PURPOSE: To automatically shift an air passage to a blow-off port connected to a heater without operating the heater.

CONSTITUTION: A rectifying divider 13 is provided at the blow-off ports 5, 6 of a blower casing. The central part of the rectifying divider 13 projects inward. A pair of control ports 17, 18 are provided in a side wall facing the rectifying divider 13 and are placed downstream from such a position that the cross-sectional area of the blow-off ports of the blower casing is minimum. Completely fluid elements are integrated with the blower casing. When the heat catcher 7 is connected to one blow-off port 6, a pressure difference is made in the cross-sectional direction of the flow and air is thereby oriented toward the blow-off port 6.