Is it advisable to use a double mask to protect against covid-19?

The Centers for Disease Control and Prevention (CDC) on Wednesday recommended improving the fit of masks so that they filter better and further reduce the risk of contagion. To do this, they suggest systems such as using knots or even a fabric mask over the surgical one. The alternative is to use a single high protection mask, type N95, but the goal is the same: to ensure that there are no side slits. This recommendation from the CDC is an interesting measure when it comes to improving the capacities of certain masks which do not have the levels of protection required by certain risky situations.

After the initial uncertainty at the start of the pandemic and the absence of masks on the market, the recommendation was to avoid contagion by maintaining a cautious safety distance to avoid transmission. A few weeks later, the need to wear masks to prevent transmission in high-risk areas was confirmed. Insofar as the regulations imposed the obligation to wear a mask in all public places, the use of a mask became widespread. This has also been possible because they have become more accessible.

SARS-CoV-2 is a virus transmitted by the respiratory route. This evidence, however, involves a debate on the vehicle by which the virus enters our body, the droplets of saliva or the aerosols. The particles that we emit when we speak, cough, and even breathe are the vehicles the virus uses to spread from person to person. The size of these particles and the amount of virus they contain are two determining factors for infection.

Faced with the different risk situations in which a mask must be used, it is also necessary to take into account the variety of masks available and their level of protection. The main types of masks used by the population are of four types: fabric, hygienic, surgical and high protection or FFP2 (in some places N95, with equivalent effectiveness).

Sheet masks can have a wide variety of properties, depending on the characteristics of the materials used in their manufacture, but in many cases they are not approved in terms of filtration level. It is possible that some retain the virus very effectively, and even some made with materials containing compounds with silver or copper may have viricidal properties.

Limited effectiveness

In the case of hygienic masks, their effectiveness is limited and their use is not recommended to avoid transmission of the virus.

Surgical masks have features which, due to their ease of use and level of containment, have become the most popular masks. Its structure contains in most cases three layers, the exterior of which has hydrophobic properties and the interior, which is in contact with our skin, mouth and nose, the ability to absorb moisture.

These masks can have pore sizes between 2 and 10 microns and can contain about 80% of the particles that may remain in the air. In addition to the size of its pores, the material’s electrical charge helps attract airborne particles along with the microorganisms.

Finally, FFP2 approved masks have the ability to filter over 92% of particles in the air. These, in addition to the properties mentioned for surgical purposes, contain at least six layers of insulation and the pore size of the mesh thereof is less than 0.5 micron.

To all the characteristics previously exposed, we must add the fact that the daily and continuous use of masks is associated with their deterioration and accumulation of material in the pores of the fabric, the difficulty of breathing with them after a few hours and the loss of its effectiveness.

Beware of the accumulation of microorganisms

In addition to these characteristics, its continued reuse can lead to the accumulation of microorganisms and the risk that such an accumulation causes on the skin and respiratory system of some people, therefore its replacement is recommended.

In this context, and with the idea of ​​increasing its protective capacity, the use of a double mask can be an interesting option in certain situations, but it must be qualified.

Not all people are at the same risk from the virus, and not all situations they face involve the same level of risk. Also, wearing multiple masks can make it harder for some people to breathe. The use of both might be recommended in high risk situations where, for example, an FFP2 mask is not available, or in personal situations where a person has difficulty ensuring that the mask closes perfectly. the possible spaces remaining free if this is not the case. properly adjusted.

In this sense, the recommendations concerning the situations in which the use of a double mask is suggested should be clarified. These should be those in which the use of FFP2 masks is recommended but there is no access.

* The author of this article is a virologist and professor of microbiology at the Faculty of Pharmacy, CEU San Pablo University

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