Besides the flammable aspect of alot of the "alternative" refrigerants to an unsuspecting repair tech/ new owner, they can damage an expensive AC recovery machine, sometimes beyond repair. We went through this problem big time during 134a to 12 changeover. Had to buy very expensive refrigerant identifiers to try to save machines. Didn't really think this problem still existed !! I get 134a for $4.99 a 12oz can. Most later model systems hold around 2lbs. or so. Being a shop owner is probably why I made comment. Pertains mostly to guys everyday vehicles, I guess.
