In a new study, researchers found that simply wearing a mask may not be enough to prevent the spread of COVID-19 without social distancing.
They tested how five different types of mask materials impacted the spread of droplets that carry the coronavirus when people cough or sneeze.
Every material tested dramatically reduced the number of droplets that were spread.
But at distances of less than 6 feet, enough droplets to potentially cause illness still made it through several of the materials.
The findings showed that a mask definitely helps, but if the people are very close to each other, there is still a chance of spreading or contracting the virus.
The research was conducted by a team at New Mexico State University.
At the university, researchers built a machine that uses an air generator to mimic human coughs and sneezes.
The generator was used to blow tiny liquid particles, like the airborne droplets of sneezes and coughs, through laser sheets in 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 regular cloth mask, a two-layer cloth mask, a wet two-layer cloth mask, a surgical mask, and a medical-grade N-95 mask.
The team found each of the masks captured the vast majority of droplets, ranging from the regular cloth mask, which allowed about 3.6% of the droplets to go through, to the N-95 mask, which statistically stopped 100% of the droplets.
But at distances of less than 6 feet, even those small percentages of droplets can be enough to get someone sick, especially if a person with COVID-19 sneezes or coughs multiple times.
A single sneeze can carry 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 could escape getting someone sick if that person is close to the carrier.
The team says without a face mask, it is almost certain that many droplets will transfer to the susceptible person.
Wearing a mask will offer substantial, but not complete, protection to a susceptible person by decreasing the number of foreign airborne sneeze and cough droplets that would otherwise enter the person without the mask.
Consideration must be given to minimize or avoid close face-to-face or frontal human interactions, if possible.
The study also did not account for leakage from masks, whether worn properly or improperly, which can add to the number of droplets that make their way into the air.
One author of the study is Krishna Kota, an associate professor.
The study is published in the Physics of Fluids.
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