You might be able to use UV-C light sterilization. Strangely, these types of lights are all suddenly sold out on amazon, wonder why... https://www.amazon.com/gp/product/B07W1PHS9P/ref=ppx_yo_dt_b...

Remember that light can only sterilize the surfaces it contacts. It can not sterilize beneath the surface.

So if droplets containing viruses penetrate beneath the surface of the mask, sterilization with light will not be able to reach them.

Obviously something like this would only make sense under extreme circumstances, when you have to leave the house, but can't use a fresh mask every time, because of shortages.

An N95 isn't going to survive an autoclave...

I think my P100 filters might survive an autoclave. They are the pink disc kind from 3M. Pressure cooking only goes up to 121C @ 15psi, so it isn't as hot as it may seem.

It's not just the pressure and the temperature, it's also the steam. Autoclaves are are pretty nasty environments, and I wouldn't trust a filter that had gone through one. It's very likely the filter medium would have been degraded.

I assumed the reason not to re-use them is that the paper mask structurally wears out and no longer creates the proper seal on your face.

what about the P100 filter cartridges used on half/full face respirators? Those have a plastic skeleton with a rubber gasket.

They last indefintely, i.e. change the filter when it becomes clogged, which will be approximately never if you're not actually using it in a dusty environment. But check the manufacturer's instructions.

What if you microwaved it? To be clear, I don't have any idea if this works or not, I'm just asking. And of course it couldn't have any metal parts.

That works for sponges but it breaks the material down pretty fast. You could possibly use ozone to sterilize the masks if you sealed a container and let it sit at a proper concentration for the correct time period.

I heard a report that soaking them in salt water and allowing it to completely dry can destroy viruses as the salt crystals from. YMMV. Web search for more information.