NIOSH-approved N95 masks are recommended to prevent the transmission of the COVID-19 omicron variant.

NIOSH-approved N95 masks are recommended to prevent the transmission of the COVID-19 omicron variant. / Jennifer Swanson/NPR

After months of public health experts urging Americans to start wearing higher quality masks, the Centers for Disease Control and Prevention on Friday updated its mask guidance for consumers. While the agency didn't recommend one type of mask over another, its new guidance emphasizes that N95s and similar high-filtration respirators offer the best protection against COVID-19.

So which respirator is right for you? And where can you buy a legitimate one? And do they have to be uncomfortable?

I've spent a fair amount of time over this pandemic researching masks, calling experts who study them – and fielding questions like these from family and friends. It turns out, it's not that hard to find a good mask that's comfortable to wear for hours. Here's my attempt to answer your questions and break it down for you.

What's the difference between N95s, KN95s, and KF94s? Is one just as good as another?

These are all high-filtration respirators, made with a material that has an electrostatic charge, which uses the power of static electricity to trap incoming virus particles. When worn correctly, they are designed to filter out around 95% or more of airborne particles. (I say "around" because technically, the "94" in a KF94 indicates it has a 94% filtration efficiency.)

All these respirators are a huge step up in protection from a basic cloth mask, but they're not all created equal.

"An N95 is more protective because it has a better face seal in general than a KN95 or a KF94," explains Aaron Collins, a mechanical engineer with a background in aerosols science. He's also known as the Mask Nerd because he's been testing hundreds of masks over the last year and a half. (You can explore a master spreadsheet of his results here.)

Different respirators also attach to your head differently. N95s are strapped to your head with a headband, which gives them a snug fit – and with masks, a tight fit is key to better protection. In its new guidance, the CDC notes that N95s and other NIOSH-approved respirators are the most protective options.

By contrast, both KF94s and KN95s attach with ear loops, which many people find more comfortable but don't seal quite as tightly to your face. As Collins notes, it's a tradeoff: "Are you willing to give up a little bit of protection so that you can quickly take it on and take it off? Or do you want maximum protection, but you're going to have headbands – and if you have long hair, you're going to have to put it in a ponytail to put it on and then let it back down?"

Some American consumers really prefer the flat-fold shape and ear loop attachments of the KN95 – so much so that "one really anomalous thing has happened," says Miller: NIOSH-rated manufacturers in the U.S. have now started making KN95-style masks – a Chinese standard – for sale in the U.S. market. Go figure.

I've heard fake masks can be a problem – how do I know I am getting the real deal?

N95s are made to U.S. government standards put out by the National Institute for Occupational Safety and Health and are rigorously tested, so they're a reliable choice. KF94 is a South Korean standard, and they're regulated by the Korean government. "Every [KF94] I've tested so far has been extremely high performing," Collins says.

KN95 is a Chinese respirator standard, but these respirators aren't strictly regulated by the Chinese government, according to both Collins and Anne Miller of Project N95, a nonprofit organization that connects consumers with legitimate masks and other PPE. While you can find some good KN95s (the ones made by Powecom have done well in tests), low-quality or outright fake KN95s have been a problem throughout the pandemic.

There are some clues to detect fakes. For example, Miller says the front of KN95s are supposed to be stamped with both the company name and the respirator standard number – masks produced as of July 1, 2021, bear the standard number GB2626-2019; masks produced before that date have the standard number GB2626-2006. If your KN95 is missing those things, she says that suggests it's not authentic. As for N95s, here's the CDC's guide for spotting fakes.

But overall, it can be hard to tell if you've got the real deal with any mask, which is why Collins and Miller both say it's important to buy from a trusted source. Project N95 is one option – it vets mask distributors. Collins also recommends Armbrust USA, a company that makes and sells medical-grade masks made in the U.S.A. by various manufacturers.

You can also go to big box stores like Home Depot and Lowes, says Collins. He says shopping for masks on Amazon can be tricky, because vendors change quickly. But if you really want the convenience Amazon offers, he recommends sticking to the official stores of well-known mask brands, like 3M or Kimberly-Clark. "I wouldn't just buy random stuff on Amazon," he says.

One other note: Miller says there are now plenty of U.S.-based manufacturers making NIOSH-rated N95s, so supply is no longer an issue – as the CDC noted in its updated mask guidance. But with surging demand for respirators, she says mask manufacturers and others along the supply chain are having a hard time getting them out the door fast enough. So don't expect your order to arrive overnight.

If you want a South Korean KF94 respirator, Collins says you can try online shops like Be HealthyUSA and Kollecte USA. He says these started out as importers of Korean beauty goods, but now also import KF94 masks, which are extremely common in South Korean drug stores.

NIOSH-approved N95 masks are recommended to prevent the transmission of the COVID-19 omicron variant.

NIOSH-approved N95 masks are recommended to prevent the transmission of the COVID-19 omicron variant. / Jennifer Swanson/NPR

Can I re-use an N95 or other respirator?

Yes, though Miller advises following the "brown bag decontamination method." Basically, if you need to wear a respirator all day for your job, at the end of the day, put it in a brown paper bag or hang it up in a cool, dry place. The idea is to let it rest for five days so any viral particles trapped on it can die off. Label the bags Monday mask, Tuesday mask, etc. The CDC advises reusing an N95 respirator no more than five times. (Health workers shouldn't reuse them.) Using this guideline, a rotation of just five respirators could last you 25 days, Miller notes.

What if you only don an N95 for a quick trip to the store every now and then? Then think about your respirator's total lifespan being about 40 hours of use, Miller advises – the equivalent of five eight-hour days. If the respirator is dirty or getting harder to breathe through, or the straps have gotten stretched out, it's time to toss it out.

One other note: Masks can expire. Miller says a mask can lose some of its particle-trapping electrostatic charge over time, and the headbands or ear loops can lose elasticity – all of which may render it less protective.

She says KN95s typically have a two- or three-year shelf life – check the packaging for a small ticket that will tell you when it was made.

As for N95s? NIOSH doesn't require respirators to be marked with a shelf life date, though some manufacturers will include this information. While it's possible that some expired N95s may still work well, once they're past their shelf life, they're no longer considered NIOSH approved.

NIOSH-approved N95 masks are recommended to prevent the transmission of the COVID-19 omicron variant.

NIOSH-approved N95 masks are recommended to prevent the transmission of the COVID-19 omicron variant. / Jennifer Swanson/NPR

N95s can be really uncomfortable. How do I find one I can wear all day without being miserable?

N95s come in different shapes and sizes these days – Collins' spreadsheet identifies five basic types: bi-fold, boat, cup, cone and duckbill. It may take some time and trial and error to find a good match for you.

For example, I dislike rigid cup-shaped N95s, though Miller says many men prefer that style "for reasons I don't understand." Collins likes tri-fold or boat-shaped N95s like the 3M Aura 9205+, which has foam over the nose clip for added comfort.

He and Miller say N95s with a breathing pocket or duckbill shape tend to fit a large number of people. "These duckbill-style masks – they look a little goofy but it's incredibly breathable. I'm pretty sure you could run a marathon in that thing and not have a problem," says Collins. Kimberly-Clark, 3M and Gerson all make duckbill N95s he likes.

"You've got to kind of find your respirator, which is a weird thing to say these days. But once you do, they're really comfortable," he says.

Don't know where to start? Some companies offer fit kits that contain various N95 styles, so you can try them all to find the best fit.

And remember, the mask does need to fit very snugly – the whole idea is not to let air come in and out around the edge. One way to check is to put on a pair of glasses, or sunglasses. If they fog up, you don't have a good fit. Try tightening up the nose band or straps, or try another style of mask.

What about respirators for kids?

N95s aren't regulated for children, so if a mask says it's an N95 for kids, don't trust it. For child-sized respirators, you have to look at KN95s and KF94s. Collins has tested a bunch of brands – you can find the link to his results for kids' masks here, which also suggests which masks might fit different age ranges best. (Here's Collins' video primer for parents looking for masks for the 12 and under set.)

Older children and teens may be able to wear petite, small or medium-sized N95s.

Kids can be hard to fit, so you might have to try a few different brands to find a respirator that not only fits your child but which they can put on correctly by themselves during the school day.

Full disclosure: I speak from experience – I used Collins' list to find a respirator that worked for my 7-year-old. It took a few tries, but we settled on the WellBefore petite-small KN95 for kids.

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