What Is the Best Material for a Reusable Face Mask? Here's What an Expert Says
After weeks of insisting that only health care workers or those who have COVID-19 need to wear face masks, the Centers for Disease Control and Prevention (CDC) has made a complete 360. During a press conference on April 3, President Donald Trump announced that the “CDC is advising the use of non-medical cloth faced covering as an additional voluntary public health measure.”
The new advice is based on recent studies, which show that a significant portion of individuals with the new coronavirus lack symptoms, and that even those who develop symptoms can transmit the virus to others before showing those symptoms.
“A mask can serve as a physical barrier to a person's coughs or sneezes, however, it’s still unclear how contagious someone without symptoms actually is or what the mechanism of spread is, for instance, breathing vs.singing vs. sharing utensils,” Amesh Adalja, MD, senior scholar at the Johns Hopkins University Center for Health Security, tells Health.
Despite the unknowns, it's better that the public use a cloth mask, says Dr. Adalja, rather than create supply issues for health care workers who need hospital grade masks, like the N95.
So what's the best material to use for a face mask, and where can you find it?
The CDC suggests using an old scarf, a hand towel, bandana, or even a coffee filter to make your own mask. It also provides instructions for a sewn cloth face covering using two rectangles of cotton fabric—preferably “tightly woven cotton, such as quilting fabric or cotton sheets,” although “T-shirt fabric will work in a pinch.” (Dr. Adams goes through the steps in a video posted to the CDC website, if you need a demo on how to do it.)
So there are a several options available in your closet or dresser drawer; you could also find these in any clothing retailer or crafts or fabric store. But which is best?
A recent study led by Scott Segal, MD, chair of anesthesiology at Wake Forest Baptist Health in Winston-Salem, North Carolina, in partnership with the Wake Forest Institute for Regenerative Medicine, tested a range of cloth materials to see how effective they would be as face masks.
The research, which hasn’t been submitted for publication or peer-reviewed, shows a wide variety of results. For instance, one piece of cloth filtered only 1% of particles, while another filtered 79%—more than the surgical masks, which were found to filter between 62-65% of particles.
Overall, thicker, higher-grade cotton fabrics performed better than those with lower thread counts and more open weave, Dr. Segal tells Health. And if you’re not sure if the fabric you have at home is thick enough, he suggests holding it up to a bright light or the sun.
“If light easily filters through, the filtration is likely not as good,” says Dr. Segal. “If it blocks more of the light, it likely performs better.”
The study found that so-called “quilting cotton” was generally much better than the sort of printed fabric available in discount fabric stores. “It tends to have the characteristics we found most effective: thicker, heavier yarn, higher thread count, tighter weave,” says Dr. Segal. So if you know any quilters, now’s the time to call in that favor.
If you do have to use lower-end cotton on the outside, Dr. Segal suggests using flannel as an inner layer. “Two-layer masks performed better than single layer masks,” he says. “This is probably because the small particles would have to find their way through both layers to pass through the mask. In our hands, cloth, single-layer masks did not perform well.”
Just as important as filtration is breathability. Remember, you need to wear this thing. “If you can’t comfortably breathe through the material for several minutes, it won’t make a good mask, no matter how effective it is in filtering,” adds Dr. Segal.
If you can get your hands on quilting cotton, great. If not, don’t panic. “The CDC recommendation is based on preventing the wearer from infecting others if they are infected and don’t know it, not so much on offering protection to the wearer,” says Dr. Segal. “Anything that prevents the spread of respiratory droplets is better than nothing—this is why we’re asked to cough or sneeze into our elbows.”
So if all you have is an old T-shirt or a bandana, you shouldn’t shy away from making a mask. And whatever material you use, make sure you wash it after each wear. “A homemade mask should be kept as clean as possible,” says Dr. Adalja. “Contaminating yourself with an infected mask is a real risk.”
Finally, never think a mask gives you immunity against the coronavirus. It’s crucial to continue to follow all other guidelines. “No mask is as good as social distancing and good hygiene,” advises Dr. Segal. “That’s still the number one way to protect yourself and others."
The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.
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