Abstract: A vacuum cleaner has a casing with an internal duct connecting the air outlet of the vacuum cleaner fan with a discharge aperture. The casing has one or more primary apertures formed in its wall and communicating through the interior of the casing with one or more secondary apertures in the duct wall, whereby the air flow through the duct induces a secondary flow of ambient air through the primary apertures. This secondary air flow effects a cooling of the casing wall and a reduction of the temperature of the discharged air. An apertured internal partition may be provided for locally reducing the cross-section of the coolant air flow path, thereby insuring a uniform cooling effect upon the casing wall.