Which Works Better: A Mask Brace Or Double-Masking?

Wearing a face mask to slow the spread of Covid-19 has become common practice.

But some people still wear masks incorrectly or use one that doesn't properly fit their face, which lets aerosols that carry Coronavirus particles leak out.

One solution to that problem is 'double-masking' — wearing two masks at once. Another is using a 'fitter' or brace to secure a mask more snugly to your face. Both approaches aim to prevent air from escaping around the edge of a mask and force tiny droplets to be blocked by the material, which serves as a filter.

What's the scientific evidence that double-masking and mask braces stop air leaking? Which approach is best? And how do they compare with N95 respirators that filter 95% of airborne particles?

Double-Masking

In February 2021, the Centers for Disease Control updated its guidance on effective masks, which now includes the recommendation that people 'add layers of material to a mask'. The agency suggests either using a cloth mask with multiple layers of fabric or wearing a disposable mask underneath the cloth mask.

When asked about double-masking on 25 January, the President's Chief Medical Advisor and director of the US National Institute of Allergy and Infectious Diseases, Anthony Fauci, said it's "common sense that it would be more effective." Common sense isn't science though.

To date, only one study has tested the effectiveness of double-masking. Led by CDC epidemiologist John Brooks, the experiment involved measuring the amount of particles that reached a dummy head from a simulated cough, which showed that a double-mask combination blocked over 85% of particles, compared to 56% and 51% respectively for the surgical ('medical procedure') mask and cloth mask alone.

The study was published in CDC's own digest, Morbidity and Mortality Weekly Report, which isn't peer-reviewed by external researchers. So while the results seem conclusive, the research would have had greater credibility if it had been submitted to an independent journal and/or a preprint server like medRxiv.

Mask Brace

Several studies support the hypothesis that modifications like braces/fitters enhance the effectiveness of filtering.

One paper, published in JAMA Internal Medicine and led by biologist Phillip Clapp, measured efficiencies of masks and improvized face coverings. It showed that modifications enhanced the filtration of surgical masks from 39% to 80%.

Another recent study (unpublished but in medRxiv) used salt to mimic aerosol transmission inside a classroom and equations to estimate the risk of infection for teachers and students. Led by mechanical engineer David Rothamer, the study found that most masks fit poorly and allowed over 50% leakage, but braces can bring a mask's filtration efficiency back up to its expected performance level.

Consumers can buy a special mask brace, but they're relatively expensive: for example, Fix the Mask sell a two-pack of silicone braces (designed by a former Apple engineer) for $30. The company offers a downloadable template for making a DIY brace from a rubber sheet... if you have such material around your house.

But you can make a brace on a budget, from three rubber bands and a paperclip, as demonstrated by doctors led by Daniel Runde in Journal of the American College of Emergency Physicians Open. The study concluded that the 'double eights mask brace' "does not create an N95 equivalent in terms of filtration" but "would offer improved protection from airborne viruses when worn with a basic surgical mask."

Which is better?

In terms of being effective at blocking aerosols, there's far more evidence in favor of mask braces. That doesn't mean double-masking doesn't work, but the approach needs more studies to support the claim it helps fit and filtration.

There are other factors to consider besides effectiveness, however. Using two masks is wasteful, for example, while wrapping rubber bands round your head is like fixing a device that's inherently broken instead of replacing it with one that functions — in this case, a mask that fits properly in the first place.

Another factor is compliance. Some people refuse to cover their face — if you can't get those folks to comply with basic guidance to wear one mask, good luck getting them to wear two. Even with the emergence of new Covid variants, it may be tough to convince people to take action: in a poll of 1984 Americans, while 61% support double-masking, only 40% do it, despite thinking it's a good idea.

Telling the general public they need better masks might alienate some people to the extent that don't bother wearing anything, which is worse for public health.

As epidemiologist Saskia Popescu says, "Focus on finding one quality mask that meets the mark, versus trying to layer masks and create discomfort, difficulty breathing... or frustration that might lead to no mask at all."