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Seeing means believing: What is the effectiveness of face masks?
Using simulating the flow of coughs and sneezes, researchers have evaluated the effect of face masks on preventing the spread of the virus.
Homemade face masks and non-medical fabrics provide at least the ability to stop for the smallest breathing droplets of the magnifying glass.
Currently, there are no specific guidelines on the most effective facial mask materials and designs to minimize the release of droplets from coughing or sneezing to reduce COVID-19 transmission. While previous studies have been conducted on how medical grade masks work, information about fabric coatings used by the vast majority of the general public is sparse.
Research by the University of Florida's School of Engineering and Computer Science, recently published in the Journal of Physics of Fluids, shows a method for evaluating the effectiveness of face masks in blocking droplets through the visualization of simulated coughs and sneezes. The reason for recommending the use of masks or other face coverings is to reduce the risk of cross infection by transferring respiratory droplets from infected people to healthy people.
The researchers used the visualization of the current in vitro using a sheet of laser light and a mixture of distilled water and glycerin to produce artificial fog that constitutes the content of a cough. They observed droplets out of the mannequin's mouth while simulating coughing and sneezing. They tested masks that are readily available to the public and are not very different from the medical masks used by the medical staff. They tested a single-layer mask, a homemade mask that was stitched using two layers of cotton dut fabric consisting of 70 yarns per inch, and a non-sterile cone-style mask available in most pharmacies. By placing these different masks on the mannequin, they were able to map the path of droplets and show their different performance.
The results showed that folding and household face masks partially stop the aerosol respiratory droplets. However, household masks equipped with several layers of nitted fabric and conical and medical style masks available in the revereds are the most effective in reducing the dispersion of droplets. These masks were able to significantly reduce the speed and amplitude of discharge, despite some leaks through mask materials and small gaps of edges.
Importantly, coughs without masks were able to move substantially farther than the 1.8-meter safety distance directive recommended at the moment. Without masks, droplets moved more than 2.4 meters. With a simple one-layer cloth mask they traveled 90 cm. They travelled 30 cm with a folded cotton napkin. With a cotton mask, they traversed 6 cm. And with a conical-style mask, the droplets moved about 20 cm.
Professor Siddhartha Verma (lead author and assistant professor who co-authored this article along with Manhar Dhanak, PhD, Head of Department, Professor and Director of SeaTech and John Frakenfeld, a technical expert, all of which are members of the FAU Department of Mechanical and Ocean Engineering), said: "In addition to providing early indications of the effectiveness of protective equipment, the images used in our study can help people reasonably think about social distancing guidelines and Have recommendations for using face masks."
"Promoting widespread awareness of effective preventive measures at this time is very important, as in many states, especially Florida, we are seeing a significant increase in cases of COVID-19 infection."
When the mannequins were not equipped with masks, they predicted droplets farther than the 1.8-meter distance guidelines currently recommended by the U.S. Centers for Disease Control and Prevention. The researchers observed drops that move roughly 50 seconds to 3 meters. In addition, tracker droplets were suspended in a quiet environment for up to three minutes in the air. These observations, in combination with other recent studies, suggest that current social distancing guidelines may need to be updated to take into account the transmission distance of aerosol-based pathogens.
"We found that although particulate matter moves up to 3 metres, the majority of the outer droplets have fallen to the ground at this point," Dhanak said. "More importantly, the number and concentration of droplets decreases with increasing distance, which is the main reason for social distancing."
The pathogen responsible for COVID-19 is found primarily in respiratory droplets that are excreted when coughing, sneezing or even speaking and breathing by infected people. Apart from COVID-19, respiratory droplets are also the main means of transmission of other viral and bacterial diseases such as colds, influenza, tuberculosis, SARS (severe acute respiratory syndrome) and MERS (Middle East respiratory syndrome). These pathogens are in the respiratory droplets, which may sit on healthy people, lead to direct transmission, or sit on insanity objects and spread in case of close contact with the person.
"Researchers have shown how masks can significantly reduce the speed and amplitude of respiratory droplets and secretions. In addition, they have discovered how simulated coughs can move substantially farther than the 1.8-meter distance directive recommended now," said Stella Batalama, Dean of the FAU School of Engineering and Computer Science. "Their research demonstrates the method of conducting simple visual tests using materials that are readily available, which may help healthcare professionals, medical researchers and manufacturers evaluate the effectiveness of face masks and other personal protective equipment."