PURPOSE: To prevent the sucking-in of air at the time of an adverse wind, by fixing an air stabilizing vane having an extended top to an upper portion of an L-shaped exhaust pipe which is disposed in a freely rotatable manner.

CONSTITUTION: An air stabilizing vane 2 having an extended top is fixed to an upper portion of an L-shaped pipe 1 at its side portion, in the manner that it is extended toward an opening perpendicularly from the axis of the pipe 1. Further, an annular metal ring having vibration-damping projections 6 is fitted tightly to an upper portion of an inner pipe 5, while an annular metal ring 8 having vibration-damping projections 6 and pipe suporting projections 7 is fixed to a lower portion of the inner pipe 5 at a prescribed position. A proper gap is provided between the vibration-damping projections 6 and the L-shaped pipe so that the pipe can be turned slowly. Thus, since the air stabilizing vane is turned by a light wind, it is enabled to ventilate air with ease.