Abstract: The invention provides a gas venting means for venting gases evolved by a liquid (2) enclosed inside a container (1). The means comprises a flexible tube (4) having a first end (5) venting to the exterior of the container (1) and a second end (10) extending into the container, the second end venting into the interior of the container through a semipermeable membrane (11). Preferably, the flexible tube (4) is provided with buoyancy elements near the second end (10) so that the semipermeable membrane is always exposed to the air space above the liquid in the container.