Upgrade Your Face Mask: 5 Ways To Filter Out More Particles : Shots

Sep 28, 2023

Maria Godoy

This story originally ran in February. It's been updated throughout to reflect new developments and the latest science.

With delta surging and health officials urging indoor mask use in many places, you've likely pulled out your old cloth masks. But it may be time for an upgrade.

"Masks still work, but with delta, we need better-performing masks," says Linsey Marr, a researcher at Virginia Tech who studies airborne virus transmission.

The delta variant transmits more than twice as easily as the original strain of the coronavirus. It's now one of the most contagious respiratory viruses we know of.

And it also replicates quickly in the noses and throats of infected people, so they could be walking around with 1,000 times more virus in their body than with the original strain. All of that means it's imperative that you make sure your mask is protective, and not simply a bedazzled decoration for your face.

So what makes a high-performing mask? Marr says a mask's filtration efficiency is a function of both what material it's made of and how well it seals to your face. So whatever you do, make sure there are no gaps under cheeks or chin where the virus could sneak in.

Read on for more tips on how to seriously boost the protection your face mask offers.

Some public health experts have suggested that the spread of delta calls for donning more seriously protective masks like the gold standard of protection, N95 respirators, which block out at least 95% of particles when worn correctly.

The good news is N95s are plentiful these days. However, they do have a downside. Because they seal so tightly to your face (that's why they work so well), N95s aren't exactly fun to wear, notes Dr. Ibukun Kalu, a pediatric infectious disease physician at Duke Children's Hospital.

"No one wants to wear an N95 for eight hours," Kalu says. She says they're great protection when you are in a high-risk situation such as caring for a COVID-19 patient, "but it can be quite uncomfortable."

If you decide to opt for an N95 anyway, watch out for fakes. Check the CDC's site for advice on how to spot a counterfeit and a list (last updated in June) of trusted sources for surgical N95s. You can also find more guidance on choosing a good fit among different N95 styles, and buy a NIOSH-approved mask at companies like Aiden and the nonprofit Project N95.

Some people have a harder time with the straps that N95s use to attach to your head. In that case, you can also consider KN95 respirators, which often attach with more comfortable ear loops. KN95s are regulated by the Chinese government, and, like N95s, they're supposed to filter out at least 95% of small airborne particles, although the testing standards differ in each country.

However, counterfeits have also been a problem with KN95s. And the FDA recently revoked the emergency use authorization it had granted to KN95s, which allowed them to be used in health care settings. However, you can still search the FDA's list of formerly approved KN95s. You may also want to check NIOSH's list of foreign-made respirators it tested for filtration efficiency in the past, though the agency has now stopped doing those tests.

If you opt for one of these respirators, make sure they also fit tightly to your face. And remember, no matter what you choose, the best mask is ultimately the one you will wear consistently.

Layering a cloth mask on top of a surgical mask helps achieve a tighter fit while also adding an extra layer of filtration. Double-masking like this increases protection against the coronavirus. Michele Abercrombie/NPR hide caption

Layering a cloth mask on top of a surgical mask helps achieve a tighter fit while also adding an extra layer of filtration. Double-masking like this increases protection against the coronavirus.

One good way to get a better mask is to double up, says Marr. Start with a surgical mask closest to your face, she says, and then add a cloth one on top.

The downside of surgical masks is that many of them fit loosely — and a mask's ability to filter out particles depends partly on how well it seals to your face. By layering a cloth mask on top, you can achieve a tighter fit while also adding an extra layer of filtration, says Marr, who co-wrote a commentary earlier this year recommending double-masking.

Choose a surgical mask made out of a nonwoven material called polypropylene, because that material holds an electrostatic charge that allows it to trap particles. (Some surgical masks are made of paper.) Then add a good quality cloth mask.

But don't keep piling on masks, Marr warns; just one additional mask is plenty. If your masks become too hard to breathe through, air will leak in and out through the sides instead. "Then it's like you have a hole in your mask," Marr told NPR earlier this year.

Tie the ear loops close to the edges of the mask and tuck in the side pleats to minimizes gaps (left). Or use a hair clip to hold the ear loops tightly at the back of the head to achieve a tighter seal. Michele Abercrombie/NPR hide caption

Tie the ear loops close to the edges of the mask and tuck in the side pleats to minimizes gaps (left). Or use a hair clip to hold the ear loops tightly at the back of the head to achieve a tighter seal.

Even at this late stage in the pandemic, it still bears repeating: Don't let your nose hang over your mask – that defeats the purpose! And to get the best protection, you also need to make sure that your mask fits as snugly as possible over your mouth and nostrils, up to your nose bridge and that you don't see any gaps.

A mask's filtration efficiency varies depending on how well it conforms to your face, as a study in JAMA Internal Medicine illustrates. Researchers found that the surgical masks they tested blocked out just 38.5% of small particles on average when worn normally. But filtration efficiency jumped when they tried various hacks to make the mask seal better.

One trick they tested: Tie the ear loops into a knot as close to the edges of the mask as possible, then tuck the side pleats in to minimize any gaps that appear along the edges, as in the left photo, below. This boosted the surgical mask's filtration efficiency to 60%.

Another simple hack is to use a hair clip, as in the photo above at right to hold the ear loops tightly at the back of the head. That raised the mask's filtration efficiency to nearly 65%.

You could also try a mask fitter or brace — an elastic frame that fits over a mask to make it seal more tightly to the wearer's nose, mouth and face. One study from researchers at the University of Wisconsin-Madison found that using a mask fitter enhanced a surgical mask's filtration efficiency from under 20% to over 90%.

"That shows you how important the fit is and how good a surgical mask can be if you are able to eliminate the leaks," notes Marr.

To test if your mask fits well, try wearing it with glasses, suggests Jamie Weaver, a research chemist at the National Institute of Standards and Technology who has been studying the filtration efficiencies of mask materials. "If you start fogging up your glasses, that's a sign of a leak. I've also seen people put little hand mirrors next to the edge of their masks and breathe and see if they fog up mirrors."

You can achieve a boost in filtration efficiency by wearing a two-layer mask with a pocket for a filter. Insert a surgical mask or a carbon filter in that pocket. Michele Abercrombie/NPR hide caption

You can boost filtration efficiency by wearing a two-layer mask with a pocket where you can insert a filter. The outer layers should be made of a tight-weave fabric.

Marr suggests using a surgical mask in the filter pocket. (You can cut the surgical mask to fit the pocket if need be.) She says HEPA filters cut out from the filters used in portable air cleaners work very well (here's her how-to video). You can also buy fabric masks with a filter layer permanently attached.

Another filter option: a material available at fabric stores called spunbond, also sold under the brand name Oly-Fun. It's made out of polypropylene, so it also uses the power of static electricity to trap particles. Adding a filter made out of two layers of polypropylene could boost a cotton mask's filtration efficiency by as much as 35%, Stanford University researcher Yi Cui told NPR last year.

When it comes to mask filters, "the size of the filter seems to matter," says Weaver, who co-authored a recent study on the topic in the journal ACSNano. Choose a filter that spans the material of your cloth mask, Weaver says — and make sure it's breathable.

For a cloth mask, in general, you want to look for a fabric with a tight weave. Multiple studies have shown that 100% cotton is a good bet (think slightly stiffer dress-shirt cotton). Michele Abercrombie/NPR hide caption

For a cloth mask, in general, you want to look for a fabric with a tight weave. Multiple studies have shown that 100% cotton is a good bet (think slightly stiffer dress-shirt cotton).

If you're sticking with a cloth mask, make sure the one you wear is as protective as it can be. Opt for at least two layers in your mask — three layers are even better: Studies have shown that a three-layer mask made from tightly woven cotton fabric works well.

Look for fabrics that don't let light pass through when held up to a light source. (Think slightly stiffer dress-shirt cotton rather than thin T-shirt cotton.)

One excellent choice: cotton flannel, says Weaver. She and her colleagues have found that a two-layer cotton flannel mask's filtration efficiency jumped by an average of 33% when it becomes humid — the kind of conditions created when you're breathing into the mask.

Synthetic fibers didn't perform as well, and they saw no boost from humidity. Perhaps not surprisingly given these findings, Weaver says her go-to mask of choice is a homemade multi-layer cotton flannel mask.

As Christopher Zangmeister, a researcher at NIST, explained to NPR last year, tightly woven natural cotton fibers with a raised nap, like flannel, tend to have more three-dimensional structure than synthetic fibers. That can create more roadblocks to stop an incoming particle. That said, filtration tests have shown that some masks made of other fabrics, like an engineered knit, can be highly effective.

NPR's Rob Stein contributed to this report.