We use the non-valved N-95 masks while cleaning up in New Orleans. They are less comfortable than the valved ones, and the fogging makes wearing glasses darn near impossible. But, they are cheaper than the valved ones (you can get them by the box-full at Lowe's), which is good since they usually have to be pitched after a few hours use. But for the purposes we are discussing, that should be sufficient.

I have two of these masks in my "just-in-case" pouch in my briefcase. ( I don't like the term "Bug-out", as in Bug-Out Bag. Reminds me of the rabbit scene in 'Monty Python and the Holy Grail': "Run away! Run Away! Run Away!..... King Arthur was Equipped to Survive. Brave Sir Robin, well, he Bugged Out.)

.....CLIFF