The filtration doesn't run out when working with particulates, it actually gets better. The reason you have to replace them is they get too good at filtering an

The filtration doesn't run out when working with particulates, it actually gets better. The reason you have to replace them is they get too good at filtering and it restricts natural breath (or they get damaged). In this situation, you assume the mask catches particles containing coronavirus. The mask becomes a biohazard pretty quickly. They could probably be safely disinfected and reused.