Florida Atlantic University researchers experimented with different materials and styles of non-medical masks and found that a well-made stitched mask with two layers of quilted fabric was the most effective in stopping the spread of droplets from cough and emulated sneezing.
The researchers said they chose to test these face coating styles because they are readily available to the public and do not stray from providing medical-grade masks and respirators for healthcare professionals.
“While there are some previous studies on the effectiveness of medical-grade equipment, we do not currently have much information about the fabric-based coatings that are more accessible to us,”
“Our hope is that the visualizations presented in the document will help communicate the rationale behind the recommendations for social distancing and the use of face masks.”
The study published Tuesday in the journal Physics of Fluids.
Emulation of coughing and sneezing
In the experiment, a manikin’s head was padded inside to emulate a person’s nasal passages and mounted at a height of 5 ‘8 “to approximate the height of an adult male. The researchers” freed ” sneezing or coughing using a hand pump and a smoke generator.
They then used a laser to detect the droplets as they were coughed and sneezed from the mannequin’s head, mapping the droplet paths and examining how different designs and materials alter that path.
The main challenge for researchers was how to faithfully simulate a cough and sneeze.
“The setting we used (is) a simplified cough, which is actually complex and dynamic,” said Verma in a note.
They found that the droplets of a simulated uncovered cough were able to travel more than 8 feet; with a bandana they walked 3 feet, with a folded cotton handkerchief, they walked 1 foot, 3 inches; and with the cone mask, the droplets traveled about 8 inches. With the sewn quilted mask, they traveled 2.5 inches.
“We found that although unobstructed turbulent jets were observed traveling up to 12 feet, most of the expelled droplets fell to the ground at this point,” said Manhar Dhanak, a professor in Florida’s Department of Ocean and Mechanical Engineering Atlantic University and coauthor of the study.
“It is important to emphasize that both the number and concentration of the droplets will decrease with increasing distance, which is the fundamental logic behind social distancing.”
Higher thread counting alone was not more effective, the researchers said. In their experiment, the bandana had the highest count and was the least effective.
They claimed that their experiment could help healthcare professionals, medical researchers and manufacturers assess the effectiveness of facial masks.