Refrigerants such as ammonia are used for low-temperature systems. These include food and process cooling, ice rinks, and so forth. Propane has been used for some special applications. Now that chlorinated hydrocarbons have been determined to be harmful to the earth’s ozone layer, R-11 (CCl3F), R-12 (CCl2F2), and other similar compounds that were in common use along with the less harmful R-22 (CHClF2) have had much attention in the press. Recent international protocols (standards) have set schedules for the elimination of damaging refrigerants from commercial use.
Replacements have been, and are being, developed. Part of the challenge is technical and part is economic. First, to find a fluid that has optimal characteristics and is safe is a challenge. Second, to encourage manufacture to produce and distribute the fluid at an affordable price and in sufficient quantities is another. R-123 (CHCl2CF3) has been developed as a near-equivalent replacement for R-11, with R-134a (CH2FCF3) replacing R-12. R-123 still comes under criticism for having some chlorine in it. R-134a can be bought at auto supplies stores for automobile air conditioners. Most new cars are required to have R-134a in their air-conditioning systems.
R-22 is used widely in residential and commercial air-conditioning scroll compressor systems. It too will be phased out someday (probably during the period 2020–2030). However, finding a suitable, widely accepted replacement has not come as quickly as first thought.