Two methods substantially boost fit and protection, according to a CDC report and guidance released Wednesday. One is wearing a cloth mask over a surgical mask. The second is improving the fit of a single surgical mask by knotting the ear loops and tucking in the sides close to the face to prevent air from leaking out around the edges and to form a closer fit.
Both of those methods reduced exposure to potentially infectious aerosols by more than 95 percent in a laboratory experiment using dummies, the report said.
A year after the coronavirus’ arrival in the United States, — with the death toll approaching 500,000 — the updated guidance stresses the importance of mask-wearing as one of the best defenses against more transmissible variants, along with social distancing, avoiding crowds and poorly ventilated indoor spaces, and practicing frequent hand washing.
It represents a new administration’s effort to present clear instructions to Americans after the mixed messaging of the prior one in which health officials urged mask-wearing, but President Trump refused to do so and ridiculed those who did. In part as a result, many Americans refuse to wear them.
The instructions also come at a potentially perilous moment as health officials race to vaccinate tens of millions of peoples to protect them from more transmissible and possibly more lethal variants, but remain hampered by a limited vaccine supply.
Until now, CDC’s recommendation has focused on cloth masks because of worries about a shortage of medical procedure masks and N95 respirators masks for health-care personnel. But as supply has improved, the agency is providing information about the pros and cons of different masks “so consumers can make an informed choice about what they want to use,” Brooks said.
President Biden has urged all Americans to wear masks and signed executive orders requiring their use on federal property and on planes, trains and buses. Thirty-six state governments currently require people to wear face coverings in public to curb the spread of the coronavirus, according to a tally by AARP. The District of Columbia and Puerto Rico also have mask orders. Meanwhile, three states — Iowa, North Dakota and Mississippi — have lifted such mandates.
Brooks and other public health experts say the key takeaway of the new guidelines is mask fit, which improves filtration, or the ability of material to block tiny particles.
“Double masking is one way you can do it,” he said, noting that double masking does not mean double protection. “It may not be the right solution for everybody,” he added. For some people, wearing two masks can impede breathing or obstruct peripheral vision that could lead to a fall and result in injury.
Surgical masks can also be adjusted to make them better fit the contours of the face, Brooks said. The three-ply masks, which may be flat pleated or cone shaped, are not designed to protect against infections from viruses and bacteria, but rather to prevent contamination of sterile surgical sites and to prevent blood and other fluids from splashing onto the wearer’s mouth and nose.
Knotting the medical procedure mask where the loops attach to the face helps the mask fit closer to your face, but it also slightly reduces mask size, he said.
“People with big faces may have difficulty getting the mask to cover their nose and mouth completely when they do the knot, so you really have to look around and find a technique that works well for you,” Brooks said.
Studies have shown that fit also can be improved using simple materials, including nylon hosiery around the neck and over either a cloth or surgical mask, and the use of mask fitters — adjustable frames or braces worn either as ear loops or behind the head to secure face-coverings tightly on noses.
CDC conducted experiments last month to test the effectiveness of mask combinations at reducing the amount of particles released during a cough. A three-ply surgical mask blocked 42 percent of particles from a simulated cough, and a three-ply cloth mask blocked 44 percent. But a cloth mask covering a medical mask blocked 92 percent of the particles, the report said.
In a second experiment, a dummy wearing double masks and one wearing a knotted/tucked medical reduced exposure for an unmasked dummy by 82 percent and 62 percent respectively. When one dummy was not wearing any masks and the one acting as the bystander wore a double mask or a knotted/tucked medical mask, the bystander’s exposure was reduced by 83 and 64.5 percent respectively.
But when both dummies wore double masks or knotted/tucked medical masks, the bystander’s exposure was reduced by more than 95 percent in both situations.
Brooks cautioned against generalizing the numeric findings of the studies, however. The experiments used one type of cotton mask and one type of medical mask in a laboratory, “not with human beings,” he said.
Other experts expressed concern that double masking could discourage mask-wearing.
“I would rather people focus on finding one quality mask that meets the mark, versus trying to layer masks and create discomfort, difficulty breathing … or frustration that might lead to no mask at all,” said Saskia Popescu, an infectious-disease epidemiologist and assistant professor at George Mason University.
David Rothamer, an engineering professor at the University of Wisconsin Madison, has experimented with masks on mannequins in classrooms while studying the best ways to prevent the spread of the virus in college classes. He said he is not a proponent of double masking because it consumes more masks, and can also lead to more air leakage.
“The only reason to [wear two masks] is if you can get better fit,” he said.
Linsey Marr, an engineering professor at Virginia Tech who has studied how to maximize mask efficiency, offered these tips for ensuring the best mask fit:
“You should not be able to see or feel any kind of open spots around the edges of your mask, especially around your nose, which is why a metal bridge is so important for fitting tightly around the nose.
“You don’t want gaps around the cheek or chin, really anywhere,” she said. “One way you can check for that is when you are breathing through it, does it feel like air is leaking out of the side? Put your hand on the edge to see if you feel anything. When you breathe in, you should feel suction up against your face.”
Other signs of leakage include eyeglasses fogging up or cold breath coming from the sides of masks while outside, she said.
Another test involves breathing hard in front of a mirror to see if you blink while wearing a mask, which would indicate leakage from the top of the mask.
If masks fail these tests, Marr said, you should try a different kind of mask. “Peoples’ faces have such different shapes that you can try to find something that can work better for your face,” she advised.
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