Ammonia was one of the early chemicals used in household refrigeration that was eliminated because of health and safety issues. We went to safe CFC's around the 1930's, but that was destroying the ozone layer. So, the Montreal Protocol of 1990 had us all switch to HFC's.
But, now, the Obama Administration is pushing to replace HFC's with "natural" chemicals including ammonia!
Here is OSHA's hazard write-up for ammonia in the workplace:
More... Ammonia is considered a high health hazard because it is corrosive to the skin, eyes, and lungs. Exposure to 300 ppm is immediately dangerous to life and health. Ammonia is also flammable at concentrations of approximately 15% to 28% by volume in air. When mixed with lubricating oils, its flammable concentration range is increased. It can explode if released in an enclosed space with a source of ignition present, or if a vessel containing anhydrous ammonia is exposed to fire. Fortunately, ammonia has a low odor threshold (20 ppm), so most people will seek relief at much lower concentrations.
This change is being done in the name of "global warming." I suppose HAZMAT labels on the fridge door will be required. Is this crazy, or what!?