Cloth homemade masks are capable of keeping viruses from spreading well even while talking and coughing, a new study published in Extreme Mechanics Letters has shown. Their effectiveness is comparable to that of conventional medical masks. They can be an effective part of COVID-19 prevention combined with social distancing, scientists say.
Previously, some research has addressed the question of how cloth masks trap aerosol droplets containing viruses. Authors new research argue that when coughing, sneezing and talking, relatively large droplets are formed, which have been very little researched in the context of the current pandemic. Therefore, there was some gap in understanding the protective effectiveness of some tissues.
Aerosol is usually called a suspension of droplets with a diameter of less than 5 micrometers. But large droplets can also be a problem. There is a possibility that at high acceleration, they can break on the fabric of the mask and contribute to the formation of a viral aerosol in the air.
Scientists emphasize that masks should be made of breathable fabrics, since otherwise the exhaled air will not pass through the mask, but escape from the side. For the experiments, they chose 11 breathable fabrics that are in every home (they are used to make clothes, bedding, kitchen towels). Scientists have tested how well fabrics allow air to pass through.
Scientists tested the effectiveness of tissues in filtering droplets using a special aerosol generator. The role of a virus substitute in the experiment was played by nanoparticles of the appropriate size. Scientists counted the number of nanoparticles slipping through the masks.
It turned out that all tissues are good at retaining aerosol, blocking particles with a size of 100 nanometers. They were effective when scientists simulated coughing, sneezing, and talking in an experiment. Even when used in one layer, they retained a large number of particles.
“In two or three layers, even the lightest fabrics — such as those used to make T-shirts — block aerosols as effectively as a regular medical mask. At the same time, such a homemade mask may be more breathable. ” told study author Professor Taher Saif from the University of Illinois.