I believe they need to be heated to 165°. I remember seeing that they can be steamed or put in the oven for a while at a low temperature. I’ll see if I can find the article since it was very recently that I read it.
Edit:
Here we go:
The infectious disease specialists and hospitalists with AdventHealth recommend against using microwaves or dryers, because they will degrade the personal protective equipment.
“The two methods that I would recommend would be steaming the mask for 10 minutes or placing (the) mask in a low oven at 170 for 30 minutes. These methods have been studied at Stanford but are not yet FDA approved. However, they are probably the best combination of sterilization and equipment longevity” said Dr. Steven Hauser, AdventHealth Hospitalist.
Edit 2
Per the LA Times
The California Department of Public Health recommends frequently washing cloth face masks — ideally after each use, or at least daily. Place the coverings in a bag or bin until they can be washed with detergent and hot water and dried on a hot cycle (or at least washed with hot, soapy water).
If you have to wear the covering again before washing it, wash your hands immediately after putting it back on and avoid touching your face. And throw out any masks that no longer cover your nose and mouth, have stretched out or damaged straps, can’t stay on your face, or have holes or tears in the fabric.
(From later in the article) But even if they don’t provide full protection to the wearer, they can protect others nearby by removing contaminated droplets from the air released by asymptomatic people when breathing or talking.
Research published by Cambridge University Press in 2013 found that homemade cloth masks “significantly” reduced the amount of potentially infectious droplets expelled by the wearer.
Dr. Otto Yang, a UCLA expert in infectious diseases, said he thought universal mask-wearing had helped keep the virus under control in places such as Singapore and Taiwan.
“My personal opinion is that that’s probably been an important thing in other countries flattening their curve,” he said. “If you go to Taiwan or Singapore, everyone’s got a mask on all the time. Healthy or not. Sick or not.”