A duct joining system for providing an air-tight seal and mechanical connection for ducts and fittings is disclosed. The duct joining system includes a flexible gasket that provides the seal and mechanical connection between a first duct and a second duct. The flexible gasket is, e.g., mounted on a male end and is affixed at an angle relative to normal of the male end of the duct. The female end of the other duct includes a raised bead in which the flexible gasket is seated when the ducts are properly joined. The angled flexible gasket seated in the raised bead forms an air-tight seal as well as fastens or locks the male end to the female end. If desired, the flexible gasket may be mounted in the female end and is seated in a depressed bead in the male end when properly joined. Alternatively, when a flexible duct is used, a clamp may be clamped over the female end of the flexible duct and over the male end of a fitting to provide an air tight seal and fastened connection.
 This invention was made with Government support under contract number DE-FG03-76SF00098 awarded by the United States Department of Energy and CRADA BG-97-352-01. The Government has certain rights in this invention.