So what do the supermarkets do with all their R-134a they have on the shelf known to most people as 'Blow off Canned Air'?

Also what do they do with their old refrigerants once they are removed?

BTW Propane is known as R-290.

Dust off brand Canned air is 1,1-Difluoroethane R-152a

Propane is also labeled as R-22A and has very similar properties to R-22.Most HVAC techs are opposed to using hydrocarbon refrigerants because of their flammability. Probably not all that dangerous but you will have to watch what you are doing, especially if your are sealing leaks with a brazing torch. The other problem is that you don't have to have EPA training and an HVAC tech license to buy propane (at least not yet).

Personally I have been playing with propane as a refrigerant for years just using the common cheap stuff out of my 20# tanks and yes it does work super!

As for safety I don't see it as being any different than working with any other flammable gas or fuel system being I have been running propane powered vehicles for about 15 years now.

"Playing with propane" and "probably not all that dangerous" are statements I must take issue with; they are dangerous; their use is strictly controlled by codes and standards.

I Googled "propane explosion" and got 9.3 million hits. One from

LawyersandSettlements.com which included the following:

Propane is an extremely flammable gas that must be handled with absolute care. It is a heavy gas and can accumulate in low lying areas such as basements and floors, resulting in an explosion. Even when contained in cylinders, propane gas can build up pressure when exposed to extreme heat and can rupture the tank and explode.
Propane is a colorless and odorless gas which is intentionally odorized so that leaks can be detected. The odor is similar to rotten eggs. If you smell a gas leak in your home, RV or boat, you should extinguish all cigarettes and other sources of ignition and leave the premises immediately. Do not use any electric switches, appliances, thermostats or telephones that may cause a spark. Close the gas shutoff valve on the propane tank or cylinder. Call your propane supplier or fire department from a cell phone or a neighbors phone. Have a trained professional investigate and repair the leak.
Although propane is stable when exposed to air or moisture, you must avoid using propane near sparks, open flames or even a static charge.

The EPA endorsement is for very limited and controlled applications which do not include "playing" with propane as a refrigerant.

"Although propane is stable when exposed to air or moisture, you must avoid using propane near sparks, open flames or even a static charge."

Yes and my wife has about 20#'s of assorted cans of pressurized items, cosmetics and alcholes in our bathroom that have similar to worse flammability characteristics.

Then there is that closet of cans of assorted spray type cleaners and paints that also have similar flammability ratings too.

Or what about that cabinet of hard liquors and drinkable alcohols that keep so many people happy?

Or the multiple 1# propane bottles for the portable cook stove or the butane lighters and their refill cans or the 1" dia line that runs under my house feeding my furnace and stove and former water heater from a 1000 gallon tank but the government and EPA doesn't seem to care about those being in my house.

What I am saying is the 3 - 4 pounds of propane that would be contained in a central air system, which is designed to hold far higher pressures than any spray can propane tank or gas line and are not known for developing rapid explosive leaks, is far safer than the dozens of other moderate to highly flammable pressurized cans of other stuff that are legally allowed to be kept in any quantity in most anyones house.

If people want to play the safety card they have to play it equally and unbiased against all items of equal or similar hazardous potentials found in said locations and not pick and choose what they are going to deem to be acceptable risks or not.

True honest unbiased safety is a all or nothing concept. Anything else is just acceptable risk based on probability and I can live with that.

The source you chose to quote, lawyers and settlements, pretty much tells the tale. In my opinion, the basically unconstrained excess production and release of lawyers is a hell of a lot more detrimental and dangerous to the general public than the use of propane as a refrigerant. Most air conditioners that develop leaks do not so so catastropically, but usually leak slowly from pinholes that take months to release a few pounds of refrigerant. That hardly constitutes a risk of catastrophic explosion or conflagration. Also, if not mixed with the correct amount of oxygen it will not ignite or burn. Most units leak around the condenser which is where the highest refrigerant pressures are and the condensors are outside where any leaking propane propane will be disbursed by wind and solar heating. You are welcome to disagree with my statements but please find a better technical source of support for your arguments than a tort lawyer publication.