The original refrigerant was ammonia gas, which is fatal if inhaled. CFCs didn’t kill you if you got a whiff of them.
Unfortunately some of the CFC replacements are flammable and toxic.
No thanks to the ammonia LOL. Even gasoline is a refrigerant as it can be changed to a vapor state and compressed. CFC’s could kill you in two situations which were rare. One is smothering you. The other is doing leak detection with a Halide torch it can put off phosgene {excuse the spelling} gas that can kill you. On the ship I accidentally dumped about 1200 pounds of R-11 in the bilges. I was trying to drain a chill Water Unit to tear it down and the dump valve on the Evaporator had rusted out right where it joined the evaporator. I made it to a forced draft blower for fresh air.