Cotton masks that have become slightly damp through human breath are on average nearly 35 percent better at capturing grains than when dry, making them superior to synthetic masks to stop the spread of COVID -19, according to a new study.
Synthetic masks showed “no performance change” in stopping grains when they were damp and thus “performed poorly” compared to cotton, the U.S. National Institute of Standards and Technology (NIST) said of their study.
“This new study shows that cotton clothing actually performs better in masks than we thought,” NIST research scientist Christopher Zangmeister was quoted as saying on the NIST website .
Cotton cloth absorbs very little of the water in a person’s breath, creating a humid environment inside the mask. As microscopic particles pass through, they absorb some of this moisture and grow larger, making them more likely to get caught in the mask, NIST explained on its website when announcing the news.
Most synthetic fabrics, however, are water-resistant and do not absorb moisture, meaning that they do not have the seeding efficiency, a measure of how good a material is. capturing grains, changing in humid conditions, NIST said.
The study tested a range of double-layered swatches of clothing under conditions similar to a person’s breathing humidity, allowing researchers to read measurements that more accurately reflect how clothing performs when a person live, their breath, NIST said on its website.
They placed the swatches in small boxes where the air was maintained at 99 percent humidity so that the swab would have a chance to become as moist as a person’s breathing. For comparison, a second set of swatches was also prepared at a humidity of just 55 percent.
All the swatches were then placed in front of a pipe that released air at the same rate as the breath.
Researchers then measured the number of particles in the air before and after passing through each fabric.
The new measurements show that, under humid conditions, seeding efficiency in nine types of cotton flannel increased from 12% to 45%, with an average increase of 33%, NIST said.
The six types of synthetic fabric tests included nylon, polyester and rayon. All six did not perform well compared to cotton flannel, NIST said.
Researchers noted that medical grade masks and N95 respiratory masks “provide the same filtration efficiency under high and low humidity conditions”.
The study was conducted by NIST and the Smithsonian Museum Conservation Institute. Published in ACS Applied Nano Materials.