The invention relates to a small, low-noise side channel compressor for producing a defined volumetric flow, such as is needed in particular for devices for ventilation therapy. This is achieved by means of a new type of shape of the blade chambers (24) in the impeller (12) and the blade chamber walls (29), which separate the blade chambers and become thicker toward the circumference of the impeller, supported by a high-speed drive and a large number of blade chambers (24) at a small impeller diameter.