That's interesting, I generally use a 3M 6502QL mask with p99 filters, and I feel like I get pretty good protection against everything, even with a beard. Mark talked me into using a mask while brazing, and at least I don't get discolored nose discharge like I used to. And I always use it while using powered woodworking tools. I have pretty good dust detection because I'm an asthma sufferer and dust/smoke really messes me up. That's why I didn't think I needed a mask to braze, it didn't really affect me so much.

But I hate sanding, so maybe I don't do it enough to have a problem.