First let me say, that urethanes do some beautiful things. Real CARC just looks so right on these trucks... way better than the pretenders... It is definitely worth being able to use the paint safely.
I was in discussion with another member that works with those that routinely paint with urethanes, and he reminded me of a few things:
First, my experiences with Imron come from the early '70s when respirator use among painters was as rare as hens teeth... dust masks were the norm. Back in those days, painters that used Imron were exposed to so much isocyanate, for such long periods of time, that they quickly developed sensitivity. Today, respirator use is the norm, organic cartridges that are good with isocyanates are cheap and readily available, and careful professional painters can go their entire lives following safety routines, and never develop sensitivity. Very good news!
Second, responsible organizations that use urethanes, train their people to use the safety equipment, set standards on the maximum time a worker may be exposed, and a cartridge may be used, and test their workers, and cartridges, for problems. A worker that is getting unsafe exposure, or is developing sensitivity, will be discovered early. Also very good news!
I am changing my thoughts towards CARC spraying by hobbyists. I have come to the conclusion, that the infrequency of exposure, and the proper use of high quality NIOSH/MHSA organic cartridges, and the use of Tyvek painter's suits, is easily within anyone's capability.
A couple of warnings, however: First, if you can smell paint, you probably have greatly exceeded the PEL for isocyanate. You must wear your respirator the entire time you are around the uncured paint. Second, make sure your respirator fits properly, facial hair isn't letting it leak, and always start with a brand new cartridge. Third, keep an adequate supply of filtered fresh air coming into your paint booth. Skin exposure, is to be avoided too!
Thanks to all for showing off their beautiful results, and prompting me to reinvestigate urethane safety. I apologize for hijacking the thread.
-Chuck