Abstract: A safety element is disclosed for influencing or inspecting fluid media in a duct, in particular a double-walled safety duct whose walls are separated by a hollow space. The safety element has a housing formed by walls and flanges for sealingly connecting it to the duct. The housing is surrounded on all sides by a second wall (6) separated from the first wall (5) by a hollow space (7) which is closed in a gas-tight manner and can be connected with measurement equipment for inspecting its contents. The hollow space (7) communicates through one or several bores (13) with a groove (15) shaped around the duct into the sealing surface (14) of the flange (1) or its seal (18).