From the perspective of someone who has worked around isocyanate hardeners since they were introduced 40-something years ago, let me pass on some warnings. A GOOD respirator is an absolute must, but it only slows down the process of exposure to the cyanide compounds. An air-supplied "shoot suit" that covers ALL exposed skin is the safe way to shoot any type of isocyanate, since it's also absorbed directly through the skin.
A lot of my oldtime painter friends complain of having "bugs crawling under my skin" after spending years shooting paint with hardener added. An occasional exposure might not be terribly harmful, but like any cumulative poison, whatever gets absorbed into your body NEVER goes away!
Jerry
