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Increasingly, scientific research points to the effectiveness of masks as a method of brake of the new coronavirus . However, there are less studies on how to degrade with use, despite the fact that a lot of people reused in several occasions, even above and beyond their useful life. Therefore, a team of the University of Nicosia (Cyprus) has just been published in “Physics of Fluids” conclusions somewhat alarming: even with a mask, the drops of saliva could travel more than a meter away.
Talib Dbouk and Dimitris Drikakis , the authors of the research, and experts in fluid physics, used mathematical models to create potential flow paths of these droplets when a person coughs repeatedly, with and without mask . The results show that this tool of containment, you can reduce to the half the transmission of particles in the air, because without them, the drops can reach up to five meters away. However, the filtration efficiency of the masks is seriously affected by the coughing, a symptom very common in the Covid-19 .
Even with a mask, there is a danger
The results are alarming. In computer simulations one can observe how the use of the mask is effective especially at the beginning of an attack cough: on the first boot, the fabric is able to contain up to 91% of the transport of saliva . However, according to increases in the time, every time more drops will escape from the mask , “traveling even more than 1.2 meters of distance”, say researchers, who for the simulation included environmental conditions of wind speed of zero, an ambient temperature of 20 degrees C, pressure of 1 atmosphere and a relative humidity of 50%; also included the temperature of the mouth at 34 degrees C and the skin of the face is 32 degrees C.
Evolution of the cough by a few seconds, with mask and without mask – Talib Dbouk and Dimitris Drikakis
But the simulations were not limited only to the first five seconds. In a video prepared by the researchers (and that is in the header of this news) it can be seen how the drops get beyond the 1.6 metres distance a attack of cough prolonged of 17 seconds , reaffirming the idea that, while the fabric protects fairly of the spread of the virus, is not enough in short distances and loses its effectiveness as it is used.
big Drops against droplets
The researchers also point out that a few drops escape through the sides of the mask and the size of the droplets, which varies according to the intensity of the cough, also influences the flow of drops, while “ it is not yet clear if the drops are big or small, are the most infectious” , aiming for his part, Dbouk. For this reason, the researchers warn that the use of mask “does not provide complete protection” , so the social distancing “remains essential”.
In fact, the researchers recommend for the health and the workers who are in direct contact with the virus, “a team of personal protection, much more comprehensive, including helmets with air filters built-in, face shields, gowns and disposable gloves and double.”
on the other hand, the researchers also urge manufacturers and regulatory authorities to consider new criteria to evaluate the performance of the mask that take into account the physics of the flow and the dynamics of the cough, as well as new studies on how the masks are degraded with the use of the time.