Should we wear two masks rather than one? The question arises after the publication of a study of American Centers for Disease Prevention and Control (CDC) on February 10, 2021, which claims that wearing two masks on top of each other provides enhanced protection against covid.

A loose mask is less effective

The objective of masks is on the one hand to reduce the expiration of droplets by infected people and on the other hand to reduce the exposure of non-contaminated people. An objective to be reinforced since the arrival of the new variants of the coronavirus, which are more contagious.

But the less the masks are modeled on the face, the less effective they are, because they let air escape to the sides, remind the CDC. Fabric masks or surgical masks, which are looser, are therefore less effective than FFP2 (or KN95).

To read also: Masks: what are the new recommendations of the High Council of Public Health?

92.5% protection with two masks

In January 2021, the CDC therefore carried out laboratory simulations on the reduction of air leaks with different models, including a fabric mask superimposed on a surgical mask and a surgical mask with elastic bands tied near the edges themselves folded towards inside.

While the non-tied surgical mask and the cloth mask block only 42% and 44.3% respectively of the aerosols dispersed by a cough, the combination of the two rises to 92.5% protection. Because the fabric mask comes to press the surgical mask on the face.

Mask tied or adjusted

In another experiment, exposure to an unmasked infected person was reduced by 83% with a double mask and by 64.5% with a mask tied to the face or if a plastic “mask adjuster” was worn over a face mask. surgical mask.

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This means these masks work and work best when fitted and worn correctly.“, said Rochelle Walensky, director of the CDC, during a press briefing.

In contrast, US health authorities do not recommend wearing two surgical masks or two FFP2 masks. Because unlike the fabric mask, the second surgical mask or FFP2 will not press the first mask to the face and will not make it less loose.

Based on these experiences, the CDC has since updated their information to the public on masks with these new options.

Recommendations posted on the CDC website on February 10, 2021.

A greater risk of contamination?

But in France, such recommendations are not on the agenda. “Wearing two masks layer upon layer can improve filtration if the fabrics are different“, tissue and surgical for example, recognizes the French standardization association (Afnor). “On the other hand, it will certainly pose a problem of breathability, making it difficult to support the mask “ when talking or walking, notes the Afnor.

Another limit, more problematic: wearing two masks increases the risk of contamination, according to Afnor. Because if they are less comfortable, they will have to be adjusted or removed and therefore touched, having necessarily washed their hands. In France, the rule therefore remains unchanged: wear a well-fitting mask, blocked on the nose and which goes down to under the chin.