A gas-tight sealing device (10) encloses at least one part of a coupling element (12) as well as at least one section of a line element (14) connected to the coupling element (12). The the gas-tight sealing device (10) comprises a sealing device portion or wall (11) that adjoins a first sealing point and a second sealing point (16, 18). The sealing device portion or wall (11) extends around, in a gas-tight manner, the line element (14) and the coupling element (12) or a wall (20), or a further line element, in or at which the coupling element (12). The gas-tight sealing device (10) encloses a volume defined by the geometry of the sealing device portion (11) in a gas-tight manner between the first sealing point (16) and the second sealing point (16, 18).