alot of a/c guy's lately have been getting onboard with that m30 m50 and m60 gas.
Don't let them put it in.
It's pretty much lpg, I know because at lidcombe ice, we've just finished building the first cold storage on a large scale using m50 gas.
The bullshit info and special alarms in place in case of a leak and the warnings we were given if things went wrong are really serious.
Imagine your ac core under the dash springs a leak and you light a smoke
Have a look on youtube about the m50 gas safety tests and see for yourself.
Plus the new flammable gasses have a much smaller particle size so it'll leak from an ageing system far easier.
The so called still ozone depleting refrigerants aren't that much more expensive and less than 500grams is used in any typical a/c system so if your installer say's he wants to put that flammable stuff in... tell him no way.
I don't see why there's such a fuss about the older gasses seeing as in 99% of systems, the gas is recovered and recycled/reused.
Nothing wrong with HC refrigerants, of course you don't just dump it in without getting the system checked and serviced, i have been using it for years without any problems.
How often is a leak found to be in the cabin of a car? Sure the seals in the compressor, orings, schrader valves and lines in the engine bay let go but have you ever seen a system dump it's entire refrigerant supply in 1 go when there is a fault? sure if in an accident or you undo a line it will happen but most leaks are slow and take a long time to allow it all to escape.
As for lighting a smoke... this is why they add chemicals to make the stuff smell so you can detect it, if you smell a gas leak on your bbq do you shrug it off and light it anyway?
As an experiment i gassed an older car system with LPG that i knew had a leak, the car wasn't registered so it wasn't driven and for a couple of days i could smell the gas as it leaked out, this was in summer, cars were started next to it, i walked around it smoking, it was started and moved a few times, plenty of ignition sources were near it and not once did it explode into a fireball, the leak was enough to detect but not anywhere near a suitable stoich ratio for ignition.
That being said i've heard on a few occasions that HC refrigerants when used in a r134 system do tend to leak out (even when a leak couldn't be detected), when regassed with the correct refrigerant the systems have been fine and continued to work for years.