One of the designers who discovered that blue shop towels were more effective at filtering tiny particles than a bandana worked with a particle-testing company to officially test 20 materials.
They tested a variety of things people were using to create homemade masks, from paper towels to vacuum-cleaner bags.
A material sold by an Oklahoma company called Filti wound up testing the best. Filti is advertising this material as being safe for masks.
The company is not an official N95 mask maker, but its "nanofiber" material does block particles more effectively than many alternatives.
After the clothing designer Chloe Schempf and her friends discovered that certain blue shop towels were effective for homemade face masks, the president of a particle-testing equipment company offered to test a wide range of materials for her with the same machine used by N95 mask makers.
They tested products as varied as coffee filters and vacuum-cleaner bags: 20 materials that people on the internet have been using to make masks at home while the worldwide shortage of N95 masks continues.
Related Video: How to Treat Mild Coronavirus Symptoms From Home
Their experiment found that the most effective material for blocking 0.3-micron particles was not, in fact, the blue shop towels, but a "nanofiber" material manufactured by a company in Oklahoma. A swatch of the fabric paired with cotton filtered 84% of particles, the test found. This compares with folded cotton bandanas, which filtered less than 10%.
For context, a commercially built N95 mask filters at least 95% of particles, the president of the particle-testing company, Tom Kennedy of TSI, told Business Insider. Kennedy also said homemade masks could never reach N95 protection because professional mask construction involved precision manufacturing.
Still, capturing 84% of tiny particles was noteworthy. The only other material that came close was a combination of cotton and 3M's Filtrete Furnace Filter, and 3M clearly warns consumers not to use the furnace filter in homemade masks. In fact, the makers of most of the alternative materials, including the blue shop towels, are warning consumers that their products are not intended for masks.
In contrast, Filti is advertising its material as safe for homemade masks and is selling it to the public.
"We designed this — the Filti face-mask material — so people can use it in a cotton mask or they can use it 100% by itself," Filti's founder, Andy McDowell, told Business Insider.
This is notable because right now, there is a worldwide shortage of the typical material used in Centers for Disease Control and Prevention-approved N95 masks. There are only two dozen domestic manufacturers of this material, and some manufacturers say that even with increased production and factories working 24/7, they are sold out through 2020, CBS News reports. Authorities have said existing supplies should be reserved for healthcare workers.
Neither Filti nor its parent company NXTNano is listed as a CDC-approved mask maker.
So what is this Filti stuff?
Schempf discovered the material because a wallet manufacturer that had pivoted to mask making was using it and had sent it to her, she told Business Insider.
Made by NXTNano, the material is typically used in commercial filtering products.
McDowell is also the sales director at NXTNano. He spun off a second company, Filti, before the COVID-19 pandemic to take the remnants from NXTNano's production and turn them into consumer products. He was originally thinking he could sell them to consumers for furnace filters and the like.
But once the coronavirus crisis began, the folks at Filti turned 100% toward consumer mask-making efforts. It now takes NXTNano remnants, cuts them into smaller pieces, and makes one side softer to be more comfortable to wear against the face. NXTNano is also promoting its material as suitable for N95 masks.
NXTNano says the fabric is made from a patented process that spins various types polymers into exceptionally long and thin strands.
"The No. 1 pushback is that people say, 'nanofibers' and the word they will key on is 'nano' like 'nano particles,'" he said. They picture tiny individual fibers, but that's not right. A nanofiber is actually a very thin, long fiber that forms a continuous network, he says. Filti fibers are nanometers across but kilometers in length.
"It's like a bowl of spaghetti but with only one noodle," McDowell said.
McDowell told Business Insider the material was being used in some masks that meet N95 filtration standards, but he declined to say which mask makers were using it, citing nondisclosure agreements.
Business Insider could not verify that this fabric has achieved any kind of formal approval to be used in masks; however, some researchers are generally studying the use of various forms of nanofibers in N95 masks, and scientists in South Korea have been experimenting with nanofiber mask making during the COVID-19 worldwide shortage. Other nanofiber equipment vendors are also advertising the material as suitable for masks, but they are not selling the finished fabric to the public.
What is clear is that the particle testing done by TSI was conducted independently from Filti. Schempf simply gathered a bunch of materials she had heard about, including the Filti samples sent to her by the wallet company, and sent them to TSI. TSI tested them "blind," Kennedy said, meaning it didn't know which fabric was which.
All of this means there's no objective evidence that Filti's fabric is safe to use for hospital-quality masks, as its makers claim, but there is evidence that it filters far better than a cotton bandana.
Filti is selling its fabric from its website for $30 for 21 square feet, which the company estimates is enough to sew 50 to 80 masks, depending on their size.
These masks cannot be washed, McDowell says. He says they can survive being in the oven for 30 minutes at 150 degrees, but there isn't solid research to show this is a safe and effective method to sterilize a mask, particularly if it has actually been exposed to COVID-19.
The CDC advises that wearing a bandana outside is far better than wearing nothing, as this could keep a sick person from widely spreading their germs. A well-fitting mask with better filtering should protect someone better than a bandana, however, says TSI's Kennedy. And that's why home mask makers like Schempf have been on a mission to find materials that filter well, are breathable, and can be bought by the public, at least until the N95 mask shortage is over.