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Doctors & Advice, Family Health

Should You Double-Mask? It Depends


Advice on face coverings amid the COVID-19 pandemic is changing—here’s some help.

Information in this article was accurate at the time of original publication. Because information about COVID-19 changes rapidly, we encourage you to visit the websites of the Centers for Disease Control & Prevention (CDC), World Health Organization (WHO), and your state and local government for the latest information.

A key recommendation throughout the pandemic has been to wear a face mask to protect others (and yourself) from COVID-19. Experts say that strategy is even more important as new variants of the SARS CoV-2 virus circulate. But the problem is, there are tons of masks on the market now and many variations on how they are made. And many are counterfeit. So, which one should you wear? How should it fit? Should you double your masks?   

The answer, according to Heidi Zapata, MD, PhD, a Yale Medicine immunologist and infectious diseases specialist, is to keep it simple. “Basically, people need to wear a good mask and wear it correctly, over both their mouth and nose,” says Dr. Zapata. If a mask is uncomfortable, you’ll be less likely to wear it or keep it on if you do, she adds.

We talked to Dr. Zapata and other Yale Medicine infectious diseases experts to help answer the new questions that are coming up about masks.

So, what is a ‘good’ mask?

The Centers for Disease Control and Prevention (CDC) updated its advice on masks in early February after releasing new research that suggested virus transmission could be reduced by 96.5% when an infected person or an uninfected person wears a mask—but it must be a well-fitting one, worn properly. The CDC reached its conclusion after conducting experiments in which it simulated aerosol production from a cough and studied how those aerosols penetrated different types of masks.

New CDC guidance for improving mask use recommends a high-quality mask that fits well and has multiple layers of fabric. “This can be achieved by doubling up on masks, but that’s not necessary if you have one well-fitted quality mask,” says Yale Medicine infectious diseases specialist Richard Martinello, MD. (If you do double up, the CDC recommends wearing one disposable mask underneath a cloth mask, but wearing two disposable masks is not advised. The second mask should push the edges of the inner mask against the face, and the mask should fit snugly.) 

How should you choose a mask?

Material makes a difference in a mask—both the type and the amount, says Dr. Martinello. “Generally, cloth masks, especially cotton ones, are more effective than some of the synthetic materials such as acrylics,” he says. “At minimum, you want two layers, but three is generally superior to two.”

Richard Martinello, MD, believes a single high-quality mask with a filter is preferable to combining multiple masks. “Two masks may provide some more protection, but we don’t want to negatively impact how well it fits," he says.

A tightly woven cotton mask with two layers of fabric and a pocket in between where you can insert a filter is another option, Dr. Martinello says. “Coffee filters have been tested and they work surprisingly well,” he says.

If your budget is tight or if you prefer to avoid vetting masks online, the CDC provides both “sew” and “no-sew” instructions for making a cloth face mask. 

What about respirators such as N95s, KN95s, and KF94s?

The CDC has recommended against the use of N95 masks for nonmedical workers, saying they are still considered critical supplies that need to be reserved for health care workers and medical first responders.

But there may be other reasons not to use them. “People ask all the time if they should wear N95 respirators,” says Dr. Martinello. “While it’s very clear that they are superior in their ability to filter, we also know that they can be uncomfortable to wear and difficult to do so for prolonged periods of time. If someone is at work and they need to take their mask off because they are not comfortable, then there can be unintended consequences from that.”

Basically, people need to wear a good mask and wear it correctly, over both their mouth and nose.

Heidi Zapata, MD, PhD, a Yale Medicine infectious diseases expert

There is also recent talk of KN95 and KF94 masks—disposable respirators—which can be purchased online. N95s meet U.S. safety standards, whereas KN95 and KF94 masks meet Chinese and South Korean standards, respectively. The Food & Drug Administration (FDA) has issued an emergency use authorization for KN95s. If you do wear a KN95 mask, the CDC advises wearing only one mask at a time, and not combining it with another mask.

Dr. Martinello cautions that it is important to be aware that there are counterfeit masks in the marketplace. “It is the Wild West out there,” he says, noting that even supply chain professionals have been fooled by counterfeit products of questionable quality.

Some people have also used face coverings that aren’t effective for preventing infection. The CDC does not recommend face shields alone for prevention of COVID-19, since their efficacy is still being evaluated. Scarves, ski masks, and balaclavas are not suitable substitutions for masks either (in cold weather, you should wear your mask underneath these items), according to the CDC.

Should you double up on masks?

While the CDC recommends either single or double masks—as long as they are worn properly—Dr. Martinello believes a single high-quality mask with a filter is preferable to combining multiple masks.

“Two masks may provide some more protection, but we don’t want to negatively impact how well it fits,” he explains, noting that research by engineers (not yet published) raises concern that double-masking may create a higher level of resistance to air flow. “More of the air may be forced around the perimeter of the mask rather than going through the filter—if you have one,” explains Dr. Martinello. “If the masks are loose-fitting and you are layering up a bunch of additional materials, the air you are breathing is going through the sides, which can be counterproductive to the filter.”

The CDC says you can improve single mask use by wearing one that has a nose wire (a metal strip along the top of the mask that can be bent to fit your face that can also prevent fogging if you wear glasses), and using a mask fitter or brace over a disposable or cloth mask to prevent air from leaking around the edges. You should feel warm air come through the front of the mask, and may be able to see the mask move in and out with each breath.

How should you wear a mask and how should you wash it when you’re done?

The CDC has specific recommendations for the best ways to handle (and clean) masks.

  • Before you put on your mask, clean your hands with soap and water or hand sanitizer.
  • Put on your mask so it covers your nose and mouth, and secure it under your chin.
  • Do NOT touch your mask when wearing it. If you find you are touching or adjusting your mask, you may be wearing a mask that doesn’t fit you properly.
  • You should be able to breathe easily.
  • When you take off your mask, handle it by the ear loops or ties only, fold the outside corners together and put it in the laundry. Wash your hands immediately after handling or touching a used mask.
  • If you used a mask and it is wet, store it in a plastic bag until you can wash it.
  • Wash reusable masks regularly with your regular laundry. Use regular laundry detergent and the warmest appropriate water setting for the cloth. In the dryer, use the highest heat setting and don’t take masks out of the dryer until they are completely dry.

When should you wear a mask?

The CDC recommends wearing a mask around people who don’t live in your household, especially when you’re indoors, as well as in public settings—that includes events and gatherings, and anywhere else where you’re around other people. Masks are now required in the U.S. on planes, buses, trains, and other forms of public transportation traveling into, within, or out of the country, and in U.S. transportation hubs such as airports and stations.

It is the Wild West out there.

Richard Martinello, MD, a Yale Medicine infectious diseases expert, on how even supply chain professionals have been fooled by counterfeit products

Some situations are difficult. If you are eating in a restaurant, the CDC says you can take your mask off when you are actively eating or drinking, but otherwise recommends wearing it to reduce risk, particularly indoors, and when speaking with restaurant workers and servers.  

There are certain groups of people who should not wear masks. They include children younger than 2, people who have trouble breathing, or anyone who is unconscious, incapacitated, or otherwise unable to remove the mask without assistance. Some people with sensory, cognitive, or behavioral issues may have difficulties wearing or tolerating a mask and should not wear one. 

Wearing a mask is only one of several prevention strategies

Joseph Vinetz, MD, a Yale Medicine infectious diseases specialist, says people should understand that a mask is just one tool in the toolbox for preventing COVID-19. “We should do everything we can to slow the spread of the virus,” he says. But, “a mask should not give anyone a false sense of security. It doesn’t give you a license to have social gatherings.”

That means that even if you are wearing a mask, you still need to avoid crowds and poorly ventilated spaces, maintain a six-foot distance (about 2 arm lengths) from other people, wash your hands frequently, and avoid touching your face [which a mask can help with, since people are thought to put themselves at greater risk for infection when they transmit pathogens from their hands to their eyes, nose, and mouth], he says.

You need to wear a mask even after you get the vaccine.

Don’t throw away your mask once you are vaccinated against COVID-19. The Pfizer-BioNTech and Moderna vaccines—the two that are available so far—are deemed 95% effective, and while that provides strong protection, anyone who falls into the remaining 5% could still potentially become infected with the virus and spread it to others. So too could people who have been vaccinated, but are waiting for their immunity to build up, as well as those who are not getting the vaccine (whether by choice or because of a contraindication). Since many people with COVID-19 have no symptoms at all, it can be impossible to know who might be contagious.

So, for now the advice, whether you have gotten the vaccine or not, is to wear a mask—and keep wearing it—knowing that recommendations could change as experts learn more. “The science is evolving, and the CDC is reflecting that,” says Dr. Vinetz. “We should be doing what the CDC recommends. Masks won’t eliminate the virus, but they will perhaps reduce the rate of transmission.”