Abstract: A radial blower for producing an air stream which is supplied as a secondary air to a waste gas stream of an internal combustion engine has a spiral housing having a substantially tangentially oriented blower output and accommodating a blower wheel which rotates in the spiral housing about a rotary axis in a rotary plane. The blower output forms with the rotary plane of the blower wheel an acute angle which converges in a flow direction of air. An air guiding chamber is provided with stationary guiding elements, and the blower output is open in the air guiding chamber. An overflow opening extends substantially radially to the rotary axis of the blower wheel. The guiding elements of the guiding chamber deviate an inflowing air substantially radially to the overflow opening. A second spiral housing accommodates a second blower wheel. The overflow opening opens in the central region of the second spiral housing.