Reggie,
When in doubt, err on the side of caution.
Your local OHS government department can provide you with, or direct you to, MSDS sheets for whatever substance you're using.
Personally, I always use a 2 stage organic filter cartridge in my respirator when I'm painting.
I sometimes get burning eyes when I cast a lot of resin in a sitting - better ventilation would be a good idea - like the exhaust fan over my stove.
But as resins contain di-isocyanates (some can be very bad indeed), again, err on the side of caution.
Remember, asbestos was man's best friend at one stage.