Abstract: A system for maintaining a desired pressure (either positive or negative with respect to surrounding) in a sealed room or other substantially sealed closed space has a gas supply and a gas exhaust connected to the space through a supply flow control element and an exhaust flow control element, respectively. A tracking one of the two control elements has its flow controlled in response both to the measured pressure in the space and to an indication of flow through the other, driving flow control element. The flow control elements are adapted to provide a designed, at least nominal effective leakage for the space with changes in the pressure differential between the space and at least one of the gas supply and gas exhaust. For preferred embodiments, the effective leakage is achieved by either mechanically or electronically modifying the flow/pressure characteristic of at least one of the valves to have a designed, at least nominal change in flow for changes in pressure across the element.

Abstract: A damper control apparatus for a fume hood which has a moveable sash, and wherein the damper control apparatus includes an axle assembly borne by the fume hood, a cable assembly borne by the sash and disposed in force transmitting relation relative to the axle assembly, and a damper borne by the fume hood and disposed in force receiving relation relative to the axle assembly and moveable along a path of travel into assorted operational positions which correlate with the position of the sash thereby regulating the amount of air withdrawn from the fume hood.

Abstract: Apparatus for use in determining the position of an object such as a sash door of a laboratory fume hood which has an elongated base member for attachment to the fume hood adjacent the sash doors. It includes an electrical switching means having an elongated electrical resistance means that provides a signal indicative of the position of a sash door, and an actuator means associated with each sash door adapted to move when the sash door is moved. The actuator means includes an actuator assembly positioned to operate the switching means at a switch location that varies as the sash door is moved. The actuator means includes a linkage means that permits accurate operation even though there is undesirable movement of the door relative to the base member.

Abstract: In the air flow control system of a laboratory building module, pressurization of corridors and other residual areas can be maintained neutral in relation to the outdoors by balancing the entire intake or supply flow rate and the entire exhaust rate. The laboratory rooms have various forms of fume hoods whose face velocities at their sash openings is regulated variously, either in response to sash position transducers or in response to face velocity sensors. Fume hoods having two sashes provide two sash-position transducers whose composite output represents the sash opening. A fume hood that relies on sensing of face velocity for correlating its exhaust flow rate with its sash opening utilizes the composite output of multiple face velocity sensors. Exhaust flow rates of fume hoods are regulated so as to increase more rapidly for greater sash openings than for smaller sash openings.

Abstract: A method and apparatus for controlling a fluid flow valve with a linear control loop such that the error signal utilized to actuate a variable rate controller for moving a valve control element or for controlling another valve control parameter is the same for a given control parameter change regardless of the current control parameter value or the current or desired fluid flow through the valve. A non-delayed indication of current fluid flow is also generated.

Abstract: This invention relates to a fume hood controlling method and apparatus which reduces the amount of replacement air required to operate a fume hood by permitting the fume hood to operate at a relatively low face velocity in the absence of a containment affecting condition, but which is capable of detecting the occurrence of a containment affecting condition, such as the presence or movement of a user within a selected area of the face of the fume hood, and of increasing face velocity to a selected level in response to such detection. When the detected condition no longer exists, the control automatically returns the fume hood to the lower face velocity, preferably with a time delay. Maximum replacement air volume and minimum replacement air volume may also be controlled in response to such detection.

Abstract: A fume hood controller utilizing feed forward and closed loop control to maintain a constant average face velocity of air entering the fume hood. A sash position sensor provides the controller with a signal indicative of the area of the fume hood opening. An air flow sensor provides the controller with a signal indicative of flow rate. Fast response to a change in sash position is provided by feed forward control which adjusts an air valve or fan to provide a constant face velocity. After initial adjustment by the feed forward control, closed loop control is operable to fine tune the air valve or fan to provide highly accurate control of face velocity. Emergency control is also provided to drive the air flow to a maximum rate when an emergency exhaust button located on the fume hood is pressed.

Abstract: In the air flow control system of a laboratory building module, pressurization of corridors and other residual areas can be maintained neutral in relation to the outdoors by balancing the entire intake or supply flow rate and the entire exhaust rate. The laboratory rooms have various forms of fume hoods whose face velocities at their sash openings is regulated variously, either in response to sash position transducers or in response to face velocity sensors. Fume hoods having two sashes provide two sash-position transducers whose composite output represents the sash opening. A fume hood that relies on sensing of face velocity for correlating its exhaust flow rate with its sash opening utilizes the composite output of multiple face velocity sensors. Exhaust flow rates of fume hoods are regulated so as to increase more rapidly for greater sash openings than for smaller sash openings.

Abstract: Methods and apparatus for controlling the flow of fluid around an object which include means to periodically vary or fluctuate the direction, speed or magnitude of the fluid flow. The fluid flow is particularly controlled to control eddy formation. The fluid is preferably a gas or vapor.

Abstract: An apparatus for sensing the extent to which the sash or sashes covering the access opening of a fume hood are open. The apparatus includes a source of electromagnetic energy at a selected AC frequency below 10.sup.6 MHz, with a preferred frequency range being from 10 KHz to 100 KHz. The source preferably includes a wire coil connected to an oscillator of the selected frequency with the detector for the AC signal also preferably including a wire coil. Suitable elements are also provided for controlling the amount of electromagnetic energy from the source wire coil which reaches the detector wire coil as a function of sash opening.

Abstract: A system whereby the pressure of a room containing one or more fume hoods, such as a laboratory, is to maintained at a predetermined level relative to the pressure of a reference space in the building, which may be the pressure in an adjacent corridor or an adjacent room or the like. The system involves a room controller which is part of the heating, ventilating and air conditioning apparatus of the building. The room controller is of the type which can receive electrical signals from each fume hood controller, which signals are proportional to the volume of air that is being exhausted through each fume hood. The volume indicating signals communicated from each of the fume hood controllers to the room controller enable the system to modulate the volume of air that is being supplied to the room and thereby maintain the differential pressure at the desired level with relatively quick response times.

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.