HCFC-22, commonly called R-22, has been a common refrigerant used in residential heat pumps and air conditioners for more than 40 years. But releases of R-22, such as those from leaks, contribute to ozone depletion, and the making of R-22 results in a byproduct that contributes to global warming. This refrigerant is now being phased out by the EPA. By January 2020, chemical manufacturers will no longer be able to produce R-22.