Abstract: A duct fan (1) has a centrifugal fan with a motor (10) and a centrifugal impeller (11). A housing has an intake shell (2) on an intake side, that defines an intake portion (52), and accommodates the centrifugal impeller (11). The housing also has an exhaust shell (3) on an exhaust side that defines an exhaust portion (53). A bowl-shaped motor mount (5) is arranged in the exhaust shell (3). A continuous flow channel (20) to the exhaust portion (53) is formed between the motor mount (5) and the exhaust shell (3). A flow (S) generated by the centrifugal impeller (11), during operation, is guided by the flow channel (20).

Abstract: A filter cartridge for cleaning air includes a perforated sheet metal outer cage having a cylindrical shape, the diameter thereof being the same over the entire length of the filter cartridge, a base disc closing off the lower end of the filter cartridge, and an inlet fitting closing off the upper end. The filter cartridge includes a conical perforated sheet metal inner cage extending from the base disc to the inlet fitting in the interior of the perforated sheet metal outer cage. The perforated sheet metal inner cage tapers down conically in the direction from the base disc to the inlet fitting, wherein the diameter of the perforated sheet metal inner cage decreases from the base disc to the inlet fitting. The filter cartridge further includes an activated carbon layer disposed in the intermediate space between the perforated sheet metal inner cage and the perforated sheet metal outer cage.