N95 masks are roughly $1 each in the 20 pack at the local hardware store. I wouldn’t throw them away though, not in a SHTF situation in which no more can be obtained. I’d expose then to sunlight for several hours on each side, set aside used ones for a month or more in a dry location, and then use them again once I ran out of new ones. New is far better than used, but used is far better than none.
If you can heat them to 60 deg C (140 F) for 60 minutes it would sterilize them adequately for ebola.
30 pack for $8.00 + shipping on Amazon
Microwave the used masks?
Yup, or even a douse-and-dry in bleach should work. When the SHTF, discarders will be chastised, at least by me.
You can buy N100’s and P100’s as well for added filtering.