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WASHINGTON, November 24, 2020 – The use of face masks to help slow the spread of COVID-19 has been widely recommended by healthcare professionals. This sparked studies exploring the physics of face mask use and disease transmission, as well as investigations into materials, design, and other issues affecting how face masks work.
In Fluid physics, by AIP Publishing, investigators looked at the research on face masks and their use and summarized what we know, so far, about how face masks filter or block the virus. They also summarize the design issues that still need to be addressed.
A key aspect of the function of the face mask is the size of the liquid droplets expelled from the nose and mouth when a person speaks, sings, sneezes, coughs, or even just breathes. Larger droplets, with sizes around 5-10 microns, are the most common. These droplets are however still quite small. For comparison, a human hair is about 70 microns in diameter.
Even smaller droplets, those smaller than 5 microns, are perhaps more dangerous. These can become aerosolized and remain suspended in the air for long periods of time. Of the many types of masks used (cloth masks, surgical masks, and N95 masks), only N95 can filter aerosol-sized droplets.
The performance of face masks worn for many hours, for example by healthcare or other essential workers, impacts the effectiveness of the overall wearing of the mask. Thermal comfort is an important issue, especially in hot and humid environments.
Investigators found that face masks made from hybrid polymer materials could filter out particles at high efficiency while simultaneously cooling the face. The fibers used in these special masks are transparent to infrared radiation, allowing heat to escape under the mask.
“There may be a relationship between respiratory resistance and face mask flow resistance that will need to be investigated for a face mask wear interval,” said author Heow Pueh Lee. “In addition, the environmental conditions in the compartmental space of the facemask will need to be quantified more precisely using miniaturized sensors and the development of human replicas for such studies.
Investigators also reviewed epidemiological studies aimed at finding out whether face masks reduce the effective number of reproductions. If the reproduction number drops below 1, the epidemic stops spreading. One study used COVID-19 data from New York State.
“The results suggest that the systematic use of effective masks, such as surgical masks, could lead to the eradication of the pandemic if at least 70% of residents use these masks in public consistently,” the author said. Sanjay Kumar. “Even less effective sheet masks could also slow the spread if worn regularly.”
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The article, “The Perspective of Respiratory Droplet and Aerosol Fluid Flow Behavior Through Face Masks in the Context of SARS-CoV-2,” is written by Sanjay Kumar and Heow Pueh Lee. The article will appear in Fluid physics on November 24, 2020 (DOI: 10.1063 / 5.0029767). After this date, it is accessible on https: /
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