We actually bought 2 UVC light bulbs just to sterilize my masks. We only have a handful, and believed early on that UVC could make them reusable, but have no proof.

But using them is very hard. They produce ozone which is harmful to your lungs, and the light themselves are harmful to your eyes and skin. So I don't have a safe way to set this up yet. Now that we are all quarantined maybe we can have more time to figure out a sustainable way to use it.