CDC study backs mask doubling with exposure to risky particles down 83%

[Karlston]

CDC study backs mask doubling with exposure to risky particles down 83%

Data has lots of caveats, but it's not a bad idea to up your mask game.

Enlarge / Self-sewn protective face masks in a fabric store on April 3, 2020, in Jena, Germany.

Getty | Jens Schlueter

 

With the pandemic still raging and several dangerous variants looming, many experts have suggested doubling up on masks. Now, a new study by the Centers for Disease Control and Prevention doubles down on that strategy.

 

Adding a cloth mask over a surgical mask on a rubbery dummy head more than doubled particle blocking when the dummy simulated coughing—aka spewing particles capable of carrying coronavirus—the study found. Specifically, a surgical mask or a cloth mask alone blocked about 42 to 44 percent of particles, respectively, coming out of the coughing dummy. The combo of a cloth mask over a surgical mask blocked 92.5 percent of the risky particles.

 

Next, the CDC researchers gave the rubbery dummy head an equally disembodied friend, spaced about two meters (six feet) away in a cozy, unventilated experimental chamber. When one of the heads quietly belched aerosol particles (source) while maskless, the researchers measured the dose of particles that the companion (receiver) took in during a 15-minute period. Wearing a surgical mask alone cut the receivers’ exposure to particles by just 7.5 percent, compared to wearing no mask. Wearing a double mask cut the exposure by 83 percent.

 

Then, the researchers flipped the scenario by trying out masks on the source and leaving the receiver maskless. A surgical mask alone on the source cut the maskless receiver’s exposure about 41 percent. When the source wore a double mask, the maskless receiver’s exposure dropped to 82 percent.

 

When both the source and the receiver wore double masks, the receiver’s exposure dropped to 96 percent.

Enlarge / Masks tested, including A, unknotted medical procedure mask; B, double mask (cloth mask covering medical procedure mask); and C, knotted/tucked medical procedure mask.

CDC

Last, the researchers also tested out tucking and knotting a surgical mask on either the receiver or the source head. The tuck-and-knot reduces side gaps that let unfiltered-breath escape. This alone reduced the receiver’s exposure by 64.5 percent and 63 percent when it was used by the receiver or the source, respectively. When both heads had tucked-and-knotted masks, exposure dropped again by 96 percent.

Conclusions and cautions

“These laboratory-based experiments highlight the importance of good fit to maximize overall mask performance,” the researchers concluded. The agency’s researchers also noted the potential benefits of using other mask-tightening methods, such as using sheer-nylon hosiery around your mask or a mask-fitter product to keep masks tighter around your face.

 

Let’s note some important caveats, though. The researchers emphasize that they were mainly looking at relative improvements in mask performance. The agency only tested one example of each mask type (surgical and cloth) and one type of combination—cloth over surgical mask. There is a plethora of mask options out there and ways to combine each one. It’s also unclear how the double-mask method used in the study would stack up to more stringent mask designs, such as the one outlined by the World Health Organization. That’s all to say that your specific results may vary. Last, another obvious limitation is that the researchers were using rubber heads, not the real ones.

 

“The findings of these simulations should neither be generalized to the effectiveness of all medical procedure [surgical] masks or cloths masks nor interpreted as being representative of the effectiveness of these masks when worn in real-world settings,” the researchers caution.

 

And, in the broader context of the threat of more infectious variants—it’s still unclear how much upping your mask game will help. So far, standard mask wearing and the other usual protective measures—physical distancing, avoiding crowds and poorly ventilated indoor spaces, and good hand hygiene—appear to remain effective against the variants. Still, as many experts have been saying recently, improving mask performance likely can’t hurt.

 

 

CDC study backs mask doubling with exposure to risky particles down 83%

[Karlston]

How to Double Mask

The CDC has released a report showing that two masks are better than one for curbing transmission of the coronavirus. Here's the proper way to double up.

Photograph: Kena Betancur/Getty Images

This week, the US Centers for Disease Control and Prevention released findings that double-masking—wearing one face mask on top of the other—can be an effective way to reduce the transmission of the coronavirus that causes Covid-19. It’s a practice experts have been mulling over for a while now, with President Biden’s chief medical adviser Anthony Fauci advocating for double-masking back in January. Now the CDC’s lab tests show that double masks can reduce the likelihood of coronavirus transmission between two people by up to 95 percent if both parties wear them correctly.

 

Now that masks are (finally!) required on public transportation and federal premises, the CDC has updated its mask guidelines to include advice on double-masking. Here’s how to make sure you get a snug fit.

 

Double Up

 

Start with a disposable medical or N95 mask underneath. Then add a cloth mask over the top. As with any mask you wear, the most important thing is making sure both masks have a proper fit. Both masks should be covering both your nose and mouth. Ideally, the inner medical mask will have a nose wire to make a proper seal against your nose, and the cloth mask will press the inner mask closer to your face and ensure a tighter fit.

 

Try blowing out a big breath while you feel around the edges of the mask stack. If any of your hot air is escaping, adjust the mask until there’s a sealed fit all around the sides. Try to use a mask with a nose wire, as they do a much better job of forming a seal around your nose and mouth.

 

In general, if the mask just isn’t working, or you find yourself constantly adjusting it, it might be time to try a different brand or fit.

 

All About That Fit

 

The report released by the CDC this week wasn’t just about double-masking. It also reported findings about the efficiency of a technique for medical masks known as knotting and tucking.

 

Disposable masks are designed to stop the aerosol particles coming out of the wearer’s mouth, and also protect from splashes. They aren’t designed to offer a perfect seal, which means the sides tend to hang loose and open. That’s bad news if you’re trying to block a virus that can be transmitted through the air.

 

According to the CDC’s findings, tucking those sides in can greatly reduce the chance of exposure. To do that, fold the mask in half so that the top edge meets the bottom edge. Then tie a knot in each of the ear loops, keeping the knot as close as possible to the spot down where the strings connect to the mask. After tying both knots, take the excess fabric bunched up on the sides of the mask and tuck it inside the mask. Be sure there aren’t any gaps next to the knots where air can pass in and out. Lastly, try on the mask to be sure that the mask still provides the proper coverage from your nose down to your chin. The technique is a bit tricky to describe, so here’s a short video that demonstrates it.

 

Human Shield

 

Whether it’s knotting or double-masking, there are some important caveats to note here. First is that all of the CDC’s testing was done by pairing 3-ply cloth masks with medical masks—the agency made no claims about stacking two cloth masks. It also recommends against double masking with two disposable masks, as wearing two of them won’t make them fit better. Also, these methods weren’t tested with children or people with beards or other facial hair. Smaller and/or hairier faces will take some extra doing to create a proper fit. (Side note: Our picks for best kids’ masks are here. Sorry beardos, you might just have to shave it already.) And when you're done with your disposable mask, be sure to get rid of it properly. It goes into the trash can, not into the recycling bin or onto the ground.

 

Even though double-masking may provide more protection from Covid exposure, it’s not a substitute for other pandemic precautions. The CDC performed its tests in a lab by simulating a coughing person (or “pliable elastomeric headform,” as they hilariously call it) so it isn’t a perfect analogue for a real human. So stay diligent. Keep avoiding crowds, stay 6 feet apart, and keep your mask on in public, even when outside.

 

The CDC’s guide to improving mask fit is here. Check out our favorite cloth masks here.

 

 

How to Double Mask