Abstract: A fire barrier aeration device intended to ensure free exchange of air between two spaces separated by a wall which is equipped therewith and to break the passage of gas through the wall, when fire breaks out in one of the spaces, comprises at least one body (10) made of a refractory material intended to be disposed in an orifice of the wall. The body is passed through by an aeration passage (17) at the end of which, emerging on a face of the body which is turned in the direction from where the fire may come, there is disposed an element (21) made of an intumescent material which in the absence of fire leaves a portion of the cross section of the aeration passage (17) free and which is at least partially surrounded by a flexible material (22) for guiding and confining the inflation of the intumescent material (21) in the aeration passage (17) in order to make the material completely block the passage in the case of fire.