Abstract: Apparatus for degassing a liquid fluid, the apparatus being installed inside an envelope (1) which contains a supply (20) of said degassed fluid in the liquid state in the bottom thereof and in equilibrium with its saturated vapor, the apparatus comprising perforated trays (2, 3, 4) situated above the level of the supply and fed with liquid fluid to be degassed, said trays dispersing the liquid and feeding a tank (7) which includes at least one pipe (8) extending therealong in the vicinity of one of its walls (12) and supplied with vapor of said fluid at a pressure P1 which is greater than the pressure P within said envelope, said pipe including a perforated zone (14) running along its entire length inside the tank and on its side adjacent to said wall, said perforated zone serving to fill the bottom portion of the pipe cross-section with liquid from the tank allowing the vapor to escape from said pipe, the apparatus including the improvement whereby said tank is closed (18) betweeen said wall and said pipe,