NEWS | February 10, 2021

Two masks can be better than one against COVID-19

CDC recommends either two masks or one tightly fitted mask with at least two layers

(SACRAMENTO)

If one mask is good for protecting you against COVID-19, then two masks are even better. That is the recommendation of the Centers for Disease Control and Prevention (CDC). 

If you double mask, wear a disposable or surgical mask underneath and a cloth mask on the outside for a tight fit. If you double mask, wear a disposable or surgical mask underneath and a cloth mask on the outside for a tight fit.

It issued new guidelines that say the best way to protect yourself from COVID-19 – along with social distancing – is to wear either two masks, with the cloth mask outside a surgical mask, or one tightly fitted mask with two or more layers. 

The CDC said lab tests showed people can reduce their exposure to the coronavirus by more than 95% if they wear two masks or adjust one surgical mask to fit more tightly by knotting the ear loops. The CDC report builds on a compilation of evidence by the Journal of the American Medical Association that demonstrates the effectiveness of masks against COVID-19. 

“It’s good to see the new guidelines and data because this is a subject that has drawn a lot of interest,” said Natascha Tuznik, UC Davis Health assistant clinical professor of infectious diseases

As with so much else involving COVID-19, experts are still refining the science of wearing a mask. Tuznik said the CDC guidelines make the concept of double masking clear after some speculation. 

Many health experts had suggested wearing two masks, but without data, they could only say the benefits seemed logical. Even Anthony Fauci, the nation’s top infectious disease expert and chief medical advisor to President Biden, reflected the previous lack of solid ground. He told the “Today” show recently that double masking “just makes common sense that it likely would be more effective.” 

“The way you’re likely to get COVID-19 is to be indoors with people you don’t live with. So, until we're all vaccinated, stay six feet apart and wear the best mask possible.”

— Mark Henderson

Mark Henderson, UC Davis Health professor of internal medicine and the department’s vice chair for education, said it’s important for people to know that new guidelines come from better, more complete information. 

“This is how scientific knowledge works,” he said. “It improves with studies, experience and analysis. Everything we know about COVID-19 we’ve essentially learned in the last year. Our knowledge is in its infancy and it will continue to evolve.” 

What to know about double masking

  • Two masks appear to work best with a surgical mask or similar disposable mask as the first layer. A tight-fitting cloth mask works best on the outside. 
  • A tight-fitting cloth mask also works well over a looser cloth mask, bandana or gaiter. They add another filter and make a more secure fit. 
  • Medical grade N95s don’t require a second mask in most cases, although in a high-risk situation, a cloth mask over it might be helpful – but be careful not to loosen the tight seal. However, experts continue to ask non-health care workers not to buy medical grade N95s. 

    “Please leave them for health care workers,” Tuznik said. “You can opt to double up with a good cloth mask or use one of the KN95s.” 

    KN95s are the pointed masks. In many cases, they are not approved for medical use but do provide substantial protection. The U.S. Food & Drug Administration (FDA) gave Emergency Use Authorization to some KN95s and lists them here.

What to know about a tighter fit or a single mask

  • The study showed that surgical masks on their own can be just as effective against COVID-19 as double masks. Here’s how: First, knot the ear loops to pull the mask tighter. Then, tuck in any extra fabric at the edges or around your chin to close any gaps. 
  • For non-surgical masks, the CDC recommends masks with two or more layers of thick but breathable fabric worn tightly. 

    “If you have a cloth mask, ideally it should be double or triple layered and cotton, the higher the thread count the better,” Tuznik said. “It should look heavy duty and be sure it fits snugly.” 
  • There are a handful of mask tighteners hitting the market and others are being studied. In fact, one recent report even suggests wrapping a nylon stocking around your head and mask to get a tighter fit. For the moment, Tuznik is a bit skeptical of some of those ideas. 

    “I think it’s asking an awful lot from people,” she said. “We’ll see what the future brings with more data and whether people will actually do that.”
“If you give a big inhale and exhale, you want to see your mask moving in and out. That means you’re breathing through your filters. If nothing moves, that’s bad. That means the air is moving through gaps in the sides and you’re not protected.”

— Natascha Tuznik

When to double mask

Whenever you’re in a higher risk situation, especially around people not in your household, consider wearing two masks if you can. 

“The way you’re likely to get COVID-19 is to be indoors with people you don’t live with,” Henderson said. “So, until we’re all vaccinated, stay six feet apart and wear the best mask possible.” 

Thin masks, bandanas, gaiters and many fashion masks fall short. They may be fine for a walk or sitting socially distanced outdoors, but they call for a second mask if you wear them indoors around others. 

“A lot of the fashion masks aren’t that great, despite the price,” Tuznik said. “I have one that I love. I got it a long time ago – back when it was just, ‘put a mask on’ – but it’s pretty flimsy. Sadly, I won’t be using that one anymore.” 

How do I know my mask or masks fit correctly?

“If you give a big inhale and exhale, you want to see your mask moving in and out,” Tuznik said. “That means you’re breathing through your filters. If nothing moves, that’s bad. That means the air is moving through gaps in the sides and you’re not protected.” 

This is one concern about double masking: You can defeat the masks by making them too thick. 

“If it’s hard for you to breathe through your mask, the air will find the openings where there is no filter,” Tuznik said. “That’s where the virus can get in.” 

The bottom line: Wear a mask.

The new guidelines emphasize another clear point: Wearing any kind of mask helps prevent COVID-19 and could save your life or the life of someone you love. 

 “If everyone would just wear any kind of mask, we wouldn’t have to worry about these nuances,” Henderson said. “Multiple studies have shown that universal masking prevents disease, lowers mortality and eases the economic burden from COVID-19 on the community.” 

 “It comes down to this,” Tuznik said. “Any mask is so much better for everyone than nothing.”