Hey db sonic,

Industrial Hygiene is my career; after a ton of study, what I found was that once the urethane is catalyzed and set, it prevents very little hazard. It's typically the isocyanate catalyst that's the problem, before and when spraying.

And thats the the trick you can manipulate. If you use a brand new combination HEPA and organic vapor cartridge on a respirator, you can filter out the particles/chemicals that are mixed and about to polymerize. For the amount of spraying we do, this is adequate along with skin protection.

Been there, done that and monitored it.

i like urethanes, but also respect them. Caveat-if you get allergic to any given urethane or epoxy, for that matter, very small amounts will give you that "peanut allergy" response. Most people don't experience this, however.