Understanding Respirators (or: clean air, explained from a New Jersey perspective)

in a post on Wesleyan's Anonymous Confession Board, people started talking about protective equipment and respirators (with regard to spraypaint and enclosed spaces) and people started asking about the filter rating system. so. here's what I know.

filters are rated with a letter then a number, like P100 or N95. the number represents the tightness of the weave, so to speak. i.e., the higher the number, the smaller the particles it captures. the N and the P designate whether or not oil based aerosols can get through the filter. N does *not* block them, P does.
So. Hospitals carry a lot of N95's, because an N95 is sufficient to block the transfer of certian microbes, e.g. Tuberculosis. But a P100 will also block these. For asbestos, for another example, you want a 100 rating.
I rock a P100 because, why not? They're a little more expensive, but it's worth it because the protection is more comprehensive.

But that rating system only covers the filter element itself. There are also pre- and post- filter elements that come into play. The filters I use most often are called GME-P100. No idea why the GME nomenclature, but in addition to a p100, it has a layer of activated charcoal. The kind of stuff they give you if you swallow poison or OD--activated charcoal can neutralize a lot of organic toxins (wikipedia it, it's cool stuff). In a respirator filter, this is most often marketed to petroleum refinery workers and the like--people exposed to toxic hydrocarbon vapors. They also prevent smells from getting through (which was a fucking god-sent in NOLA).
In non industrial conditions, you can probably rock a filter for a few weeks of use before you have to retire them. Filters are replaceable, so, my respirator from all of my New Orleans work is not toxic, just needs new filters.

FIT IS THE MOST IMPORTANT PART OF A RESPIRATOR. make sure that if you cover the air-intake-holes, you're unable to breathe. otherwise you have a leak.
3M makes a nice cheap series of respirators. I have a thin face, so the 3M's don't fit. I have a slightly more expensive but worlds more comfortable respirator made by MSA, and it's probably saved my life, or at least my lungs. It's also a fashionable shade of blue.
If you're interested in buying a respirator, ProfessionalEquipment.com sometimes has decent deals. Hardware stores also carry them on occasion, though usually only one brand/type.

When do you need a respirator?
if you go into the Wesleyan maintenance tunnels, you should have a p100. some but not all of that tunnel system has a lot of asbestos. If you're doing a lot of spray painting in an enclosed area, rock a pXX. If you're using solvents and the like in an enclosed area, err on the safe side and get some activated charcoal P-somethings. You should also wear one when soldering, especially if using lead-based solder.
Seriously. I do stupid shit all the time. I should know.