Find out the updated guidelines about wearing two masks, how to make a mask fit better, which mask protects you best, and more.

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As more contagious variants of COVID-19 continue to spread across the United States, the Centers for Disease Control (CDC) has officially updated its guidance to recommend double-masking and the use of a surgical mask with a tight fit to maximize protection against the virus.

With vaccines from Pfizer and Moderna already out and others on the way, it might seem like masking isn't as essential as it once was to getting the pandemic under control. But the new CDC guidance, which echoes the recommendation made by White House chief medical advisor Anthony Fauci in January, serve as a reminder that vaccines alone won't cut it.

For starters, the vaccine rollout is slow-going (if improving) and only a small portion of the population is currently vaccinated. Plus, while the vaccine helps protect against contracting the virus, we still don't know whether it helps prevent the spread of it. So your 70-year-old mom who got vaccinated last month? She could be an unwitting host.

The reality is that the virus still has millions of people through which it can pass, and without the widespread use of masks for the foreseeable future, including among people who have been vaccinated, it will continue to do just that. Scary? Yes. But the good news is that mask-wearing is, without question, effective—especially if you do it with best practices in mind. 

The new CDC double-masking guidance

The point of wearing a mask is to create a barrier that makes it harder for your respiratory droplets and aerosols to spread to other people and for theirs to spread to you. So it stands to reason that adding more layers to your face might achieve better results. 

But "double-masking" can be a somewhat misleading term. "It doesn't mean that layering two of any random type of mask on top of each other is always better," Linsey Marr, PhD, the Charles P. Lunsford professor of civil and environmental engineering at Virginia Tech and an expert in airborne disease transmission, tells Health. "It's kind of a shorthand for 'improving the fit and filtration of your mask.'"

With that more specific goal in mind, Marr—and now the CDC—recommends layering a well-fitted cloth mask over a proper surgical mask. (Look for surgical masks that are made of polypropylene and, ideally, ASTM-certified.)  

"Surgical masks made of the right type of material—not the paper ones—are really good filter material," says Marr. "But you're taking this blue rectangle and you're trying to fit it to your face, and it doesn't fit very well—and we know that even a small area of leakage, just 1-2%, means you've degraded the performance of your mask by 50%. So if you take a good, tight-fitting cloth mask and put it over that, then you can greatly improve the fit and you're adding another layer of filtration." 

Another way to double-mask is to not really double-mask at all, but to think in terms of layers. Marr recommends wearing a well-fitted cloth mask with a pocket on the inside and adding a high-quality filter material such as a vacuum bag or HEPA filter. That way, you get three layers of protection in just one face-hugging mask. 

Alternatively, the CDC recommends improving the fit of a single surgical mask, which has two layers, by knotting the ear loops and tucking in the sides close to the face. According to a new report, doing so can reduce exposure to potentially infected aerosols by 95%. (Same goes for wearing a cloth mask over a surgical mask.)

"If you already have a three-layer fabric mask that fits you really well, you don't need to go out and buy more masks just to wear two," Janet Baseman, PhD, professor of epidemiology and associate dean at the University of Washington School of Public Health, tells Health.

What about triple-masking? 

"[People think], 'Oh, if double-masking is good then triple-masking must be even better,' and they just add umpteen layers," says Marr. "But you get diminishing returns beyond a certain point."

And that's not just because the more masks you wear, the harder it is for you to breathe (although that's certainly true)—but also because the more masks you wear, the greater the odds are that air will leak out around the sides. 

"Air is going to want to take the path of least resistance," Marr explains. "So if there's so many layers [to your face-covering] that they block airflow through the front of the mask, then if there's just even a small leak on the side, more air is going to be passing through that."

N95s v. KN95s v. KF94s

The gold standard among masks is still the N95, a medical-grade mask that when worn correctly filters out 95% of aerosol particles as tiny as 0.3 microns. But because N95s are in short supply and have been since last year, the CDC is still recommending they be reserved for health care workers. 

Two alternatives have gained popularity in their place: The KN95, or the Chinese equivalent of the N95, which filters out 95% of aerosol particles; and the KF94, or the Korean equivalent of the N95, which filters out 94% of aerosol particles. The difference between those options and the N95 is that, unlike the latter, they aren't tested and certified by the National Institute for Occupational Safety and Health (NIOSH), which means there's less certainty around their efficacy. (Still, the US Food and Drug Association has in the past year approved KN95s for emergency medical use.) 

Unfortunately, just as counterfeit N95s have cropped up on the market, so too have counterfeit KN95s and KF94s. "I've seen test results for some of the KN95s where some are great, they perform as well as an N95, but others are like 15% efficient,"  says Marr. "I'm not sure I'd be able to tell [which is which] without testing them." 

To avoid being duped—and risking your safety—check out these tips from the CDC on spotting counterfeits, and review the FDA's approved list of emergency PPE. Depending on your circumstances, if you're still not sure whether a KN95 you're considering is legit, you may be better off going with the other options listed above. 

Guidelines for cloth masks

According to CDC guidelines, the bare minimum is a washable, breathable-fabric mask that has two layers or more. What kind of fabric, exactly? Experts agree that 100% cotton works better than a synthetic material like acrylic or polyester. 

"My guess is that, because cotton is a natural material, the threads are a little more frayed," says Marr. "That adds more of an obstacle course for the airflow to go around, and then more places for particles to crash into. And that's going to work better compared to a synthetic fiber, which is very uniform and not rough."

Remember to wash it regularly as well. A good rule of thumb is to toss a cloth mask in the washing machine at the end of the day. (A surgical mask is disposable, so toss that out at the end of the day.) Use a warm water setting for your cloth mask; you can also wash it by scrubbing it in soapy water for 20 seconds, according to the Mayo Clinic.

The best type of mask depends on your environment 

Not all masks are created equal, but neither are all environments—some are riskier than others. With that in mind, it's okay to tailor the mask you're wearing to the setting you're wearing it in. 

Walking your dog alone? A cloth mask is probably fine. Going to the doctor's office? A surgical-mask-cloth-mask combo would be better. "I have a lot of different material masks," says Baseman. "When I am outside, where the rate of transmission is really low, I wear a cloth mask. When I go to the grocery store, I wear a KN95 mask." 

If you similarly decide to match your mask to your surroundings, keep in mind that you still need to practice other safety measures to minimize your risk: Stay at least six-feet away from other people and keep your time spent indoors to a minimum. 

"I go into the grocery store with a list, and I get out of there," says Baseman. "The duration of the exposure is still of interest and of importance."

Other guidelines for wearing a mask

The CDC advises that everyone over the age of two wear a mask "in public settings, at events and gatherings, and anywhere they'll be around other people." Earlier this month, the CDC also mandated the use of face masks on public transportation. So, basically, you should wear a mask any time you leave your house, just as you would a coat or a hat.

Despite these guidelines and the effectiveness of masks, many people still refuse to wear them, and that puts a major ding in our collective safety.

"Here in Tennessee we still hear this a lot: 'It'll be my decision whether I [wear a mask]. If I'm feeling well I don't see why I have to,'" William Schaffner, MD, a professor of preventive medicine in the department of health policy as well as a professor of medicine in the division of infectious diseases at the Vanderbilt University School of Medicine, tells Health

"Well, it's really not so much a matter of individual decision-making," he says. "This is a communicable disease. When we live close to each other, we sometimes do things that may not be our own individual inclination right at that moment, but we do them in order for the entire society to function coherently. Like stopping at a red light." 

Given how much resistance to mask-wearing is still out there, he's less concerned about getting people to wear a certain kind of mask and more focused on getting them to wear a mask, period. "If I had one wish, it wouldn't be about two masks or N95s," he says. "It would be just that everyone would wear a regular fabric or surgical mask, and wear them over the nose, every time they leave their front door."

And, yes, he means every time. "People ask me, 'Well, if I go walking down the sidewalk and I'm by myself or with my life partner who I live with, and we're not around anybody else, why should I wear a mask?'" he says. "The answer is: 'So that everybody sees you wearing the mask, and you have helped make it the social norm.' If there are people who are not wearing the mask doing this or that, that creates confusion."

The other benefit to wearing your mask whenever you're out: It becomes second-nature. "Just wear the mask," Dr. Schaffner says. "It's not that big a deal." 

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 EatingWell 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 CDCWHO, and their local public health department as resources.

This story originally appeared on health.com