NHRA Welding rules??

IQ52 said
The man is right. Clorinated brake cleaners produce poison phosgene gas when heated.

http://www2.worksafebc.com/i/posters/2013/ws_13_09.html

As a guy who used to work with stuff like R12, 22, 502 and even some R500, I can tell you all about phosgene. I'm not sure there's much in the way of brake clean that's chlorinated anymore, since the ban of these refrigerants.