One popular style of face covering may not do much to limit the spread of the coronavirus, according to a study from Duke University.
The researchers found that although most of the cotton, cloth or surgical style tests tested were effective in reducing the amount of respiratory drops a person was expelled while talking, the ‘neck gland’ as a neck fleece actually resulted in more small drops that were expelled.
“We attribute this to the fleece, the textile, the breaking of those large particles into many small particles,” Martin Fischer, an associate research professor at Duke, said in a news release.
The new coronavirus that causes COVID-19 is most often spread from person to person through respiratory drops that drive us all out of our mouths when we talk heavily, sneeze, cough or breathe, according to most experts.
Fischer said it is possible that releasing more small drops through a thin mask is worse than issuing larger drops without any shield at all.
“[The smaller particles] tend to hang in the air longer, they can be removed more easily in the air, so this can actually be counterproductive to wearing such a mask, “said Fischer.” It is not the case that every mask is better is like nothing. There are some masks that actually hurt or do good. ‘
However, some have said that conclusion is too early and we do not have enough information to explain that these masks do more harm than good. News director Susan Matthews points out that researchers are only testing one subject with the gaiter-style mask, increasing the chances that the mask just does not fit, or that there was something different with the mask than the test subject.
The subject also repeated only the short phrase “stay healthy, people,” 10 times for each mask. The subject did not speak in different volume levels, coughing, sneezing or simulating other conditions such as heavy breathing during exercises. Gaiter masks are very popular with runners because of their light construction and looser fit.
A July University of Wisconsin-Madison study found that gaiters were more effective than other types of masks in catching drops from a simulated cough, but in that study “snug-fit” used homemade gaiters made of tightly woven fabric with a metal nose piece and elastic to ensure a good fit.
Matthews also notes that we do not know if a person who expels a higher number of small droplets is more likely to spread the disease than a person who produces fewer, larger flares of virus-laden bacon.
The Duke team’s findings were published online last week in Science Advances, a peer-reviewed journal.
Fisher and the team at Duke tested 14 different types of masks with cardboard, laser lights and a mobile camera, as you can see in the short video below.
The subject repeats the same syllable in contraption, first without mask, then with the different styles of masks to see which ones were most effective. The laser makes visible the drops coming out of a person’s mouth and the camera detects those drops to count.
The team found that surgical masks, such as cotton, cloth and polypropylene masks, were effective in dispersing the drops as the subject spoke in a normal voice. The best performing masks were the medical class N95 masks – without valves – used by medical professionals.
The neck fleece (mask # 11 in the photo above) actually resulted in more drops being counted. The bandana reduced the number of drops by about half, the others reduced the number of drops to 20 percent or less of the maskless count.
One of the investigators told The Washington Post that the gaiter that was poorly tested was made of a lightweight, polyester spandex material, marked as a breathable item for outdoor sports activities.
“If you can see through it if you put it on a light and you can easily blow it through, it’s probably not protecting anyone,” Warren S. Warren, a co-author of the newspaper, told the Post.
N95 medical masks with valves performed much like cotton masks, with the researchers noting that the valves were designed to keep drops from the mask from the outside, and not to stop the person wearing the mask from droplets expels who others could then inhale.
However, the general takeaway of the paper is clear. While some masks perform better than others, most masks are effective in reducing the drops that spread the coronavirus.
“Wearing a mask is a simple and easy way to reduce the spread of COVID-19,” said Dr. Eric Westman, a duke doctor who worked with Fischer to design the experiment, said in a news release. “About half of infections come from people who have no symptoms, and often do not know they are infected. They can spread the virus unconsciously like coughing, sneezing and just talking.
‘If everyone wore a mask, we could stop up to 99% of these drops before they reach anyone else. In the absence of a vaccine or antiviral drug, it is the only proven way to protect others than yourself. ”
This study was designed as a proof-of-concept of the researchers’ technique for measuring droplet spread. The researchers say further research is needed to test different masks under a variety of conditions, such as speaking at different volumes, such as coughing and numbness.
“We strongly encourage everyone to wear a mask, but we want to make sure that when you wear a mask and you make the effort to make a mask, you make or wear one that actually not only helps you, but everyone helps, “Fischer said.
