With a folded handkerchief mask over the nose and mouth, droplets from coughs and sneezes traveled 1 foot, 3 inches. Photo courtesy of Florida Atlantic University College of Engineering and Computer Science
June 30 (UPI) -- To figure what types of homemade mask best prevent the spread of COVID-19, scientists at Florida Atlantic University used glycerine and laser light to illuminate the movement of droplets from coughs and sneezes.
Researchers report the distance droplets move can be cut by more than half by using a homemade mask -- from more than 8 feet, to less than 2 feet.
For the new study, published Tuesday in the journal Physics of Fluids, researchers focused on cloth-based coverings, as most other research has focused on medical-grade masks.
"Such masks have been recommended for public use by various agencies, but there are no clear guidelines on the best material or construction technique that should be used," Siddhartha Verma, lead author and an assistant professor at Florida Atlantic, told UPI in an email.
They found that without a mask, droplets traveled more than 8 feet -- beyond the 6 feet recommended for "social distancing." With a bandana, droplets traveled 3 feet, 7 inches. With a folded cotton handkerchief, the droplets traveled 1 foot, 3 inches. The stitched quilted cotton mask proved most effective, allowing droplets from the nose and mouth to travel just 2.5 inches.
Scientists also tested a cone mask, widely available at local pharmacies. The commercial mask allowed droplets from simulated coughs and sneezes to travel 8 inches.
For the study, researchers sprayed a solution of distilled water and glycerin through the mouth of a mannequin to create glow-in-the-dark droplet clouds resembling those produced by coughs and sneezes.
Researchers projected the glow-in-the-dark coughs and sneezes through several types of homemade masks, using cameras to measure how far the droplets traveled.
"We visualized the droplets in a sheet of laser light," said co-author Manhar Dhanak, department chair, professor and director of SeaTech at Florida Atlantic. "The droplets scatter the light and hence become visible."Researchers determined that creating a tight seal and layering material were the most important factors in creating an effective barrier.
"The effectiveness of a mask does not necessarily depend on the thread-count of the fabric," Verma said.
While masks are effective in reducing the risk of transmission of viral infections, Dhanak said that "given the possibility of leakage, it is important to use a combination of social distancing, mask use, hand-washing and other recommendations from healthcare professionals in order to minimize the chances of transmission."
In future studies, Verma and Dhanak plan to more closely examine leakage around the sides of different kinds of masks and how to curtail it."We are also looking into the impact of environmental conditions in a room on the spread of the droplets and wider applications of our techniques in design of barriers, shielding and air-conditioning systems in the workplace and open-plan offices," Verma said.