Abstract: A high efficiency air filter for use in a standard return air grille is provided. Standard return air grilles possess filter receptacles for accepting air filters, a closeable cover with a cover flange for engaging air filters and a duct interface that leads away from the air grille to the remainder of the return air ducts. The air filter has a filter flange with a gasket that is sized to fit within the filter receptacle of the air grille, such that when the cover is closed, the cover flange seals against the cover and the filter receptacle. The gasket is affixed to a housing that is sized to extend beyond the filter receptacle into the duct extending beyond the return air grille. An extended pleat air filter is contained within and sealed to the walls of the housing such that air passing through the return air grille substantially passes through the air filter prior to entering the remainder of the return air duct.

Abstract: A vacuum excavation system is provided in which a vacuum is generated for withdrawing dirt, water or other material from a vacuum excavation site, and whereby such material is delivered to a containment structure, preferably of the hopper type having a discharge. A valve is provided for the vacuum, such that actuation of the valve interrupts the vacuum, whereby material pickup may be discontinued and/or material may be discharged from the containment structure. Preferably the vacuum-controlling valve exists in a conduit between the situs of vacuum generation and a containment structure. The valve will preferably be controlled by a pneumatic/electrical control for operation of the same.The excavation system is preferably vehicle-mounted, with the same motor that drives the vehicle also driving an air compressor for operating a pneumatic tool as well as driving the vacuum generator.