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Author: Kelsey Simpkins, University of Colorado Boulder

Reusable cloth masks that people have been using for the past year or more may look worse. But new research from the University of Colorado at Boulder found that washing and drying them does not reduce their ability to filter out virus particles.

"This is great news for sustainable development," said lead author Marina Vance, assistant professor in the Paul M. Rady Department of Mechanical Engineering. "The cotton mask that you washed, sun-dried, and re-used? It's probably okay — don't throw it away."

This study, published in the journal Aerosol and Air Quality Research, also confirms previous research, that a layer of cotton mask on a surgical mask-which fits the face correctly-provides more protection than cloth alone .

Since the beginning of the pandemic, an estimated 7,200 tons of medical waste have been generated every day, most of which are disposable masks.

“At the beginning of the pandemic, we were really annoyed. When we went out for a hike or went to the city center, we saw all these disposable masks littering the environment,” said Vance, who is also an environmental engineering project faculty member. .

Therefore, when scientists at the nearby National Renewable Energy Laboratory (NREL) contacted her to study how washing and drying affect reusable cloth masks, Vance was eager to join forces.

Their process is very simple: make double-layer cotton squares, wash and dry them repeatedly (up to 52 times, which is equivalent to once a week in a year), and test them between approximately every 7 cleaning cycles.

Although these masks were not tested with real people-they were installed at one end of a steel funnel, through which researchers can control the consistent flow of air and particles in the air-the researchers tested the masks using real-to-life conditions , High humidity and temperature to simulate the effect of our breathing on the mask.

Although cotton fibers began to decompose over time after repeated washing and drying, the researchers found that this did not significantly affect the filtration efficiency of the cloth.

The only significant change is a slight increase in inhalation resistance, which means that after some wear and tear, the mask may feel a little harder to breathe.

A key caveat is that they tested it in the lab using "perfect fit".

"We assume that there is no gap between the mask material and the human face," Vance said.

Everyone's face shape is very different. Therefore, depending on the shape of the mask and how well people adjust it, it may or may not fit. Previous studies have shown that an unsuitable mask can allow up to 50% of the airborne particles and viruses we breathe and exhale to pass through.

So what kind of mask should I wear?

This study is not the first to find that cloth masks provide less protection than surgical masks or a layered combination of surgical masks and cloth masks.

Measuring the effectiveness of masks in filtering inhaled air-protecting the person wearing the mask, rather than reducing the source of transmission-this study found that cotton masks filter out 23% of the smallest particles (0.3 microns) where the virus can spread. The turban filters even less, only 9%.

In contrast, surgical masks filter out 42-88% of tiny particles, while the cotton mask on top of the surgical mask achieves a filtration efficiency of close to 40%. As expected, KN95 and N95 masks performed best, filtering out 83-99% of these particles.

However, although this study found that compared with layered methods or disposable masks (such as surgical masks, KN95 and N95), cloth masks alone provide less virus protection, but for those who rely on cloth for comfort and affordability And for people with reusability, this is still important information, Vance said.

"I think the best mask may be the one you really want to wear," Vance said. "And it will cling to your face without being too uncomfortable." Further exploration of Sneeze cam reveals the best fabric combination for cloth masks. More information: Sumit Sankhyan et al., filter performance of layered masks and face masks, and cotton Study on the reusability of high-quality masks after repeated washing and drying, aerosol and air quality (2021). DOI: 10.4209/aaqr.210117 Citation provided by the University of Colorado at Boulder: Reusable cloth masks remain unchanged after one year of washing and drying (2021, September 9), November 2021 Retrieved from https://phys.org/news/2021-09-reusable-masks-year.html on the 22nd. This document is protected by copyright. Except for any fair transaction for private learning or research purposes, no part may be copied without written permission. The content is for reference only.

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