Air separators are used in a wide variety of working areas. These include, among others, alternative fuel production, waste processing, the timber industry, etc. The air separator acts as a safety measure during the subsequent re-shredding of the input material in this way, high costs for replacement and wearing parts for re-shredding can be avoided. Moreover, the quality of the fuels is optimized by using the air separator. The separation of the materials in the air separator is achieved by an uniform and single-layered homogeneous distribution of the input material, which is fed into the separating drum of the air separator across the entire belt width of the air separator. Heavy materials and critical foreign objects are separated from the light materials by means of air injection. The light materials are transported by means of a high-speed airflow into the expansion chamber, where the air speed is reduced to such a degree that the light materials can be transported on a subsequent belt conveyor to the following processing stage. The injected air is removed again in the upper section of the air separator and, depending on the application, is sucked in again by the fan or fed into a filter unit. In order to obtain high-quality recycling raw materials, an air separator with three fractions is used to achieve higher separation quality.