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Sunlight not an effective face mask disinfectant

When I come back from places like the grocery store, I hang my face mask outside in the sunshine for several hours. Is that a good way to disinfect my mask?

— Sarah, Ashland

Ultraviolet light from the sun does have virus-killing properties, but probably not enough to safely disinfect your mask.

Bill Anderson, a UV light expert and chemical engineer, said sunlight has UV-A, UV-B and UV-C rays. Both UV-A and UV-B can damage skin and cause skin cancer, but most UV-C rays get blocked out by the Earth’s ozone layer.

It’s those UV-C rays that you need for their ability to damage and kill the COVID-19 virus, Anderson said.

UV-C emitting machines can be used to kill viruses and other pathogens. They are most often used in unoccupied spaces because the radiation can damage human skin and eyes, Naomi Millan, senior editor of Building Operating Management, wrote in 2020 for an article about ultraviolet light and coronaviruses.

The federal Centers for Disease Control and Prevention recommends washing reusable masks after every use. Always wash your hands after handling a used mask.

Masks can be thrown in with your regular laundry in the washing machine and washed with regular detergent, the CDC says.

If you wash your mask by hand, use one-third cup of household bleach per gallon of room temperature water and let the mask soak in the bleach solution for at least five minutes. Rise it thoroughly with cool or room temperature water, the CDC says.

To prevent a potentially harmful reaction, don’t mix bleach with ammonia or other cleansers. Color-safe bleach may not be suitable for disinfection, the CDC says.

When choosing a washing method, remember that regular bleach can discolor a colored mask.

To dry a mask, use the highest heat setting in your dryer until it’s completely dry, or allow the mask to air dry completely — preferably in direct sunlight, the CDC says.

Send questions to “Since You Asked,” Mail Tribune Newsroom, P.O. Box 1108, Medford, OR 97501; or by email to youasked@rosebudmedia.com. We’re sorry, but the volume of questions received prevents us from answering all of them.