Reusable sheet masks can be effective for up to a year, study finds

Reusable sheet masks can be effective for up to a year because washing and drying does not reduce their ability to filter out viral particles, study finds.

The finding, published in the journal Aerosol and Air Quality Research, also confirms previous studies that layering a cotton mask over a surgical mask – snug against the face – offers more protection than fabric alone.

“That’s good news for durability. That cotton mask that you washed, dried and reused? It’s probably still fine, don’t throw it away,” said lead author of the study Marina Vance, assistant professor at the University of Colorado. Boulder in the United States.

Since the start of the pandemic, around 7,200 tonnes of medical waste has been generated each day – much of which is disposable masks, the researchers said.

“We were really bothered when the pandemic started, going out, and seeing all these disposable masks littering the environment,” Vance said.

The researchers created double-layered cotton squares, subjected them to repeated washing and drying for a year, and tested them every seven cleaning cycles or so.

The masks were mounted on one end of a steel funnel through which the researchers could control a constant flow of air and airborne particles.

They tested the masks in realistic to real-life conditions, with humidity levels and high temperatures to mimic the impact of our breathing on the mask.

While the cotton fibers began to fall apart over time after repeated washing and drying, the researchers found that this did not significantly affect the filtration efficiency of the fabric.

The only noticeable change was that the resistance to inhalation has increased slightly, meaning the mask may feel a bit harder to breathe after some wear and tear.

A key caveat, the researchers noted, is that they performed the tests using a “tight fit” in the lab.

“We assume there is no space between the mask material and the person’s face,” Vance said.

The study found that cotton cloth masks filter out up to 23% of the smallest 0.3 micron particle size the virus can travel on.

Bandanas filtered even less, at just 9%.

In comparison, cotton masks on surgical masks achieved a filtration efficiency of nearly 40%, the researchers said.

The KN95 and N95 masks performed the best, filtering out 83-99% of these particles, they said.

While this study found that fabric masks on their own offer less protection against the virus than a layered approach or disposable masks, this remains important information for those who rely on the fabric for its comfort, price. affordable and reusable, Vance said.

“I think the best mask might be the one you’re actually going to wear. And it’s going to fit your face perfectly without being too uncomfortable,” Vance added.