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If you purchase a Reusable Respirator like a 3M 6391 P100: you need new filters for every use. You cannot leave contaminated filters on the mask after you use it. The mask will need disinfection before and after each use. I would drop the used respirator in a bucket of bleach & soap to soak. I can’t say how long the respirator would hold up against a bleach solution though, the elastic straps will not last long.

If your respirator leaks around the edges when you breath in it is worse than useless. If you have facial hair it will leak!
OSAH fit testing: https://www.osha.gov/video/respiratory_protection/fittesting_transcript.html

A full face respirator would provide better protection and the best is an air supplied respirator. Any of these are uncomfortable particularly in hot weather. https://www.osha.gov/SLTC/etools/respiratory/respirator_selection_advisorgenius.html