The blower has inner chamber for the blades (1) divided by a separating wall (12) into two individual chambers (13,14). One chamber is connected to the inlet opening (15), and the other chamber is connected to the chamber (4) outside of the blades. The separating wall extends from the sidewall opposite the open side of the blade into the inside of the blade. The separating wall is located such that one side faces the small diameter region of the spiralled outer wall (8), and the other side of the larger diameter region.
