R-408A is classified as an HCFC refrigerant and has a low ozone depletion potential. It is a blend of R-22, an HCFC, and HFC refrigerants R-125 and R-143a. It has been blended to closely match the physical and refrigeration properties of R-502. The purpose of 408A was to serve as an interim drop-in replacement for low and medium temperature commercial R-502 units.
R-502 is a CFC refrigerant and was phased out in the 1990’s due to the Montreal Protocol agreement. Since R-408A is an HCFC refrigerant it contains Chlorine just like R-502 and has been phased out as well.