I advocate hydrocarbon refrigerants for vapor compression systems whether it’s refrigerators, dehumidifiers, split systems, whatever. There are a lot of advantages to them over proprietary cocktails like R-134a, R-22, 410a and so on. First of all, they are naturally found on this planet with the help of a little refinement. Propane, Butane, Isobutane, Propylene are simple hydrocarbon chains with pretty good thermal properties. These natural refrigerants don’t contain any nasty fluorine, break down quickly in the atmosphere and are non toxic, more or less. Enough of them in a confined space will asphyxiate a person, but that is true of any gas that isn’t oxygen I think. Oh yeah, only problem is mix hydrocarbon refrigerants with the right amount of oxygen and you got yourself a freaking bomb.
No doubt people have been killed or severely hurt by these gases under certain circumstances. Fortunately, at least with propane (I’m not sure about the rest), there is a very specific ratio of HC gas to oxygen to get an explosive mixture. These conditions don’t normally exist within a vapor compression system. I sure hope not! So long a vapor compression system remains leak free, I see no danger in using these volatile gases for refrigerants. Even if there were some sort of catastrophic failure inside the system that caused a spark, there would be no ignition. If there were a small leak in a system, it is unlikely enough propane would leak in quantities sufficient to get an explosive mixture. My only concerns with using propane as a refrigerant or any hydrocarbon would be in a case where large amounts of it escaped from a system in a short time. These HC refrigerants are being used extensively in Europe and in the SE Asia/Pacific region I think, for refrigerators, air conditioners, dehumidifiers, commercial refrigerators and freezers in grocery stores and so on. To my knowledge, there haven’t been problems warranting the return to proprietary refrigerants. These machines of course, have been thoroughly tested and “put through their paces”. The manufacturing processes, servicing, repair, disposal and the like have been thought out and made to be safe. So, I should think people would feel as safe about having a pound of flammable refrigerant in the various appliances in their homes, as they feel about having flammable natural gas piped in or 240 VAC coursing through the walls. These potentials have been “tamed” so to speak such that they are made safe with the knowledge and respect of their potential dangers.
On the other hand is the experimental hobbyist. I’ve used BBQ grade (consumer grade) propane in modified/homemade refrigeration systems. Quite successfully I might add. I immediately saw it’s advantage, or at least a cleaner, more refined version called R-290, and I felt that HC refrigerants were the way to go. Obviously, I’m not ignorant of the potential dangers of handling a flammable vapor/liquid, but when I read hostile opinions from industry technicians (mostly Americans I think) about HC refrigerants; I usually chock it up to fear of change and protecting the status quo and the domination of refrigerant manufacture by companies like Dupont or Dow Chemical. Handling any compressed gas is dangerous and requires some respect and common sense.
As a refrigeration hobbyist, there are always unforeseen outcomes when testing an idea out. Even though I advocate HC refrigerants, I have to say remaining humble about my brazing abilities and knowledge of material science, I’m still a little nervous about a possible catastrophic leak in a machine I build. It was recently brought to my attention by another hobbyist how dangerous and unethical it is to run untested refrigeration equipment with flammable gases under the same roof of unsuspecting neighbors. He is absolutely correct, it is. It is one thing if you live alone or have a safe place to test such things, but for me, I’ll stick to the proprietary refrigerants for now.
R-134a is toxic, proprietary, more expensive than propane, but it won’t explode when mixed with oxygen. An awful lot of the stuff would have to be vented to cause anyone harm. Another advantage of R-134a is that there is a ton of literature on the stuff with all of the thermophysical properties well documented. BBQ propane on the other hand, is a different blend of gases in each and every bottle. R-290 would be well documented, but is probably as expensive if not more than R-134a and I bet quite hard to get here in the states. R-134a can be reused and recycled and it’s global warming potential is non-issue if handled responsibly and recovered correctly (not considering it’s original manufacture which is probably quite damaging to the atmosphere).
I think I will get a hold of a bottle of R-134a or other nonflammable refrigerant for the purposes of experimentation and testing. In the future, I build something in a more standardized fashion and can prove the relative safety of HC refrigerants in it, then I will take the steps to implement them.
M.C. Pletcher
musings on entropy 
Questions or Comments?