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Two masks may provide greater protection from the spread of the novel coronavirus, but experts say it depends on the quality of the masks and the way they’re worn. Miquel Llonch/Stocksy United
  • Dr. Anthony Fauci has said that double masking “just makes common sense.”
  • In theory, it’ll help reduce the spread of COVID-19 by filtering more particles.
  • Double masking is most helpful when there are concerns about source control.

All data and statistics are based on publicly available data at the time of publication. Some information may be out of date.

On a recent appearance on the “Today” show, Dr. Anthony Fauci, who is the chief medical adviser on COVID-19 for the president, said that double masking is a move that “just makes common sense” and is “likely” to provide more protection against the transmission of COVID-19.

In addition, high profile figures like transportation secretary Pete Buttigieg and his husband, Chasten, have been spotted wearing double masks in recent weeks.

Is double masking a good idea for you? When and how should you go about doing it?

Here’s what we currently know.

According to Firas Zabaneh, MT (ASCP), CIC, CIE, director of system infection prevention and control for Houston Methodist Hospital in Houston, Texas, double masking might help.

Zabaneh said the rationalization for wearing two masks is that you’re adding more layers of filtration.

Filtration efficiency is increased, Zabaneh said, so fewer particles penetrate through the masks.

However, he cautions that wearing two masks may give people a false sense of security.

If a person is wearing two low quality masks on top of each other, it may not be very effective.

In addition, if not done properly, wearing two masks could actually increase a person’s risk by allowing leakage around the edges.

Binghamton University mechanical engineering assistant professor Scott Schiffres, PhD, who’s been working on testing masks since the COVID-19 pandemic began, said that increasing protection isn’t just about adding more layers of filtration.

If the masks are worn in a way that compromises the fit of the masks on the face, this may allow unfiltered air to leak through gaps.

For example, wearing two surgical masks won’t be better than one, Schiffres said.

“It is not the ability of the filter that limits performance,” he said, “but the fit to the face (how much air leaks at the face seal).”

“The surgical mask material itself is very good (>95 percent at 0.1 um), but in practice about 20 percent of the air will slip between the mask and the seal of the mask, so the efficiency would effectively be about 80 percent,” Schiffres said.

“If you were to just put two surgical masks one on top of another, more of the air would actually leak around the seal as the resistance through the masks increases, and even less air would be filtered, making this double masking detrimental,” he said.

“The most important thing,” Schiffres said, “is not to have a false sense of confidence in the filtration of the mask, as it can only be as good as the fit to your face allows.”

The Centers for Disease Control and Prevention (CDC) released a report on Feb. 10 outlining two methods that have been studied as a way to improve the fit of medical procedure masks.

One way involves knotting the ear loops of a medical mask and then tucking in and flattening any extra material so the mask fits closer to the face.

The other involves double masking by wearing a cloth mask over a medical procedure mask.

In an experiment, the CDC simulated what would happen when a person coughs when they and another person in their proximity are wearing various mask combinations.

The combinations included: no mask, a 3-ply medical mask alone, a cloth mask alone, double masks, unknotted mask, and knotted and tucked medical mask.

Altogether, 10 different combinations were tested.

They found that the unknotted medical mask alone blocked 40.2 percent of particles from the simulated cough, while the cloth mask alone blocked 44.3 percent.

However, when the two were combined, with the cloth mask over the medical mask, the particles blocked jumped to 92.5 percent.

In a second experiment, researchers found that adding a cloth mask over a medical mask reduced the exposure of the receiver by 82.2 percent.

In addition, knotting and tucking a medical mask reduced this exposure by 62.9 percent.

When the source of the cough was unmasked, but the receiver was wearing a double mask or a tucked medical mask, the receiver’s exposure was reduced 83 percent and 64.5 percent respectively.

The best results, however, were obtained when both the source and receiver were double masked or wearing knotted and tucked medical masks.

The exposure of the receiver was reduced 96.4 percent with double masking and 95.9 percent with knotted and tucked masks.

Zabaneh said that one case in which it’s a good idea to wear double masks is when there are concerns about source control.

“For source control purposes, anyone who is wearing a mask with an exhalation valve (including N95 respirators with exhalation valves) should apply a secondary mask on top of the primary one,” he said.

“This is intended to provide protection for others if the wearer of the mask with the exhalation valve is infected with SARS-CoV-2.”

In addition, the CDC is now recommending double masking as a way to improve mask fit and reduce the spread of COVID-19.

According to the CDC report, wearing a cloth mask over a medical mask can provide “substantially improved source control” as well as reducing exposure of the wearer.

Zabaneh suggests that if you double mask, you should choose a good quality mask that maximizes filtration.

It should be constructed in such a way that it creates a good seal on your face so that unfiltered air doesn’t leak around the mask.

In addition, you should be aware that double masking can potentially make it more difficult to breathe.

More layers of filtering materials means more resistance to air flow, Zabaneh said.

He suggests looking for masks that filter well and provide a good seal without inhibiting your breathing too much.

“There are many such masks on the market at this time,” Zabaneh said.