The gaiter actually performed quite well in these studies because it’s tight to the face,” he said. “If you put a procedure mask under that and you use that to pull the procedure mask very tight, the gaiter went up by 40% effectiveness as well.”
The understanding of the effectiveness of masks has evolved during the COVID-19 pandemic, said Dr. Emily Sickbert-Bennett, director of infection prevention at UNC Medical Center. Early on, Sickbert-Bennett said, many people thought the main benefit of wearing a mask was to protect others rather than to protect yourself.
Since then, scientists have tested the flow of particles through and around various types of masks and mask materials, showing that wearing a mask is one of the best ways to contain the spread of the coronavirus for everyone.
“First and foremost, double-masking in the form of you and the person you’re interacting with both having a mask on is the most important double-masking there is,” Sickbert-Bennett said at the UNC press conference.
She added that making sure a single mask fits snugly over the mouth and nose, without sags or gaps, can improve its efficiency by 20%.
“Fit really matters,” she said.
Clapp said the researchers were unable to find a double-masking combination that was as effective as an N95 respirator, a type of mask that prevents at least 95% of airborne particles from entering the wearer’s mouth and nose, if worn properly.
Clapp said wearing a second mask with an N95 respirator is not only unnecessary but could be harmful. That’s because an N95 alone is difficult to breath through for long periods of time.
“So if you start layering things over a mask that’s already hard to breathe through, you’re really going to strain your breathing, and it’s not going to be something that’s really sustainable. It’s going to likely result in people wanting to remove their mask more often,” he said. “The best mask is one that you’ll continue to wear.”
