Abstract: Fume hood controller apparatus includes a computing means, together with associated memory, which can be configured for horizontally and/or vertically moveable sash doors by inputting the necessary dimensions of the sash doors and other structural features, such as the upper lip height, frame widths and the like. The apparatus rapidly calculates the size of the uncovered area of the fume hood as a functions of the position of the sash doors.

Abstract: Apparatus for controlling the air flow through a fume hood to maintain a predetermined average face velocity through an uncovered portion of an opening of a fume hood of the type which has at least one movable sash door adapted to cover the opening as the fume hood sash door is moved. The apparatus detects the position of each moveable sash door and calculates the size of the uncovered portion of the opening, measures the actual flow of air through the exhaust duct, and varies the flow of air through the exhaust duct responsive to door position signals and the actual flow signal for controlling a flow modulating means to maintain the predetermined average face velocity through the uncovered portion of the opening.