John all good questions and also a good reminder to all of us to increase our safety efforts. It is hard to replace a good fit test considering how many fit tests fail. The less than perfect but common short cut fit test is to keep you mouth closed and breath in slightly and see if it creates a vacuum you can feel on your mask. As far as filters go they are breathing all of the time so store them in a sealed bag and if in doubt replace them. The filters should come with a recommended replacement period. I think filter replacement is probably a bigger actual issue in respirator use than fit test and I would guess 50% or more of our respirators would not pass a simple fit test. I would love to hear an experienced safety engineer chime in on this one.