In a recently published study, researchers discovered a simple method to evaluate the effectiveness of different types of masks, analyzing more than a dozen different face masks, ranging from hospital-grade N95 respirators to bandages. Of the 14 masks and other masks tested, the study found that some easily accessible cotton fabric masks are nearly as effective as standard surgical masks, while popular alternatives such as neck stones may be worse. than not wearing a mask at all.
“You can really see that the mask is doing something,”; said one of the study’s co-authors, Warren S. Warren, a professor of physics, chemistry, radiology and biomedical engineering at Duke. “There’s a lot of controversy and people say, ‘Well, masks do nothing.’ “Well, the answer is some no, but most do.”
The search for a way to determine the effectiveness of various masks began with a request from a professor at Duke Medical School, who was working to provide at-risk and undeserved populations in Durham, NC, with critical face masks, according to an announcement from the university. In the face of so many types of masks that all claim to have the ability to block the virus, the professor asked for help – in the physics department at the university.
Enter Martin Fischer, a chemist and physicist.
Using a simple contraceptive that utilizes the power of a laser, which can be easily purchased online for less than $ 200, and a cell phone camera, Fischer created a device that allowed his team to track individual particles of released from a person’s mouth when speaking. The rest of the configuration includes a box that can be made from cardboard and a lens.
“Summer is very simple, it doesn’t take a lot of resources,” Fischer said in a video produced by Duke. “Every research lab has these things flowing.”
Testing face masks was just as uncomplicated, according to the study published Friday in Science Advances, a peer-reviewed journal.
The speakers said the same phrase in the box without the mask and then repeated the process while wearing one. Coveringdo face mask was tested 10 times. Inside the device, airborne particles passed through a sheet of light created by the laser that hit the lens and produced visible bubbles that were recorded by the phone camera.
“Even very small particles can do this kind of thing [light] dispersing, “Warren said.” We were able to use dispersion, and then trace individual particles from frame to frame in the film, to actually count the number of particles that were emitted. “
A fitted N95 mask, which is most commonly used by hospital staff, was most effective, Warren said, noting that the mask allowed “dots at all” to escape. Meanwhile, a breathable guitar around the neck, much liked by runners for its lightweight fabric, ranked worse than the maskless control group.
“These neck ties are extremely common in many countries because they are very comfortable to wear,” Warren said. “But the exact reason why they are so convenient, which is that they do not restrict air, is why they are not doing a lot of work helping people.”
The high number of droplets can bind to the fabric of the neck vessels by breaking larger particles into smaller ones that are more likely to hang in the air longer, Fischer said in the video. This effect makes their clothing possibly “counterproductive”, he added.
“It’s not the case that every mask is better than nothing,” he said. “There are some masks that actually do more harm than good.”
Other types of face masks that can fall into that category are bandanas and knitted masks, the study found. An N95 mask with an exhalation valve also failed to be measured.
“These relief valves are fantastic if what you want to do is protect yourself from the outside world because air does not enter through them,” Warren said. “If what you are trying to do in this pandemic is to protect the outside world from you, it completely defeats the purpose.”
However, he stressed that people without access to medical class masks should not worry.
“We are not like a society where everyone will wear disposable N95 face masks,” he said. “It is not affordable and it is not reasonable.” The researchers specifically noted the effectiveness of conventional cotton masks, revealing that some of the ones tested performed as well as surgical masks, which come in second place in the N95. Experts with the World Health Organization have recommended that clothing masks should have three layers.
Although the study was not “a clinical trial” involving testing of “10,000 patients and seven different languages and all possible conditions,” Warren said his overall conclusions still stand.
“We are very careful not to pretend here,” he said. “We’re not going to try to say our evidence is that this is the yarn count you should use on the sheet for the two – foil cotton mask you’re doing.
“But the big picture of the house – that the masks work in reducing transmission and that some masks that you can easily get are better than others – potentially worth protecting everyone and getting us out. from this terrible situation, “he added.
Warren said he and his other researchers are now focused on producing a step-by-step guide to setting up the testing device. The team has already been approached by people from foreign countries, including Africa, who have expressed interest, he said.
“It is quite possible that people with a little scientific training can use this safely and quite effectively,” Warren said, noting that he does not recommend that the average person go out and try to build the device themselves. “The idea is that you can have community centers, groups that are helping to try different models. Especially since we are trying to offer face masks to a large number of people who do not have them, you want to make sure they work. “