Modular nesting metal conduit, in particular for discharging fumes

A double walled interfitting modular duct for a chimney, the duct having interconnected elements, each of the interconnecting elements comprising an outer duct and an inner duct, the outer and inner ducts each having a male end and a female end, wherein the male and female ends alternate within each element, each said female end of the inner and outer duct elements being dimensioned and structured for engaging the corresponding male end of an adjacent corresponding inner and outer duct element at any selected point along a length of the male end, wherein the female end of each said inner duct element includes a first gasket having a lip, and a chamber formed adjacent to the lip of the first gasket, the first gasket and chamber of the female end being engageable over the male end of the inner duct of an adjacent element, whereby the male end can be cut to adapt a length of the duct to an available space by engaging the female end at the selected point, two inner and outer duct elements being assembled together via a second annular gasket attached to an axial end of a duct element having a female end on the inner duct and a male end on the outer duct, the second annular gasket being located between the inner duct between the inner and outer duct elements.