Abstract: A self-contained detachable refrigeration unit is disclosed for use in a cargo-carrying container having at least one porthole therein. Refrigeration units are well known for keeping cargos at low temperatures. In many cases such units rely on outside power. Alternatively, they include an internal combustion engine which is noisy and in turn produces a disturbance in the location of the container. The present unit is completely self-contained and overcomes the problems of the prior art. It provides an assembly having a detachable means for mounting on the container adjacent the porthole, an insulated tank supported within the frame assembly, the tank adapted to contain liquid carbon dioxide. The assembly also includes a control panel with a temperature selective control means for controlling the flow of liquid carbon dioxide to the container. A porthole closure assembly is connected to the frame assembly by a flexible connector.