These substances have been used in place of Freon®-11 and -12, which were commonly used to blow foam rubber and in refrigeration, respectively. These substitutes work to reduce the depletion of ozone by either:

• having a chemical structure that reacts with tropospheric gases, so that they do not survive long enough to diffuse into the stratosphere and into the ozone layer (HCFC-22 has that extra hydrogen atom, which allows the HCFC to react with OH and breakdown into other substances while still in the troposphere);
• not containing chlorine at all (HFC-134a, an effective substitute for Freon®-12 in refrigeration, is hydrogen/fluorine/carbon, but no chlorine).

Freon®-12 has been banned just about everywhere either by the Montreal Protocol or individual regulations in countries. It is now about as inexpensive to use HFC-134a as it was to use Freon®-12 when it was in vogue (currently, F-12 is so expensive that it is not cost effective to recharge old refrigeration units with F-12).