PURPOSE: To make possible automatic cleaning of a vane smudged with soot, by spraying washing water against smoke or oil in the air, thereafter making the vane for separation by impingement movable.

CONSTITUTION: Air carrying smoke or oil sucked by a fan 7 goes into a suction duct 5 to be washed by a curtain of washing water 18 flowing down from nozzles 36. Then the air and smoke impinges upon the surfaces of vanes 12, whereupon remaining oil or dust attaches to the surface of the vanes 12 to be removed. And the washed air is discharged from a discharge duct 6. The vanes 12 are attached to an endless chain supported movably by an upper and a lower pulleys 8, 10. Consequently, when the fan 7 is out of operation, by moving the vanes 12 through a washing tank 17, automatic cleaning thereof can be conducted.