Integral Unit (Integrated Unit):

This type of refrigerated container has an integral refrigeration unit for controlling the temperature inside the container. The refrigeration unit is arranged in such a way that the external dimensions of the container meet ISO standards and thus fit into the container ship cell guides, for example. The presence of an integral refrigeration unit entails a loss of internal volume and payload.

 When being transported by ship, integral units have to be connected to the on-board power supply system. The number of refrigerated containers which may be connected depends on the capacity of the ship's power supply system. If the aforesaid capacity is too low for the refrigerated containers to be transported, "power packs" may be used, which are equipped with relatively large diesel generators and satisfy ISO requirements with regard to the dimensions of a 20' container. When at the terminal, the containers are connected to the terminal's power supply system. For transport by road and rail, most integral unit refrigeration units are operated by diesel generator. This may either be a component of the refrigeration unit or connected to the refrigeration unit as a "clip-on unit".

 Air flows through the container from bottom to top. In general, the "warm" air is drawn off from the inside of the container, cooled in the refrigeration unit and then blown back in the container as cold air

To ensure adequate circulation of the cold air, the floor is provided with gratings. Pallets form an additional space between container floor and cargo, so also forming a satisfactory air flow channel. In addition, the side walls of the container are "corrugated", which ensures satisfactory air flow there too.

In the upper area of the container, adequate space (at least 12 cm) must likewise be provided for air flow. For this purpose, during packing of the container adequate free space must be left above the cargo. The maximum load height is marked on the side walls.