A container having a plurality of walls, and at least one inlet and/or outlet, said container including an apparatus for controlling the composition of gases within the container, the apparatus including at least one sensor, at least one controller and at least one gas permeable membrane, through which membrane different gases can pass at different rates, said membrane dividing the container into a first region being for holding cargo and a second region defining a gas buffer region, and said membrane being permeable permitting for nitrogen, oxygen and carbon dioxide at different flow rates, wherein the buffer region is in communication with the ambient atmosphere through one or more vacuum pump(s).
