Abstract: A method and apparatus for controlling the temperatures of cargo in a container, wherein cooling air is circulated over and beneath the cargo, then between the cargo and the door(s) of the container, for subsequent passage towards the front of the container over the top of the cargo, wherein the cooling air at the rear of the container is separated into two streams by an air separator board having a first limb which is located over the top of the cargo, and a second limb extending approximately at right angles to the first limb so that the internal stream at the rear of the container is separated from the external stream which is subjected to warming from ambient air around the container. The invention also extends to an air separator board per se, which is L-shaped, and preferably made of wood and has ribs on its internal and external faces.