Abstract: The object of the invention is a container cover (5) to close a filling opening (4) in a transport and/or storage container, in particular a temporary and/or permanent storage container for contaminated and/or activated substances, with at least two grooves (9) on the inside of the container cover (5) that are arranged at an interval to one another, with at least two gaskets (8) each arranged in a groove (9), and with a bypass device (18) to circulate (19) a gas, the bypass device (18) being connected with at least one groove (9) in such a way that an undefined gas volume (17) confined by the gasket (8) and the groove (9) can escape through the bypass device (18).