Product review (3 stars): Just the facts
R-22a (a clever name given to what is actually R290 or propane), will work quite well in pure form or mixed with remaining real R-22. It can even improve overall system performance and subsequent efficiency. Using propane as a refrigerant is not new, it has been done safely for many years. However, it is still propane and as such is very flammable and or explosive. If you put this in a leaky system it could easily fill an enclosed area within your home.  Just as a natural gas leak in your home could be dangerous so could R290 propane (or R-22A as it is referred to here). I know of no law that precludes you from using this in your system but you should be advised that if your system experiences a problem that results in someone being hurt you are leaving yourself open to prosecution. This is especially true if the injured person is a qualified service technician who wasn't told that you had put propane in your system.