Brake cleaner is some scary stuff. I love it for its ability to clean but alot of care must be taken with it.

When heated it can actually turn into toxic gases including phosgene if mixed with argon gas, like could easily happen if you use it to clean a metal part before welding. This is something I used to do alot until I learned about it from this article
http://www.brewracingframes.com/id75.htm

Be careful out there!