PURPOSE: To efficiently discharge contaminated air without diffusing by disposing a vortex flow-generating guide blade at a suction side of a blower fan.

CONSTITUTION: An exhaust hole 14 is provided at a ceiling 13 above a contaminated air generating place 12 near a floor 11. An axial flow blower fan 15 is disposed in the hole 14, and vortex flow-generating guide blades 16 are disposed at the suction side, i.e., the lower side of the fan 15. The blades 16 are twisted at a certain angle to the flow of the air to be sucked to the fan 15, and a thickness of a generated vortex is controlled by regulating the angle. The vortex S is generated immediately at the lower side of the fan 15 by the blades 16 to reach the floor 11. Accordingly, the contaminated air can be efficiently discharged without diffusing, and since the vortex flow is generated, it does not need occupy a space between the ceiling and the floor.