Across the Atlantic, a team of researchers reminds us that the effectiveness of the mask lies in its filtration capacity. However, when it is not replaced in time, this capacity decreases too much, at the same time increasing the risk of contamination.
Today, there is no doubt that wearing a mask reduces the risk of contamination from the SARS-CoV-2 coronavirus. Nevertheless, it is necessary to change it after a few hours of use. According to a study published in the journal Physics of Fluids on December 15, 2020, wearing a used mask carries a greater risk of contamination than wearing nothing at all. Researchers from the University of Massachusetts at Lowell (USA) explain that the effectiveness of the mask depends mainly on its filtration capacity.
According to the scientists of the study, it is necessary that a mask has a filtration level of at least 65% to remain effective. On the other hand, in the case of a used mask, this same level of filtration can drop to 25%! There is therefore a very significant risk here of depositing ambient aerosols. Thus, the risk of contamination becomes much higher.
As part of their work, the researchers performed a model (see below) of the effect of a surgical mask on airflow inhaled by people who wear it. To do this, they identified the deposit of the droplets on the fabric as well as the face of the participants. According to the results, a mask that does not completely block the droplets spreads the latter over the entire surface of the face . In addition, the air flow is slowed down, favoring the inhalation of particles and therefore of the virus in the respiratory system. Let us remember in passing the fact that originally, the different masks did not all have the same effectiveness . The most efficient is obviously the FFP2 (or N95), followed by the surgical mask and then the fabric one. Moreover, the effectiveness of the latter is very relative.
In any case, changing them very regularly makes it possible to maintain a sufficient level of protection . Speaking of which, a Scottish company recently created a labeling system for face masks. By changing color over the hours, it informs the person when it is time to change the mask. Finally, regardless of the type of mask you wear, barrier measures are always essential. This includes hand hygiene as well as social distancing.
