The ozone layer absorbs the sun’s ultraviolet radiation. In the 1980s it was understood that chlorine-containing CFC (R12, R11) and HCFC (R22) refrigerants break down ozone in the atmosphere; the Montreal Protocol (1987) phased these gases out. ODP measures this effect of a refrigerant taking R11 = 1: 1 for R12, 0.055 for R22, and 0 for R404A and all later HFCs, HFOs and natural refrigerants.
Systems using R22 are still in the field in Turkey; new production and import of R22 is banned, and servicing is possible only with reclaimed gas. These systems are converted to zero-ODP refrigerants such as R407C and R448A/R449A with a compressor and oil change; the expansion valve and seals are reviewed.
ODP and GWP measure different things: R22 has a low ODP but a GWP of 1,810; R404A has an ODP of zero but a GWP of 3,922. Because today’s regulations have largely solved the ozone problem, they now focus on GWP. Our refrigerant pages give the type, safety class and GWP of every refrigerant.