NOVELTY - A non-combustible mixed refrigerant comprises 1st group material e.g. nitrogen, argon, and/or methane, 2nd group material e.g. tetrafluoromethane, 3rd group material e.g. trifluolomethane, hexafluoroethane, ethane, ethene and/or monofluoromethane, 4th group material e.g. perfluoropropane, pentafluoroethane, trifluoroethane, propane, propylene, iodotrifluoromethane, 1,1,2,2-tetrafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1-difluoroethane, and/or hetrafluoropropylene, and 5th group material e.g. 1,3,3,3-tetrafluoropropylene, 1,1,1,2,2-pentafluoropropane, and/or 1,1,1,2,3,3,3-heptafluoropropane.    USE - A non-combustible mixed refrigerant for cooling devices.    ADVANTAGE - The non-combustible mixed refrigerant exhibits high efficiency and is environmentally friendly.    DETAILED DESCRIPTION - A non-combustible mixed refrigerant comprises 1st group material e.g. nitrogen, argon, and/or methane, 2nd group material e.g. tetrafluoromethane, 3rd group material e.g. trifluolomethane, hexafluoroethane, ethane, ethene and/or monofluoromethane, 4th group material e.g. perfluoropropane, pentafluoroethane, trifluoroethane, propane, propylene, iodotrifluoromethane, 1,1,2,2-tetrafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1-difluoroethane, and/or hetrafluoropropylene, and 5th group material e.g. 1,3,3,3-tetrafluoropropylene, 1,1,1,2,2-pentafluoropropane, 1,1,1,2,3,3,3-heptafluoropropane, perfuorobutane, 1,1,1,3,3, 3-hexafluoropropane, 1,1,2,2-tetrafluoropropane, trifluoroethane, 1,1,1,2,3,3-hexafluoropropane, 1,1,1,3,3-pentafluoropropane, 1,1,1,2,2,3,3,4,4-nonafluorobutane, 1,1,1,2,2,3,3-heptafluoroprobutane, 1,1,1,2,2,4,4,4-octafluorobutane, 1,1,1,2,3-pentafluoropropane, 1,1,2,2,3-pentafluoropropane, 1,1,1,2,3,4,4,4-octafluorobutane, and/or 1,1,1,2,2,3,3,4-octafluorobutane. Total molar concentration of each group of material in mixture containing 5 groups is 100%. Molar concentration of 1st group material is 5-35%. Molar concentration of 2nd group material is 10-40%. Molar concentration of 3rd group material is 10-30%. Molar concentration of 4th group material is 5-20%. Molar concentration of 5th group material is 10-25%. Non-combustible mixed refrigerant can be utilized at cryogenic temperature of -90-140 degrees C.