- New research shows that the most effective homemade face masks are those made with tightly woven fabric and providing a good seal along the edges.
- Bandanas were not found to be effective.
- N95 masks need to be properly fitted and should be reserved for those who need them.
- Surgical face masks are another effective option in areas where they’re readily available.
A team of researchers claims to have found the best materials for homemade face masks, writes Maria Cohut for Medical News Today.
The material is a combination of either cotton and chiffon or cotton and natural silk, both of which appear to effectively filter droplets and aerosols.
Their findings, featured in the journal ACS Nano, suggest that certain fabric combinations may go some way toward halting the spread of the new coronavirus.
Face masks to control the pandemic
Since the start of the COVID-19 pandemic, health agencies in the United States have recommended face mask usage to limit the spread of the novel coronavirus.
Since there isn’t enough medical-grade personal protective equipment to go around, many Americans have sewn their own fabric masks or simply used a bandana.
While it’s understood that some level of protection is better than none, there hasn’t been much information on the effectiveness of these homemade masks.
A new study, published today in the scientific journal Physics of Fluids from AIP Publishing, sheds new light on how the materials and construction of a face mask can impact its effectiveness.
“All of the major health agencies have now issued recommendations for the general public to use some sort of face covering, but there are no clear guidelines on the types of material or designs that should be used,” explained Siddhartha Verma, PhD, the study’s lead author who also serves as assistant professor in the department of ocean and mechanical engineering at Florida Atlantic University’s College of Engineering and Computer Science.
“While there are a few prior studies on the effectiveness of medical-grade equipment, we don’t have a lot of information about the cloth-based coverings that are most accessible to us at present, given the need to reserve medical-grade supplies for healthcare workers,” Verma told Healthline.
Mask usage 101
Dr. Teresa Amato, director of geriatric emergency medicine at Northwell Health, told Healthline that even as experts scramble to understand a pandemic that was virtually unheard of 6 months ago, mask wearing is a no-brainer in terms of decreasing transmission.
“It’s especially true with the more people you have wearing a mask,” she explained. “If you are infected and you wear a mask, you will decrease the likelihood of transmission. You’re wearing it to protect the people around you and you’re also wearing it to protect yourself from getting it. It’s really important to emphasize that more people wearing masks will decrease transmission overall.”
When it comes to specific masks, they can range from a simple folded bandana to hand-sewn cloth masks to N95 respirator masks.
While N95 masks provide a high level of protection, they aren’t a realistic option for most people, as they should be earmarked for frontline workers.
Amato also points out that they aren’t exactly a one-size-fits-all option. “N95 masks need to be fitted, and the wearer needs to be fit-tested to make sure that it’s on there appropriately,” she said.
“Otherwise, wearing one is actually not very useful. So we’re not talking about the N95, we’re talking about either surgical masks or cloth masks.”
Verma and his team sought to find out which non-N95 masks would be most effective. He said that the simplest masks — either a bandana or handkerchief — were virtually ineffective.
“I was a bit surprised to see how much leakage could occur through the bandanas and folded handkerchief masks we tested, even through multiple folds of the cotton fabric,” he said.
Ultimately, Verma and his colleagues determined that the most effective homemade masks were those that were well-fitted with multiple layers of quilting fabric.
Cone-style masks worked well
“Quilting cotton, with two layers stitched together, turned out to be the best in terms of stopping capability,” said Verma.
“For minimizing the chances of transmission, it is important to use masks made of good quality tightly woven fabric, as well as mask designs that provide a good seal along the edges without being uncomfortable.”
Amato says another useful mask option, for those who can obtain them, are simple surgical masks.
“In the beginning, we were kind of holding onto those for healthcare workers, but now we have a good supply of them,” she said. “They’re probably the most comfortable to wear. They’re very lightweight and they afford good protection.”
How well the mask fits is also crucial
In their study, the team experimented with various samples of cotton, chiffon, flannel, silk, spandex, satin, and polyester — on their own and in combination.
They tested the fabric to see if it could filter out tiny aerosol particles. This is because researchers believe that SARS-CoV-2 may disseminate not just through droplets — for instance, from coughs — but also through minute particles that spread when people simply breathe, which are much harder to catch.
The team fanned particles measuring 10 nanometers to 6 micrometers in diameter over the various fabric samples at an airflow rate similar to that of a person’s breath when they are at rest.
The researchers found that a sheet of tightly woven cotton — of 600 threads per inch — plus two sheets of chiffon, made from polyester and spandex, seemed to make the most effective combination, filtering out 80–99% of the particles, depending on their size.
The team even suggests that the performance of this combination is comparable to that of N95 masks, which are used by healthcare professionals.
Other combinations that perform well, according to the researchers, are tightly woven cotton plus natural silk or flannel, and cotton quilt with cotton-polyester batting.
The researchers explain that combinations involving a fabric with a tight weave, such as cotton, and one that can hold a static charge, such as silk, are likely effective because they provide a double barrier: mechanical and electrostatic.
Yet they emphasize that for these masks to be truly effective, they have to fit very snugly.
“The effect of gaps between the contour of the face and the mask, as caused by an improper fit, will affect the efficiency of any face mask,” they write.
“Our findings indicate that leakages around the mask area can degrade efficiencies by [approximately] 50% or more, pointing out the importance of ‘fit’,” Abhiteja Konda et al.
Physical distancing still crucial
Even the most effective face masks are not the be-all and end-all in terms of avoiding transmission.
“It’s important to understand that face coverings are not 100 percent effective in blocking respiratory pathogens, which is why it’s imperative that we use a combination of social distancing, face coverings, handwashing, and other recommendations from healthcare officials until an effective vaccine is released,” said Verma.
Amato agrees, adding that it’s important to be mindful of the highest risk scenarios for transmission — primarily large-scale gatherings in an enclosed space.
Certain interactions, including yelling and singing, also have the potential to spread aerosol droplets farther than 6 feet.
“Limiting interactions is really how we’ll stop the spread and get back to normal faster,” said Amato. “If you look at areas that are experiencing a spike, you can often trace it back to practices like sitting in a bar while wearing no mask.”
Verma concludes with the hope that this research will help inform people on the best practices for mask wearing.
“We have witnessed some aversion to using face masks, and hopefully the study will help convey that using masks is primarily an effort to protect the most vulnerable members of our society — the elderly or people with underlying health conditions,” he explained.
He concluded, “This is crucial since current estimates suggest that 1 in 3 infected people do not show overt symptoms, and could potentially infect such vulnerable individuals inadvertently.”
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Source: Medical News Today
