Here’s how long reusable COVID cloth masks are effective

• A new study found that washing and drying reusable cloth masks can still work after several washes.
• After 52 washes, cloth masks still effectively filtered the virus out.
• Cloth masks offer some of the best protection against COVID-19.

After the Centers for Disease Control and Prevention recommended that fully vaccinated Americans return to wearing masks in public indoor places earlier this summer, you may have found yourself wondering if your cloth mask from last year was still worth wearing.

Don’t throw them out: Those masks will still work fine, according to a new study.

Researchers from the University of Colorado Boulder found that washing and drying reusable cloth masks doesn’t reduce their ability to filter out viral particles. Even better, reuse can also help reduce worldwide garbage, as an estimated 7,200 tons of medical waste have been generated every day since the start of the pandemic.

“It’s good news for sustainability,” Marina Vance, assistant professor at the University of Colorado Boulder, said in a statement. “That cotton mask that you have been washing, drying and reusing? It’s probably still fine — don’t throw it away.”

Your mask can last a year

The study, published in the journal Aerosol and Air Quality Research, aimed to find out how washing and drying impacts reusable cloth masks. Masks should be washed frequently and at a certain temperature to keep wearers protected. 

Vance and her team created double-layered squares of cotton and put them through repeated washing and drying up to 52 times, or the equivalent of a weekly wash for a year. They were tested about every seven cleaning cycles, according to the study.

Although the masks were not tested on real people — they were mounted on steel in a controlled environment — researchers used real-life conditions, such as high humidity levels and temperature changes, as if they were being used through four seasons.

Despite the cotton fibers fraying over time, researchers said that repeated washing and drying didn’t significantly affect the cloth’s effectiveness at filtration. They did note that it was a little harder to inhale through the cloth by the end, though.

There is a caveat to the study: There must be no gaps between the mask material and the wearer’s face, Vance said. Previous research found that when masks don’t fit properly, you’re not getting the best protection, so it’s important to make sure your mask still can fit comfortably over your nose and mouth.

This is the mask you should wear

Research found that the N95 masks were the best against Covid-19, followed by cotton masks or surgical masks. Coverings like neck gaiters and bananas were not as protective but still remained a staple for people.

And hammering down on the point, the CU Boulder researchers said that they found cotton cloth masks filtered out up to 23% of the smallest particle size on which the virus can travel, far more than bandanas, which filter only 9% of particles.

Still, the best masks remain N95 and KN95 masks, which filtered out 83% to 99% of particles, while surgical masks can filter out up to 88% of tiny particles that can carry the coronavirus.