The disclosure relates to an apparatus for reducing the quantity of solid particles in ambient air. A predefined treatment area is delimited at least in part by an enclosure. The enclosure is at least partially non-physical and formed by at least one air curtain that can be produced by an air flow generating device. At least one air filter device, which is connected in terms of flow to the ambient air of the treatment area is designed to filter solid particles directly out of the ambient air of the treatment area.