Coronavirus FAQ: Why Am I Suddenly Hearing So Much About KF94 Masks?

Each week, we answer "frequently asked questions" about life during the coronavirus crisis. If you have a question you'd like us to consider for a future post, email us at goatsandsoda@npr.org with the subject line: "Weekly Coronavirus Questions."

Nearly a year into the pandemic, the most talked about piece of apparel is an item that folks barely even thought about back in the early days of 2020.

Yes, we're talking about masks.

They come in all shapes and sizes, and you've probably got your preference. Some are scratchy; some are soft. There's cotton and polyester, the standard ear-loop model and sleek neck gaiters. Not to mention the designer mask Jill Biden wore that matched her sparkling blue inaugural coat.

And, of course, there's the ever-ubiquitous pastel blue surgical mask – a fan-favorite, I daresay, based on how many are seen lying around on city streets.

Plus your good-ol' KN95 — the medical-caliber mask that is still in short supply and reserved for health workers.

Now, add another player to the mix – the KF94. This mask had been getting increasing buzz these days, with at least one media outlet calling them a "highly protective" option to look into at a time when emerging coronavirus variants appear to be more contagious.

So — what's the deal with the KF94?

As Stephen Morse, an epidemiology professor at Columbia University, puts it, a KF94 is essentially the South Korean equivalent of the N95. They're "pretty comparable," he says. For a visual image, you can think of a mash between an N95 and a typical cloth mask. The KF94 comes with side flaps, which mold to the contour of your face, and an adjustable band around the bridge of your nose.

To understand how it works, all you have to do is investigate those mysterious initials.

Sonali Advani, an assistant professor of medicine at Duke University, explains that KF stands for "Korean filter." And 94 refers to its filtration efficiency (basically, just how good the mask is at filtering out particles we don't like), which is 94%. Non-surprisingly, then, an N95's filtration efficiency is 95%.

A limited study published last year showed that the KF94 was comparable to the N95 in blocking SARS-CoV-2 particles.

But Advani doesn't think the KF94 is a game changer. "While there are minor differences, those differences are rather small in general," Advani explains. "It's negligible."

But they are easy to come by. Says Morse: "KF94's seem to be more readily available than the N95, less expensive [generally under $2 each] and easier to use for many people," Morse explains. "KF94 is actually intended for public use. In Korea they are often worn by ordinary citizens to filter out dust or pollution."

But is the KF94 really more protective than other consumer options?

"When it comes to use in day-to-day activities, overall surgical masks and three-layered cloth masks perform pretty well," Advani emphasizes. As far as protection goes, masks with multiple layers will do you better in staving off potentially infectious particles than thin ones – and studies have shown that 3 layers is typically the sweet spot.

In other words, she says, there's no need to buy up medical grade KF94s — especially, she says, since some wearers have said the South Korean mask is less comfortable or harder to breathe out of than the alternatives.

Of course, this is all subjective — so you'd have to try one yourself.

The bottom line is this: "It's not always just about filtration efficiency," Advani says. "While these masks [like the KF94] may be better for use in a hospital [because they're designed for medical settings}, in the real world, it may be the case that they are hard to wear through the course of the whole day. And the best mask is the one you can wear all the time."

What's most important, she emphasizes, is compliance with existing mask guidelines — and re-committing to earnest and consistent mask wearing.

If you do end up choosing to invest in a KF94 mask, Morse warns to be wary of counterfeits.

"Not all KF94 masks are made in Korea — many are manufactured in China — (but) KF94s manufactured in Korea may be less prone to counterfeiting," he says.

Or you can use a quick, expert-approved trick to test the mask's effectiveness. Try blowing out a candle while you've got it on. If you can't, you're probably good to go!

Pranav Baskar is a freelance journalist who regularly answers coronavirus FAQs for NPR. [Copyright 2021 NPR]