HCFC (R-22) Freon will be a serviceable refrigerant until 2014.

Currently Great lakes manufactures dual refrigerant compressed air dryers. Units charged with R-22 are capable of direct replacement with R-407C. Great Lakes currently utalizes R-22 due to the singificent cost factor. R-400 series refrigerants are two to three times the cost of R-22. As the planned phase out of R-22 until 2020 raises the cost of R-22 Great Lakes will convert to R407C as the initial refrigerant charge. We feel it is best to enjoy the cost savings and produce a more economical dryer until the market prices forces a change.

For more specific information a link is provided to the EPA

http://www.epa.gov/ozone/title6/phaseout/hcfc.html