I've read this at a few places but not here, so here you go. C&Pd from other forums.
Initial article:
http://www.brewracingframes.com/id75.htm
A little research by some forum guys:
Here is the link to the CDC's "Facts about Phosgene" page. Many of the symptoms "Brew Dude" had do not seem to be a result of his exposure to Phosgene, so I question his assertions about them. Nonetheless, we need to remember to be cautious!
CDC Page: http://www.bt.cdc.gov/agent/phosgene/basics/facts.asp
After reading the CDC info it seems to me that it's not just a brake cleaner issue --- but a CHLORINE and Welding (high heat) problem.... I didn't find any info relating to just the chemicals in Brake Cleaner and nothing mentioned about Argon gas. So for me, at least, I'm not going to just discontinue the use of brake cleaner - but any product with chlorine in it.