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PolitiFact: Are homemade masks effective against coronavirus?

Their efficacy depends on what kind of material they’re made of and how they’re used.

Since the beginning of the COVID-19 outbreak, public health officials have advised healthy Americans not to wear face masks. The reason: There’s a shortage of masks, and they should be reserved for health care workers.

That guidance may change soon.

"When we get in a situation where we have enough masks, I believe there will be some very serious consideration about more broadening this recommendation of using masks," said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, on CNN March 31. "We're not there yet, but I think we're close to coming to some determination."

One of the best ways Americans can avoid infecting others — even if they aren’t showing any coronavirus symptoms — is to wear a surgical mask when they’re out in public, Fauci said. But with shortages around the country, it’s hard for even health care workers to get them.

So some people have started to make their own. Homemade masks have become so popular that there are Facebook groups where avid sewers coordinate their efforts to provide protection for health care providers. Some hospitals are asking for homemade masks, while others won’t let their employees wear them while treating COVID-19 patients.

Several readers asked PolitiFact whether DIY masks are as effective at preventing the transmission of COVID-19 as the surgical ones. So we read the latest research and talked to experts.

We found that, while homemade face masks can serve as a potential alternative to surgical masks, they don’t offer the same level of protection. And their efficacy depends on what kind of material they’re made of and how they’re used.

First, let’s clear up how they work.

Face masks do not block some very fine particles in the air that may be transmitted by coughs or sneezes. That means they’re not a reliable way of preventing someone who’s wearing one from contracting the airborne coronavirus particles and getting COVID. But, since masks do prevent the spread of larger respiratory droplets, they are effective at preventing someone from spreading the virus to other people.

In its guidance to health care providers, the CDC says homemade masks like bandanas and scarves can be used as a last resort. Since their ability to protect against the coronavirus is unknown, the agency recommends that providers use them in combination with face shields and other protective equipment.

Some health care providers are using homemade masks so that they can prolong the lifespan of the masks they do have, including the N95 respirators that filter out at least 95 percent of airborne particles.

"Some hospitals are creating masks, using homemade ones, that can be worn on top of the N95 masks," said Anna Adams, vice president of government relations at the Georgia Hospital Association. "The outer ones are washable, and that extends the life of N95."

Some hospitals have already started to run out of N95 respirators, and the CDC does not advise the American public to use them as a COVID-19 prevention measure. The current advisory says people infected with COVID-19 or living with someone who is should wear generic surgical masks.

Given the shortage of those face masks around the country, DIY masks could be effective at preventing the spread of the coronavirus. But they have to be made correctly.

The most effective homemade masks are made of thick cloth and make a tight seal around the wearer’s face.

"Given the current crisis, and lacking an alternative, many layers of densely woven fabric would be the most effective, because it allows for lots of voids in the layers where particles can be trapped," Richard Peltier, an assistant professor of environmental health sciences at the University of Massachusetts-Amherst, told us by email. "The mask needs to seal as tightly as possible to the face to avoid leaks, though this may not be possible with different designs, fabrics, or face shapes. Thin or porous fabrics are the least likely to be effective."

A study published in October 2010 tested how cloth masks and common fabrics fared when sprayed with aerosols at different speeds. All of the materials performed worse than N95 respirators. But some, such as cotton towels and scarves, were in the range of some surgical masks. The authors cautioned that fabric materials "show only marginal filtration performance against virus-size particles when sealed around the edges."

Another study from 2013 found that cotton masks only perform about half as well as surgical masks and "should only be considered as a last resort to prevent droplet transmission from infected individuals." More recent research had similar results.

So at best, using thick or layered fabric to make a homemade mask could be as effective as using some surgical masks. At worst, it prevents at least some of your respiratory droplets from spreading to others while in public.

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Under ideal circumstances, no face masks are intended to be worn for more than one encounter. That guidance also extends to homemade masks.

"At the end of the day, these cloth masks should be treated as contaminated materials that you bring in to your home — they need to be laundered in hot soapy water, and you’d need to consider sanitizing in bleach or hydrogen peroxide regularly," Peltier said.

Some experts have said face masks could also serve as a reminder to not touch your face, which is one of the ways the coronavirus spreads, according to the CDC. But Peltier said he’s not aware of any research that shows that’s the case. And there’s a chance that masks could actually encourage people to touch their face more since they can be uncomfortable to wear.

Still, since those infected with the coronavirus may not exhibit symptoms for up to 14 days after exposure, the CDC may soon advise everyone to wear masks in public just in case they’re sick. In that case, if you’re going out in public, wearing something is better than nothing.

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