A line penetration for routing a line through a passage opening of a building part that includes a first and a second building-part wall, between which an intermediate space is provided. The line penetration has a closure element that includes: an inner part for filling the intermediate space in the region of the passage opening; holding parts, with cross section smaller than that of the inner part, disposed on both sides of the inner part; a straight-through line opening, which penetrates the inner part and the holding parts in the direction in which they are disposed; and a sliding device, which is formed in order to guide the line slidingly and gas-tightly through the line opening.