Even if ordinary mask materials block most of the drops that spread the virus, they may not be enough at close distances.
Simply wearing a mask is not enough to prevent the spread COVID-19 without social distancing.
Into the Fluid physics, published by AIP, the researchers tested how five different types of mask materials influenced the spread of the drops that carry the coronavirus when we cough or sneeze.
Each material tested dramatically reduced the number of drops that were scattered. But at distances of less than 6 feet, enough drops to potentially cause disease managed to reach through several materials.
“A mask certainly helps, but if people are very close to each other, there is still a chance that the virus will spread or contract,” said Krishna Kota, an associate professor at New Mexico State University and one of the authors of the article. “It’s not just the masks that will help. There are both masks and spacers. “
The device used by researchers to study how masks block simulated respiratory droplets carrying the COVID-19 virus. Credit: Javed Akhtar
At the university, researchers built a machine that uses an air generator to mimic human coughing and sneezing. The generator was used to throw small liquid particles, such as sneezing and coughing air droplets, through laser sheets into a sealed square tube with a chamber.
They blocked the flow of droplets from the tube with five different types of mask materials – a regular cloth mask, a two-layer cloth mask, a two-layer wet cloth mask, a surgical mask, and an N-95 medical grade mask. .
Each of the masks captured the vast majority of the drops, ranging from the usual cloth mask, which allowed about 3.6% of the drops to pass, to the N-95 mask, which statistically stopped 100% of the drops. But at distances less than 6 feet, even those small percentages of drops can be enough to make someone sick, especially if a person with COVID-19 sneezes or coughs several times.
A single sneeze can carry up to 200 million small virus particles, depending on how sick the carrier is. Even if a mask blocks a huge percentage of these particles, it could escape enough to make someone sick if that person is close to the wearer.
“Without a face mask, it is almost certain that many foreign drops will transfer to the susceptible person,” Kota said. “Wearing a mask will provide substantial, but not complete, protection to a person susceptible to a decrease in the number of foreign sneezes in the air and cough drops that would otherwise enter the person without a mask. Consideration should be given to reducing or avoiding close human face-to-face or frontal interactions, if possible. “
Also, the study did not take into account the leaks from the masks, whether they are worn correctly or improperly, which can add to the number of drops that make their way into the air.
Reference: “Can face masks provide protection against sneezing and cough drops in close, 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, Fluid physics.
DOI: 10.1063 / 5.0035072