APPARATUS FOR CONTROLLING THE VENTILATION OF LABORATORY FUME HOODS

摘要

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 moveable 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.