Abstract: An adjustable duct assembly for the collection of fumes, dust and the like comprises two duct sections pivotally connected end to end and to a base by an external duct support system. The duct sections are retained in a selected position without the need for any friction fittings by a combination of a counterbalance arm extending from the duct support of a lower or outer duct section beyond the pivot point of the elongate arms, to counterbalance the lower or outer arms, and a retraction or tension-applying arm which holds the inner duct section in position.

Abstract: An adjustable duct assembly for the collection of fumes, dust and the like comprises two duct sections connected end to end by a duct support system comprising two elongate arms pivotally connected, the arms attached to the adjacent ends of the ducts, externally. A counterbalance arm extends from the duct support of a lower or outer duct section beyond the pivot point of the elongate arms, to counterbalance the lower or outer arms. A filter arrangement may be associated with the duct assembly, consisting of a generally planar filter element within a housing. A travelling nozzle arrangement directs a stream of air in a direction countervailing the normal flow through the filter, for backwash cleaning of the filter. First and second drives propel the nozzle simultaneously across and along the filter, to provide full backwash cleaning coverage of the filter.