I posted this on another forum, but it is probably appropriate here.
I just attend a Glock Certified Armorer's class in Nacogdoches, Texas. Our instructor, Erich Clark, told us about an incident where a gentleman used brake cleaner to clean his gun, fired it and inhaled some white smoke that lingered a bit and suffered some serious and long lasting health issues. Frankly, I had my doubts about the accuracy of the story, but I was trying to find a reference to the type of gas that is produced and ran across this post on the internet:
http://www.brewracingframes.com/id75.htm
The gas is Phosgene gas and it is very serious stuff. Now I use Brake Cleaner products, and I will have to say that Erich's story sounds much more plausible to me now, although the gentleman in question would have had to use the product almost immediately before firing his weapon. All of this stuff I have used evaporates very very quickly.
I am not one to go into a panic because a product contains something that may be harmful, but this bit of knowledge could be useful. Apparently the compound that can produce the phosgene gas under the proper circumstances is tetrachloroethylene, so forewarned is forearmed.
Not all Brake Cleaners contain this compound. For example Non Chlorinated Brakleen by CRC contains only Acetone, Naphtha, and alcohol (per their MSDS sheet). This is what I use.
Per Erich, halogenated cleaners should be avoided for use on Glocks. I would assume the same to be true for other polymer framed guns.