Abstract: A media storage container has a body portion, a lid, and an injection valve which enables the injection of a protective atmosphere into the interior of the container from outside the container. A vent enables the escape of atmosphere from within the container when the protective atmosphere is injected into the container at a pressure higher than the ambient atmosphere outside the container. Co-acting first formations on the body portion and lid constitute a cam closure mechanism in which, in a first position, the lid is a loose, unsealed fit on the body portion enabling venting of the container while continuing to inject protective atmosphere to allow the inside of the container to be purged, and in a second position the camming action of the closure mechanism seals the lid to the body portion to enable the cavity to be pressurized.