We asked 13 public health experts whether they double-mask. None of them do.

• Insider asked 13 leading public health experts what they're doing in the face of new variants. None are double-masking.
• Experts stress mask fit, layers, and fabric quality are the most important factors to consider in personal protection.
• Double-masking can be a good solution if you have one high-quality mask that you want to keep protected, or if you want a tighter fit than one mask provides.

The coronavirus is changing, and changing fast.

With several new, possibly more contagious variants on the loose worldwide, experts told us they are clamping down on their own virus precautions: shortening trips to the grocery store, canceling flights, and avoiding crowds now more than ever.

But while Dr. Anthony Fauci has said it's "common sense" for people to double-mask right now, most experts say they're not changing how they mask.

"If you've got a decent mask, then the thing you need is something that's going to make it seal around your nose and your cheeks, under your chin," University of Maryland virologist Don Milton told Insider. "The best thing is to get one that fits."

Insider surveyed Milton, along with a dozen other leading public health experts, including doctors, virologists, mask-makers, and environmental engineers. None of them said they are double-masking right now, but that doesn't mean you shouldn't. Double-masking can still be useful, especially if you don't have a mask that filters or fits well.

Mask fit, fabric, and layering are key

Dr. Anthony Fauci, the US' leading infectious disease expert, likes to wear two cloth masks, because he says it's "more firm and comfortable" than just one, but he says that's not a choice influenced by rigorous scientific evidence.

"There is no scientific study that I know of," Fauci told the New York Press Club on Friday, clarifying that his stance on double-masking is a personal one, and not a professional recommendation.

Read more: Fauci said it is 'common sense' to wear 2 masks to stop the spread of COVID-19. Here's how to do it.

Just because Fauci likes to double-mask doesn't mean you have to. Many masks on the market are multi-layered, and include filters or special fabrics to trap virus particles inside, making them highly effective.

Double-masking is not always practical, either. Dr. Karen Landers, assistant state health officer at the Alabama Department of Public Health, experimented with double-masking: wearing a cotton mask on top of a surgical mask (which is the way that most experts would recommend) - but it didn't go smoothly.

"By the time I adjusted it, and accounted for bunching, and for the difficulty of really keeping it positioned in place, I decided that if I had trouble doing it, that perhaps this was not a good strategy to advise the general public," Landers said.

This is why Landers stresses that wearing one mask that fits correctly is better than wearing two masks.

"If we start going into a strategy of wearing two masks, that is really not, in my opinion, better than wearing an appropriately constructed, layered mask that is correctly fitted and consistently worn."

Many cloth masks are made with two to four layers of fabric, and most surgical masks are built with an electrostatically charged layer, which is designed to trap infectious particles before they reach your face.

Every face mask worn in public should have two layers

The US Centers for Disease Control and Prevention recommends that every face covering worn in public should include at least two layers. There's no reason that a double-mask, made from two single pieces of cotton, would be better than one surgical mask that's fitted properly around your head, or a multi-layer fabric mask with a filter inside.

When professor Linsey Marr, a leading expert on ventilation and viral transmission at Virginia Tech, goes to the grocery store, she wears a cloth mask with a special pocket for HEPA filters that trap small particles. Marr keeps a spare surgical mask and brace in her bag as backup, but she doesn't put two masks on her face at once.

Milton wears a heavy-duty Envomask N95 when he goes into the grocery store, but for more casual strolls around his uncrowded, suburban neighborhood, he likes to use a medical-grade surgical mask (like an Armbrust or a Zubrex). He has even lab-tested these solutions at work and found they perform about as well as N95s in fit tests.

"That doesn't mean they'll fit you, but they fit me," he said. "Everybody's face is a little different."

Other experts said expecting people to wear two masks is simply unrealistic.

"To tell people you have to wear two masks now just seems like an unreachable goal for some," Dr. Peter Chin-Hong, associate dean for regional campuses at the University of San Francisco, California said. "I'm worried that some people just say 'well, I can't do that so I'm just going to, you know, maybe not wear anything.'"

Double-masking can be a good option, especially if you have one high-quality mask that you want to protect

Dr. Jake Deutsch, cofounder and clinical director of Cure Urgent Care Centers, said he doesn't wear two masks because he has COVID-19 antibodies from a previous infection, and has been vaccinated. As a result, he's not that worried about catching or spreading the virus.

He still says he sees the value in double-masking, especially in areas with high case counts. "There is this benefit of having more barriers," he said.

Dr. Daniel Burnett, the CEO of JustAir respirators, who also teaches bioengineering at the University of California, San Francisco, agreed that double-masking can be useful, especially if you're trying to preserve a single higher-quality mask, like an N95, for high-risk encounters like a crowded bus ride or carpool.

"The benefits of a double mask are limited mostly to protecting the inner mask, and potentially better fit of the mask, because now you have two sets of masks anchoring themselves and securing themselves on your face," he said. "So, you can get a better seal."

How to double-mask properly

Experts recommend either a cloth mask on top of a surgical mask or KN95, or else two multi-layer cotton masks.

Whichever way you decide to mask up, make sure your mask fits your face well, and doesn't slip off your nose.

"We happen to know that the stuff in your nose looks like it's very infectious, and the stuff in your mouth is not so much," Milton said. "The main thing you've got to worry about is getting it tight."

For some, that may mean donning a second mask. For others, adding a brace, or switching to a multi-layer mask may be the best answer.