After reading this i think Random Orbital Bob is hitting the right topic, but I want to emphasize that
1) DUST PROTECTION and
2) SOLVENT PROTECTION
are two totally DIFFERENT THINGS!
The P1-P3 rated filters are for DUST protection, i.e. they inhibit small, tiny and extremly tiny particles to enter the air the breathe. However, THEY DO NOTHING FOR THE SOLVENTS OR GASSES!
Any paint that has ANY kind of solvent in it requires ALSO GAS/SOLVENT protection! So are then the filters rated A1-A3 (at least for Scott Safety, I've not ye met any M-rated filters - I do know M-rater vacuum cleaners, but they are ONLY also rated for DUST, i.e. small particles).
If you do paint jobs, please get a combination filter - I'm using SCOTT as an example here;
https://www.scottsafety.com/en/emea/Pag ... on+Filters
but any band will do as long as it has the combination. Especially spray painting with solvent based paints is dangerous business, as you will have
1) both particle contamination in the form of micro small DRIED paint particles
2) gasses in the form of solvents that vaporized into the air.
The solvents used in paints are really toxins. Water based paints are actually NOT ANY BETTER - the stuff that makes the paint resists for example mold is pure poison. They however smell significantly less, so you are less likely to start feeling ill as quickly, but you are still in the danger zone - often without realising it. The nasty bit is that since it is diluted to water - it will enter your body VERY quickly, since your body is 75% water. So, even if you are using WATER based paints you should still use a combination filter! The whole business of spray painting is about atomization - making the paint as small as possible, so that it will enter the surface to be painted smoothly. Unfortunately - as by product you will contaminate the air.
More info on solvents from Wikipedia;
http://en.wikipedia.org/wiki/Solvent
A lot of the stuff used for paints are really toxic compounds. Quote from wikipedia on the health section;
"General health hazards associated with solvent exposure include toxicity to the nervous system, reproductive damage, liver and kidney damage, respiratory impairment, cancer, and dermatitis.[13]"
(edit: spay -> spray)
Additional thing is the usage of Px rated filters with a small active carbon filter added to them, like AirAce. The active carbon in these filters is NOT sufficient vapor/solvent protection. They only remove some of the smell, nothing else. Since the smell works as an alarm indicator, you're actually worse off since you'l anyway inhale (at least some) of the vapours/solvents without realising it.