The fluorine and chlorine in R12 and R134a are not free atoms: they are very tightly bound to the molecule. The molecules themselves are very stable, non-flammable, and inert. In fact, the CFCs were considered "wonder chemicals" at the time of their invention because of their safety compared to older refrigerants like hydrocarbons and ammonia.
They will break down under very high temperature, but it's only really an issue if you're doing something like welding in the presence of residual CFC. There's no documented evidence I've ever seen about anyone ever having been injured post-crash from CFC breakdown exposure. You're much more at risk for the fumes from burning polyurethane foam in your car.
These compounds were used for 70+ years in cars without issue and are remarkably safe. The only reason they're being phased out is because R12 depletes ozone (ironically because it's so stable it makes it into the stratosphere without breaking down).
Don't scare people inappropriately.
If I scared anyone, I didnt mean it(your comment actually is inappropriate)- just trying to educate some as to the toxic effects of those halogenated refrigerants. beter to "scare" than to underestimate dangers of working with potentially dangerous chemical compounds, which r12 and r134a are. many peiople coming to this forum are not aware of what the heck they are dioing with refrigerants. better to SCARE than not.
But I do admit although r12 can produce nerve gas, it is as you say, so rare. But I still stick with my original contention that HC's are way less "toxic". No way Hc's can decompose to toxic decomposition agents. Hc's are plain non toxic- thats my point, Tom. Like I warned though- DO NOT SMOKE while handling them.
Yes, I am aware of the history of halogenated carbon skeletons which gave rise to freon. Charles kettering in charge (no pun) of the GM labs discovered it. But funded by DuPond and Ethyl Corp. Much politicking back then to fund what was the heyday of organo halogen research as well as inorganic halogen compounds without which we never would have refined the uranium needed for the atomic bomb. Also, during that time, fluorine chem was in vogue, giving rise to the flawed view that fluorine was beneficial to children's teeth. Now it is understood how toxic fluoride is to bones, kidneys, etc. Back then they were as you say "wonder" chemicals. (read the book Case Against Fluoride). The wonder chemicals as you say, such as r12?? Polychlorinated biphenyls also were considered "perfect" molecules". They also are stable to the tune of about 30 years. Settled in the bottom of the Hudson river now.
DDT was also considered a perfect insecticide. You see, theres a pattern here developing for these what was then "perfect"- now are toxic . The HC;'s of the 1920's they were using are not the same. Now, we use blended gasses with ignition retardants. Much hype still, about 'flammability". So many other risks to one's life during the daily drive to work (read "Traffic").
You want a tough time recharging your ac system?? Use r134a or freon. If you dont evacuate 99.999% of water vapor you WILL generate acid from the vapor and the fluorine/chlorine . Or, you can use HC. Cheap, easy to install, non toxic.