Oz totally regulates gasses? Interesting. Here in the US some are available to the general public without any restriction. The others are still ALL available to the general public--with minor regulation. Various EPA licenses are required to use/possess various gasses, or a resale ID (reseller's tax certificate) allows the purchase
and possession of them, but not the "servicing" of equipment
Traditional "Freon" R-12 requires an EPA-609 certification
that can be obtained in a long afternoon of study & a short test, if you have any familiarity with the concepts. (Probably a single
day if you walked in cold but knew which end of a hose the water
came out of.<G>)
The others are lumped into one more complicated EPA-608 "group", depending on which ones and what capacity...could probably still be a long weekend course to take and pass most of the group, but they structure that from portable systems up to building-wide systems under one umbrella, so there's more to it. That includes traditional R-22 gas.
R-134a is unregulated, at least in the small cans. Would be covered by the EPA-609 for the large cans.
Even the EPA doesn't want to know what is in some of the "magic" brews.<G>