Covid-19: Study evaluates filtration of different types of masks |See Health

2022-07-16 00:51:37 By : Ms. Dora Zhao

The transmission of the coronavirus is mainly through the inhalation of droplets of saliva and respiratory secretions suspended in the air.That's why wearing masks and maintaining physical distance are the most effective ways to prevent Covid-19, while there is no vaccine for everyone.Inexpensive, reusable and available in different colors and prints, fabric masks are among the most used by Brazilians.However, its ability to filter aerosol particles with a size equivalent to that of Sars-CoV-2 can vary between 15% and 70%, as revealed by a study conducted at the Institute of Physics of the University of São Paulo (IF-USP).Coordinated by Professor Paulo Artaxo and supported by Fapesp, the work is part of the initiative (Breathe!. The results were published in the Aerosol Science and Technology magazine. “We evaluated the filtration of 227 models sold in Brazil, either in pharmacies or popular retail stores. Our objective was to find out to what extent the population is really protected with these different masks”, Artaxo tells Agência Fapesp.To do the test, the scientists used equipment that produces, from a solution of sodium chloride, aerosol particles of controlled size – in this case 100 nanometers (SARS-CoV-2 is approximately 120 nanometers).After the aerosol jet was released into the air, the particle concentration was measured before and after the mask.The models that proved most effective in the test, as expected, were surgical masks and the PFF2/N95 type – both for professional use and certified.They filtered out between 90% and 98% of aerosol particles.Next are the TNT ones (made of polypropylene, a type of plastic) sold in pharmacies, whose efficiency ranged from 80% to 90%.Finally came the fabric ones – a group that includes models made with cotton and synthetic materials, such as lycra and microfiber.In this case, the filtration efficiency ranged between 15% and 70%, with an average of 40%.And some factors proved to be critical to increase or decrease the degree of protection.“In general, masks with a seam in the middle protect less, because the machine makes holes in the fabric that increase the passage of air.The presence of a nose clip, which helps to fix the mask on the face, considerably increases filtration, due to the better fit on the face”, comments Fernando Morais, doctoral student at IF-USP and the Institute of Energy and Nuclear Research (Ipen), who is the first author of the article.“But in all cases, efficiency decreases with washing, because the material wears out”, he concludes.According to Artaxo, the two-layer cotton masks filtered out considerably more aerosol particles than those made with just one.But from the third layer onwards, efficiency increased little, while breathability decreased considerably.“One of the novelties of the study was to evaluate the breathability of the masks, that is, the resistance of the material to the passage of air.TNT and cotton were the best in this regard.The PFF2/N95 type were not so comfortable.But the worst was one made with paper.This is an important aspect, because if the person can't stand even five minutes with the mask on, it's no use,” says Artaxo.As the authors point out in the article, although with varying efficiency, all masks help reduce the spread of the coronavirus and their use – associated with physical distancing – is fundamental in controlling the pandemic.They also state that the ideal would be the mass production of PFF2/N95 type masks to distribute free to the population - something that "should be considered in future pandemics", in the assessment of Vanderley John, coordinator of the initiative (breathe! and co-author of the study.“Today it is already proven that the main form of contamination is through the air.Wearing masks all the time is one of the best prevention strategies, so keep windows and doors open to ventilate the environments as much as possible”, recommends Artaxo.*This content is from Agência Fapesp.From BRL 9.90/monthFrom BRL 9.90/monthFrom BRL 9.90/monthFrom BRL 9.90/monthFrom BRL 9.90/monthFrom BRL 9.90/monthCopyright © Abril Mídia S A. 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