Be absolutely certain you know what you're getting involved with and the potential dangers. This quote is from another forum on the subject of alternative refrigerants.....

R12A is a hydrocarbon that is extremely flammable. You might recognize it by its more common name PROPANE. It will contaminate your entire system, and once contaminated, everything will need to be replaced, if you want to convert it back. The problem with R134A is that the smaller molecules of the gas, can penetrate the old rubber hoses, and that you also need to change the oil, flush the entire system of the old oil, and re-hose the entire system with barrier hose, if you want to do it correctly. With air conditioning, there are no short cuts, and using the wrong products devalues your car. It is your car, and you are free to do as you like, we can only advise you. I have seen how volatile an engine fire can be when the air conditioning hoses burn through, and the oil in the refrigerant lines starts to burn. It is like a flame thrower. I can image the same scenario with PROPANE in place of the R12 or R134A refrigerant. I can hear it now, when the flames hit the PROPANE, the flames will travel through the hoses, and all the a/c system will go BOOM, like a hand grenade. Don't want to be anywhere near when that happens.