While common mask materials block most droplets that spread the virus, a close range may not be enough.
Just wearing a mask may not be enough to prevent spread COVID-19 without taking social distance.
In Physics of Fluids, by AIP Publishing, researchers tested how five different types of mask materials affected the spread of droplets carrying the coronavirus when we cough or sneeze.
Each material tested drastically reduced the number of droplets dispersed. But at distances of less than six feet, enough droplets to potentially cause disease still reached different materials.
“A mask certainly helps, but if people are very close to each other, there is still a chance of spreading or contracting the virus,” said Krishna Kota, associate professor at New Mexico State University and one of the authors. of the article. “It’s not just masks that help. It is both the masks and the distance. “
The device used by researchers to study how masks block simulated respiratory droplets containing the COVID-19 virus. Credit: Javed Akhtar
At the university, researchers built a machine that uses an air generator to mimic people’s coughs and sneezes. The generator was used to blow tiny liquid particles, such as the airborne droplets sneezing and coughing, through laser plates into an airtight square tube with a camera.
They blocked the flow of the droplets in the tube with five different types of mask materials: a plain cloth mask, a two-layer cloth mask, a wet two-layer cloth mask, a surgical mask, and a medical-grade N-95 mask.
Each of the masks captured the vast majority of the droplets, ranging from the plain cloth mask, which lets about 3.6% of the droplets through, to the N-95 mask, which statistically retains 100% of the droplets. But at distances of less than six feet, even those small percentages of drops can be enough to make someone sick, especially if someone with COVID-19 sneezes or coughs multiple times.
A single sneeze can contain up to 200 million tiny virus particles, depending on how sick the carrier is. Even if a mask blocks a huge percentage of those particles, enough can escape to make someone sick if that person is close to the wearer.
“Without a face mask, it is almost certain that many strange droplets will be transferred to the sensitive person,” said Kota. “Wearing a mask provides substantial, but not complete protection to a susceptible person by reducing the number of strange sneezing and coughing droplets in the air that would otherwise enter the person without the mask. Attention should be paid to minimizing or avoiding direct face-to-face or frontal human interactions, if possible. “
The study also did not take into account leakage from masks, whether worn properly or improperly, which may contribute to the number of droplets that end up in the air.
Reference: “Can face masks provide protection against sneezes and cough drops in the air in close-up, face-to-face human interactions? A Quantitative Study ”by Krishna Kota, Javed Akhtar, Abner Luna Garcia, Leonardo Saenz, Sarada Kuravi and Fangjun Shu, December 22, 2020, Physics of liquids.
DOI: 10.1063 / 5.0035072