Most of the FC's are highly toxic when exposed to fire.
R-1234yf is not only (slightly) flammable but also releases hydrogen fluoride and carbonyl fluoride when exposed to fire, but this is what is in almost all new cars.
I've run a propane/butane mix in an R12 car before and the fact that it was flammable didn't bother me a bit. The 14 gallons of gas would worry me more than 12oz of propane going up.
Dupont will see that this never sees the light of day. Just like how we don't use butane/propane/CO2 as refrigerants which are just as safe as most of the flourocarbons but have the downside of being too cheap to make any money off of.
https://www.youtube.com/watch?v=1rzFyBdKLvU