A device for controlling the composition inside a shipping/storage container for produce, such as bananas, is disclosed. Such atmospheric control is particularly important when dealing with the ripening of respiring fruit. The device comprises a chamber surrounded by an outer wall, at least a portion of that wall made up of a selectively gas-permeable membrane which is in communication with the outside atmosphere. The chamber also includes at least two channels which are connected to the container: one which transmits gas form the chamber to the container, and one which transmits gas from the container to the chamber.