All you need is an Instant Pot, a steaming rack, and a small paper bag.
The one catch is it has to be a model with a "sous vide" function. Or another mode that can hold the temperature at exactly 149 degrees. So older models might not be able to do it.
But if yours can, here's what to do.
1. Put a half-inch of water in the bottom of the pot.
2. Grab the steaming rack that came with it, and put it in there. If it's not tall enough to keep the mask out of the water, attach a few binder clips to the rack to act like legs.
3. Put the mask inside a paper lunch bag. Then fold the top of the bag a few times and staple it, or use a paper clip. You can put up to three masks in there at once.
4. Put the bag in your Instant Pot and close the lid. Then select the mode that lets you choose an exact temperature, set it at 149 degrees for 30 minutes and hit start.
That's enough time to sanitize the mask. And when it's done, just take it out of the bag and let it dry for about an hour. The Department of Homeland Security recently did a video on it.