An air passage with - a housing, - a connecting piece for connection to an air distribution system, - an internal space delimited by the housing, and - an air outlet cross-section, wherein the housing has an air outlet region in the form of a truncated pyramid, in which walls of the housing form an angle of between 5° and 20° with a plane formed by the air outlet cross-section, wherein the air outlet region is separated from the remaining internal space by a first air passage cross-section formed by a cover surface of the air outlet region, wherein a base surface of the air outlet region and the first air passage cross-section of the air outlet region are rectangular, wherein a rectangular air guiding element is arranged between the first air passage cross-section and the air outlet cross-section, wherein the air guiding element - is plate-shaped, - defines a plane parallel to the air outlet cross-section and - has a multiplicity of perforations which together form a second air passage cross-section, wherein a free space is present which extends circumferentially around the air guide element between an outer edge of the air guiding element and the walls of the housing and which forms a third air passage cross-section, characterized in that a proportion of a free area, which defines the second air passage cross-section, is between 5% and 20%, preferably between 7% and 15%, of a total area of the air guiding element, so that a large part of a supply air volume can be guided through the third air passage cross-section in the course of the flow flowing through the air outlet region. - a housing, - a connecting piece for connection to an air distribution system, - an internal space delimited by the housing, and - an air outlet cross-section, wherein the housing has an air outlet region in the form of a truncated pyramid, in which walls of the housing form an angle of between 5° and 20° with a plane formed by the air outlet cross-section, wherein the air outlet region is separated from the remaining internal space by a first air passage cross-section formed by a cover surface of the air outlet region, wherein a base surface of the air outlet region and the first air passage cross-section of the air outlet region are rectangular, wherein a rectangular air guiding element is arranged between the first air passage cross-section and the air outlet cross-section, wherein the air guiding element wherein the housing has an air outlet region in the form of a truncated pyramid, in which walls of the housing form an angle of between 5° and 20° with a plane formed by the air outlet cross-section, wherein the air outlet region is separated from the remaining internal space by a first air passage cross-section formed by a cover surface of the air outlet region, wherein a base surface of the air outlet region and the first air passage cross-section of the air outlet region are rectangular, wherein a rectangular air guiding element is arranged between the first air passage cross-section and the air outlet cross-section, wherein the air guiding element - is plate-shaped, - defines a plane parallel to the air outlet cross-section and - has a multiplicity of perforations which together form a second air passage cross-section,