Abstract: The invention relates to seal means (I, TR) for sealing two substantially flat closing surfaces (9a,7a), respectively of two separable elements (9,7), for forming a boundary between a first space (101) and a second space (102), in order to prevent a first gas flow (&PHgr;1) propagating in the first space to exit through an interface (I) between said two closing surfaces disposed one opposite to the other for sealing, comprising the construction of a set of troughs (TR) in at least one of the closing surfaces (9), carried out throughout the length (L) of said boundary in the direction of said first flow, and comprising a counter-flow (&PHgr;2), propagating from the second space (102) through said troughs, which have construction parameters including a width (w), a depth (h) and a separating width (W), determined in combination with the height (H) of the interface (I) and said length (L) of the boundary, for preventing the first flow (&PHgr;1) to exit through the interface (I) along the troughs (TR) and along t