Are Two Better Than One? Expert Weighs in on Double Masking


Updated 2/12/2021 with new CDC Guidance

Ever since Dr. Fauci said he often double masks and that two masks “just makes common sense,” the medical community has been in somewhat of a debate with many in agreement, and some saying the opposite.

BioSpace reached out to Dr. Andrea Love, immunologist, microbiologist and co-host of a weekly podcast called Unbiased Science. Love shared her take.

“In light of the new COVID-19 variants which are estimated to be at least 50% more transmissible, it is imperative that we must be more vigilant than ever,” Love said. “With a more transmissible virus, that means every exposure has increased likelihood of leading to spread. We must be more stringent with our behaviors now, including social distancing, minimizing trips to public places, avoiding indoor spaces, and ALWAYS wear a mask. But, not just any mask will do – quality matters.”

According to Johns Hopkins, while the mutations found so far do appear to bind more tightly to our cells, making them “stickier,” the good news is that they are not necessarily more dangerous.

Additionally, the variants have not appeared to affect children more frequently than the earlier strains. In areas of new strain outbreak, kids are being infected by old variants, as well as the new ones.

While going out in public to see every person wearing a mask was novel last spring, mask wearing has become old hat at this point. They’re generally understood to be helpful in slowing down the spread of the disease by providing a physical barrier to block small respiratory droplets containing the virus.

More effective barriers provide less opportunities for droplets to get through.

Love compares the mask layers to a maze.

“The more convoluted the maze is, the more droplets you will trap and prevent from escaping to the environment,” Love said.

This is where layering starts to make “common sense.” More layers = less droplets escaping = more protection. This leaves many questions around mask type, as the market is now saturated with face covering options. Even Walmart is selling kids’ sweatshirts with a matching mask as a fashion accessory.

“N95 masks are the gold standard—but they can be hard to find, expensive and tend to be recommended for frontline healthcare workers,” Love said. “Some alternative KN95 and KF94 masks have been tested and granted EUA by the FDA for being as protective as N95. But check the approved brands – counterfeit options are circulating which have poor protective abilities.”

If one of these brands isn’t available to you, experts say layering a cloth mask on top of a surgical mask can mimic the filter-cloth combo studies have found to be more protective. The cloth layer also helps improve the fit of the surgical mask, pushing down the edges for more of a seal.

Dr. Michael Osterholm, who leads the Center for Infectious Disease Research and Policy at the University of Minnesota, compared mask fit to that of underwater goggles.

"How well does [the mask] fit around you? It's like swimming goggles. They don't usually leak through the lenses, they leak through the seal around your eyes or face," Osterholm said.

Overall, Osterholm isn’t a fan of double masking. He believes it could do more harm than good by blowing air in and out along the sides, thereby becoming less effective.

However, studies have shown that a three-layer face mask consisting of outer layers of a flexible, tightly woven fabric and an inner layer consisting of a material designed to filter out particles blocked more than 70% of the smallest particles and more than 90% for particles 1 μm and larger if the mask fits well.

“A high-quality 3-ply surgical mask or a fabric mask of at least two layers with a high thread count will offer basic protection for the public, when risk is low, such as when you're outside with not many people around,” Love said. “In those instances, a single mask of reasonable quality will suffice.”

Love continued.

“The more physical barriers implemented, the more of these droplets you can block, thereby reducing the risk to yourself and others around you. Ideally, the more layers the better, so even if you have two flimsier cloth masks, that offers more protection than one by itself.”

If you’re worried about not getting enough oxygen, Love said you needn’t be. In individuals 65 and older, a study proved that the use of a 3-layer mask did not lower oxygen saturation. Another study proved that wearing a cloth or disposable surgical mask during vigorous exercise had “no discernable detrimental effect on blood or muscle oxygenation and exercise performance in young, healthy participants.”

Update: The CDC officially released results of their studies regarding ways of improving the efficacy of your mask. As Dr. Love pointed out, mask fit is essential. The CDC found that exposure to infectious aerosols were decreased by 95% when a tightly fitted mask was used. Variations to improve fit included: a cloth mask placed over a surgical mask to improve fit (double-masking), knotted ear loops and tucked in sides on a surgical mask. They also found mask fitters and a nylon covering over mask to be effective. 

The report concluded, "Controlling SARS-CoV-2 transmission is critical not only to reduce the widespread effects of the COVID-19 pandemic on human health and the economy but also to slow viral evolution and the emergence of variants that could alter transmission dynamics or affect the usefulness of diagnostics, therapeutics, and vaccines. Until vaccine-induced population immunity is achieved, universal masking is a highly effective means to slow the spread of SARS-CoV-2 when combined with other protective measures, such as physical distancing, avoiding crowds and poorly ventilated indoor spaces, and good hand hygiene. The data in this report underscore the finding that good fit can increase overall mask efficiency. Multiple simple ways to improve fit have been demonstrated to be effective. Continued innovative efforts to improve the fit of cloth and medical procedure masks to enhance their performance merit attention."

So bottom line from the experts is – keep wearing your mask. Find one that fits you well. And, in poorly ventilated indoor spaces, you might even want to wear two.

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