A gas-selection device for a sealed storage container with modified or controlled atmosphere, remarkable in that it includes a hollow body and at least one first orifice, a second orifice and a first membrane, said first and second orifices connecting the inside of said body to the outside, said first membrane being disposed inside said body between said first and second orifices so that the gases flowing from the first orifice to the second orifice, or vice versa, necessarily and solely pass through said first membrane, and in that the device is arranged so as to be secured sealingly to one of the walls of the container, so as to allow a flow of gas from its second orifice through the wall, or vice versa.
