Masks and Covid

The US Centers for Disease Control and Prevention has changed its mask guidelines to recommend that people "wear the most protective mask you can that fits well and that you will wear consistently." The agency describes well-fitting respirators approved by the National Institute of Occupational Safety & Health (NIOSH) – such as N95 masks – as offering "the highest level of protection."

The updated guidelines come after many public health experts have been recommending for months that people wear more effective masks – particularly N95s – and that the CDC change its guidelines on mask-wearing.

"Cloth masks are little more than facial decorations. There's no place for them in light of Omicron," CNN medical analyst Dr. Leana Wen, an emergency physician and visiting professor of health policy and management at the George Washington University Milken Institute School of Public Health, recently said on "CNN Newsroom."

In crowded places, "you should be wearing a KN95 or N95 mask," which can cost a few dollars each, Wen added. Due to certain materials – such as polypropylene fibers – acting as both mechanical and electrostatic barriers, these masks better prevent tiny particles from getting into your nose or mouth and must be fitted to your face to function properly.

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N95s are more widely available now than they were earlier in the pandemic, and public health experts in the US also have a better understanding that the primary driver of coronavirus infection is shared air, Erin Bromage, an associate professor of biology at the University of Massachusetts Dartmouth, told CNN last month.

Cloth masks – encouraged earlier in the pandemic – can filter large droplets, while more effective masks, such as N95s, can filter both large droplets and the smaller aerosols or particles potentially laden with airborne virus if infected people are present, Bromage said.

A cloth face covering has 75% inward and outward leakage, which the American Conference of Governmental Industrial Hygienists defines as the "percentage of particles entering the facepiece" and the "percentage of particles exhaled by a source exiting the facepiece," respectively.

Properly fitted N95 respirators approved by NIOSH can filter up to 95% of particles in the air.

Why the Omicron variant of coronavirus has been infecting many people so quickly is currently unknown, but it emphasizes the importance of wearing high-quality masks, Bromage said.

"If it is less virus needed, or if it is a person who's infected is putting more virus out, then the role of a mask in this is, if we can cut down the amount that you’re actually breathing in, you get more time" before potentially getting infected, he added.

The difference between N95 and KN95 masks is where each is certified, according to Oklahoma's state health department. The US tests, certifies and regulates the N95s public health experts have been recommending; in contrast, manufacturers in China test KN95s, but the country's government doesn't have a regulatory body that's validating them, said Aaron Collins, a professor emeritus at Mercer University's School of Engineering and a mechanical engineer with a background in aerosol science.

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Roughly 60% of KN95 respirators NIOSH evaluated during the pandemic in 2020 and 2021 didn't meet the requirements they were intended to meet, according to the CDC.

"If they’re made to the standard and certified by the appropriate boards in their country like NIOSH here, they all do basically the same thing," Bromage said. They "may meet the standards, but they’re not certified to meet it. And there's others that clearly don't."

KF94 masks are Korean-standard masks tested and regulated by the Korean Ministry of Food and Drug Safety, said Kelly Carothers, the director of government affairs and sustainability at Project N95, the national clearinghouse working to provide equitable access to personal protective equipment and coronavirus tests.

The CDC has advised people to not wear international respirators with exhalation valves, vents or other openings, as such openings can emit unfiltered exhaled air into surrounding areas – which would be problematic if you’re infected and breathing out virus particles that could infect others, Wen told CNN this month.

The level of potential virus escape is low, though, she added. N95s with exhalation valves work as well as cloth or surgical masks do in protecting others. An N95 with a valve isn't recommended above N95s without valves, but if the former is the only mask you can wear, do that, Wen suggested.

NIOSH has a list of approved N95 respirators. These masks should have a cup, flat fold or duck bill shape; two straps that go around your head; an adjustable wire nose bridge; and appropriate markings indicating NIOSH approval, the CDC says.

The agency also has resources for identifying counterfeit N95 masks, the signs of which include a total absence of markings on the mask or NIOSH spelled incorrectly. The resources also cover properly putting the N95 on, taking it off and performing a respirator seal check.

The CDC has a list of signs a KN95 respirator might be counterfeit, which include manufacturer claims that the KN95 mask has been approved or certified by the CDC or NIOSH.

"If you’re going to look for a KN95 mask, what we would recommend is to make sure that it has the (Chinese government) standard written on the side of the mask, similar to NIOSH" standards for US N95s, Carothers said.

Those Chinese government standards on KN95s should say GB 2626-2019 or GB 2626-2006, which was the standard before GB 2626-2019, Carothers advised.

The Korean ministry has an online database of approved KF94 manufacturers, but the webpage is in Korean and might not be totally and accurately translated by your internet browser's translation plugin. There are, however, some tips in English on these graphics for checking marks when buying KF94 masks, including packaging that features the words "Quasi-Drug Product" and "KF94."

The N95s are medical masks made for health care workers, so, naturally, there aren't N95 masks designed or made for children, since only adults would be working in health care settings.

Larger children within the elementary to middle school age range and older could, however, potentially wear N95s that come in small sizes intended for adults, Linsey Marr, a professor of civil and environmental engineering at Virginia Tech, told CNN this month.

"If you see an N95 as marketed for children, that should raise a red flag," Marr said. "There will be KN95 and KF94s that are designed for and marketed for children. With those, it's the same issue as we discussed for adults, which is to make sure you’re getting them from a trusted, reputable source.

"… Certainly, for children, a KN95 or KF94 will provide better protection on average than a surgical mask or cloth mask," Marr added.

If you have trouble fitting a KN95, KF94 or N95 to your child's face regardless of how many brands you have tried, you can tie the ear loops or use toggles or cord lock adjusters to ensure the mask fits tightly enough, Marr suggested. The CDC's knot and tuck method could also work.

Specially labeled "surgical" N95s "should be reserved for use by healthcare personnel," the CDC says, but other N95s can be found at some home improvement stores, retailers and drugstores.

N95 masks made by 3M – a leading global manufacturer of N95 masks and the largest producer of the masks in the US – are available at all major retailers, including Home Depot, Target, Lowes, Menards and Amazon's 3M store, 3M spokeswoman Jennifer Ehrlich told CNN this month.

Amazon has said it prohibits sellers from claiming their KN95 masks are "FDA-approved," since the US Food and Drug Administration doesn't approve KN95 masks.

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"If you’re going to go to Amazon, just make sure you’re buying from the (N95) manufacturer's direct store, like their official store" on Amazon, Collins said.

For both children and adults, Project N95 is a reputable source from which you can get N95s, KN95s and KF94s, Marr said.

As consumer demand for these masks have increased, there have been reports of price gouging online. Some public health departments, such as those for Maryland and Milwaukee, are offering free N95 masks.

In medical settings, health care staff frequently change masks to avoid cross-contaminating a patient's room with equipment that was worn in a different space with an infectious person, Bromage explained. "When you take a medical-grade thing that's single use and then put it in the general public, we’re not worried about you cross-contaminating different environments. … It's really about providing protection to you."

So, yes, you can reuse your N95 mask.

Even after wearing an N95 in a crowded indoor setting – such as a subway or grocery store – an N95's material and filtration ability aren't "going to degrade unless you physically rub it or poke holes in it," said Marr, adding that she wears her N95 masks for a week. "You’d have to be in really polluted air … for several days before it lost its ability to filter out particles."

However, there are things to keep in mind to reuse an N95 safely: When putting it on, avoid touching the front outer part of the mask; instead handle it by its edges or straps.

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Also, if you learn you were near someone infected with coronavirus while you were wearing an N95, you should throw out that mask so you don't risk contact with the virus, Bromage advised. Unknowingly being exposed to infected people while wearing an N95 is possible, so distancing as much as possible can help reduce risk.

If the mask becomes damp, visibly dirty, bent, creased, difficult to breathe through or otherwise damaged – including from makeup – you should replace it to avoid wearing a less effective mask, Marr and Bromage said.

You shouldn't wash an N95, since water would dissipate the mask's special static charge that helps it filter out viruses so well, Marr said.

What you can do is set the mask aside, because particles will die off within several hours, she added, and that will occur even faster when you place it in sunlight.

But the fact that warmer temperatures can have a "sanitizing" effect on N95s doesn't mean you should throw the masks in an oven or microwave, Bromage said. That could ruin the mask. "I used to stick mine on the dashboard of my car in summer, and that would do more than enough."

This story has been updated with additional information about N95s with exhalation valves.

CNN's Katherine Dillinger and John Bonifield contributed to this story.