I sterilize my N95/KF94 masks with UV light for reuse.

If anyone wants to follow suit, beware fake UV bulbs. Test your product / bulb with a banana.

Put masking tape on the banana, then expose the banana to the light for a few hours. If the band develops a suntan except for under the tape, you've got a good bulb. It should kill any bacteria and certainly any viruses on your mask.

But still throw out your masks when the fit gets bad; a mask is useless if the COVID is slipping in through the sides.