Starting May 1, Illinois will require everyone over age 2 to use a mask when they can’t maintain a 6-foot social range in public. N-95 masks, which are in short supply, are best booked for health care employees, who enter direct contact with COVID-19 patients. What material or mix of materials is finest for homemade masks?
A new study carried out by University of Chicago professor Supratik Guha and coworkers at Argonne National Laboratory in Lemont looked at more than 15 common family materials to see which were best for protecting against the coronavirus that triggers COVID-19
More particularly, the study examined the fabric’s purification performances against the small droplets that are how COVID-19 and other breathing diseases are spread out. Using a mask or a fabric facial covering minimizes the transmission of these breathing droplets from a contaminated person, Guha states.
Guha and his group finished the research study over 2 weeks after he began seeing news reports that the Center for Disease Control and Prevention and various states had begun recommending using fabric masks.
“I saw that this was coming,” he says. “At that point, we also understood that there was really little clinical information on the efficiency of (fabric) masks. … We went through seven or 8 days of intense experiments and analysis that went on through the night; the data would be taken during the day. I believe we felt that we wished to get this data out in public rapidly. That was the crucial objective, and that’s what we did.”
His group likewise tested an N-95 respirator and surgical masks for comparison. They also looked into the efficiency of numerous layers of a single fabric and a mix of numerous fabrics.
They found the most reliable fabrics to be cotton, natural silk and chiffon; synthetic silk and satin did not supply as much protection. Hybrid mixes, such as high thread cotton, in addition to silk, chiffon or flannel likewise supplied broad filtering coverage.
The study notes, “Fabric with tight weaves and low porosity, such as those found in cotton sheets with high thread count, are more suitable. For instance, a 600 TPI (thread per inch) cotton performed much better than an 80 TPI cotton. Fabrics that are porous should be avoided.”
Despite silk and chiffon’s sheerness, the 2 fabrics were surprisingly effective, especially four layers of silk, such as a folded scarf.
Guha states chiffon and other products that have electrostatic properties can in fact act as a barrier to the tiny droplets.
“What we found was that some of these materials are respectable,” he stated. “Utilizing a mix of cotton and these products is the very best. A quilt, a mix of polyester and cotton likewise had outstanding filtration.”
Breaking News Newsletter
As it happens
Get updates on the coronavirus pandemic and other news as it happens with our breaking e-mail alerts
Two chambers at Argonne were utilized to carry out the research study. In the first chamber, Guha and his group generated aerosols with dry particles of salt chloride, a standard approach in respirator screening. From there, a PVC pipeline caused the collection chamber, which is where the material was kept in place by clamps. The collection chamber had a fan that sucked the air, so it streamed from the generation chamber to the collection chamber. Guha stated they utilized specialized equipment that determined the density of the particles upstream and downstream of the fabric.
“What was special in our work was the devices utilized to measure particles of 10 nanometers, which is about a couple of thousand atoms,” he says. “We were able to measure the purification effectiveness at different particle sizes, going all the way from a couple of thousand atoms to 6 micrometers range. A human hair is approximately about 75 micrometers in diameter, so 6 is a little less than one-tenth of that.”
Something that shocked Guha throughout this study was the result of gaps in masks.
“Our studies also suggest that spaces (as brought on by an incorrect fit of the mask) can result in over a 60 line in the filtering performance, suggesting the need for future fabric mask design research studies to take into account concerns of ‘fit’ and leak, while enabling the breathed out air to vent effectively,” the study states.
He says that if a mask does not fit effectively, it’s not much usage. Masks should fit with very little gaps, but exhaled breath should be able to come out or else the user will take in co2.
