A filter-fan unit has a housing, at least one fan arranged in the housing, and at least one filter connected to the housing. The housing is transferable from a transport/storage position into a position of use, wherein the transport/storage position is significantly smaller than the position of use. The housing is foldable from the transport/storage position into the position of use. The housing has a housing frame and one or more sidewalls connected with one side to the housing frame.