A refrigerant for a cooling device comprising a cooling circuit with at least one heat exchanger, the refrigerant undergoing a phase transition in the heat exchanger, the refrigerant being a refrigerant mixture composed of a mass fraction of carbon dioxide (CO2), a mass fraction of pentafluoroethane (C2HF5) and a mass fraction of at least one other component, wherein the mass fraction of carbon dioxide in the refrigerant mixture is up to 60 mass percent, the mass fraction of pentafluoroethane being 11 to 72 mass percent, the other component being 2,3,3,3-tetrafluoropropene (C3H2F4), the mass fraction of 2,3,3,3-tetrafluoropropene being up to 51 mass percent.