Particulate size is going to be the biggest issue, as danger and size are directly related--- I wonder if some packing tape and a cell-phone microscope wouldn't work: Ozcan's LUCAS (cellphone microscope) papers are here: http://innovate.ee.ucla.edu/refereed-journal-publications.html#DOI_101039C000453G

here's the specific article that includes characterizing Particulate Matter: http://pubs.rsc.org/en/Content/ArticleLanding/2010/LC/C003477K

Packing tape is a good idea. I am interested in the laser technique because it would be realtime and wouldn't "run out" like when the packing tape is used up.

we could go "reel to reel" with the tape, taking readings right after particulate exposure. it wouldn't be real time, or last forever, but It would also create an analog, material artifact of the testing, which is good for verification/chain of custody.

Just want to remember this idea: small good-sized first-surface mirrors can be found in scanners, and I'm planning to take one apart to get them out. One reason the above test didn't work well was because I didn't have good quality mirrors. First surface mirrors would be especially good because they have no glass in the beam path -- they're just bare silvered surfaces.