Infectious Disease

In line with the CDC, double masking presents extra safety

February 10, 2021

2 min read

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The authors do not report any relevant financial information.

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CDC researchers tested two modifications that they said would “significantly” improve the effectiveness of surgical masks as protection against SARS-CoV-2, including double masking – wearing a cloth mask over a surgical mask.

The other modification was to knot the ear loops of a surgical mask near the edges of the mask and insert the additional material (see Panel C here).

CDC mask infographic

Tests show that double masking, or knotting and tucking away medical masks, significantly improved fit and filtration, and decreased exposure of the wearer and those around the wearer.
Image credit: CDC

“Controlling SARS-CoV-2 transmission is important not only to reduce the widespread impact of the COVID-19 pandemic on human health and the economy, but also to slow virus development and develop variants, that could alter the dynamics of transmission or affect the usefulness of diagnostics, therapeutics and vaccines ” John T. Brooks, MD, A medical epidemiologist on the CDC’s COVID-19 emergency team and colleagues wrote.

“The data in this report underscores the finding that a good fit can increase the overall effectiveness of the mask,” they write. “Several simple ways to improve fit have been shown to be effective. Continued innovative efforts to improve the fit of fabric and medical procedural masks to improve their performance deserve attention. “

Brooks and colleagues conducted various experiments in January to evaluate the two methods. In the first experiment, they used a pliable elastomeric head shape to simulate a cough to test the effectiveness of different mask combinations in reducing the amount of particles emitted during a cough (source control). The second experiment assessed how effective the two modifications to medical procedural masks – surgical masks, for example – were in reducing exposure to aerosols during breathing.

The results of the first experiment showed that the untied medical procedure mask blocked 42% of the particles from a simulated cough alone, while the cloth mask blocked 44.3%. They found that combining the masks blocked 92.5% of the cough particles.

The results of the second experiment showed that adding a cloth mask over the medical procedure mask or knotting and tucking the medical procedure mask reduced exposure of an unmasked recipient by 82.2% and 62.9%, respectively.

Brooks and colleagues said that when the source was exposed and the recipient was fitted with the double mask or the tied and hidden medical mask, exposure of the recipient was reduced by 83% and 64.5%, respectively, and when the source and recipient were both were double masked or using knotted and hidden masks the exposure of the recipient was reduced by 96.4% and 95.9%, respectively.

Both modifications had drawbacks, the researchers found, including that “a double mask could interfere with breathing or impede peripheral vision for some wearers, and knotting and tucking away can change the shape of the mask so that it is both nostrils and not more completely covered mouths of those with larger faces. “

“We also recommend that masks have two or more layers, completely cover the nose and mouth, and fit snugly around the nose and sides of the face,” said CDC Director Rochelle P. Walensky, MD, MPH, said during a press conference at the White House.

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