Abstract: The valve, mounted on a vent pipe, allows the passage of gas in both directions, but prevents any escape of liquid fuel. The valve comprises a closed containment 7 equipped with a lower inlet port 8 and with an upper outlet port 9 which are connected to the vent pipe, a stationary circular inner cup 10 kept spaced from the inner wall of the containment and from the inlet port, a vertically displaceable assembly surmounting the cup and comprising a float 13 and a needle 16 which is equipped with a gasket 17 and is fixed to the float and which, in the high position of the assembly, can close off the outlet port 9, and means 11, 14, 15 for causing an upward displacement of the assembly as a result of an inclination of the containment 7. Furthermore, the annular space between the cup 10 and the inner wall of the containment 7 is profiled so as to form a Venturi tube 18 which is kept in relationship via at least one passage 20 with the volume 19 located between the cup 10 and the base of the float 13.