CDC: wearing a double mask could reduce infections by up to 96%

The fit of the mask is key to achieving its protective effect against COVID-19, either when we use a surgical mask or with FFP2 or FFP3. However, although the latter have a shape that facilitates their adaptation to the face, it is true that the surgical ones do not so much, since air can filter around their edges, especially through the lateral spaces. Now, a study by the US Centers for Disease Control and Prevention (CDC) has concluded that the use of a double mask, that is, wearing a cloth mask over a surgical one, could significantly reduce the number of infections. .

This is so because the cloth ones help the surgical fit better and prevent those air leaks. The tests carried out by the CDC combined the two types of face masks and it has been concluded that wearing a cloth face mask over a surgical one reduces exposure by up to 82.2% for a person who does not wear a mask to protect themselves.

In the cases in which two people interact using these double masks, the exposure to potentially infectious aerosols decreased by approximately up to 96.4%, so it would protect more or better from a possible spread of the SARS-CoV-2 coronavirus. According to CDC experiments, the use of surgical masks without knotting blocks 44.3% of particles and cloth masks alone, 44.3%.

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Knots or adjusters are also a good option

Wearing two masks can be uncomfortable to breathe or obstruct peripheral vision for some people. In these cases, the researchers recommend using elastic adjusters that sit at the back of the head and a tie at the base of the earmuffs to improve effectiveness. Thus, in another study they found that the addition of mask adjusters to two medical procedure masks improved their efficiency to similarly high levels.

The tests were carried out with a three-layer surgical mask and a three-layer cotton fabric mask and 10 combinations that included the use of both at the same time, only one or even with additional knots for a better fit. To see the leak that was produced, a person's cough was simulated with nozzles that emitted potassium chloride particles from 0.1 to 7 μm.

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The researchers have cautioned that the results may vary depending on the masks used, and that these findings should not be generalized, especially to children due to their smaller size or to men with beards and other facial hair that interfere with fit. They also note that tying and folding the mask to try to fit it better can change the shape of the mask so that it no longer completely covers both the nose and mouth of people with larger faces.