Abstract: A method and apparatus for controlling a fume hood. A containment condition, i.e., a condition that may affect containment of potentially harmful substances in the hood, may be detected, and information regarding the detected condition sent by wireless signal. A fume hood controller may control at least airflow in the hood based on the information contained in the wireless signal.

Abstract: Methods and apparatus for recirculating air in a controlled ventilated environment. In one example, recirculation of air from one or more rooms in a multiple room ventilated environment having a common source of supply air is controlled such that minimum ventilation and thermal load requirements for each room are satisfied independently, so as to facilitate a reduction in the amount of fresh outside air required for the environment. In another example, the controlled airflows in each room may be based additionally on respective air quality levels of the air drawn from each room. In one aspect, if contaminants are detected in one or more rooms of the ventilated environment, the amount of air recirculated from a contaminated room back to the environment may be controlled based on a detected level of the contaminant and a dilution ratio of any returned contaminated air to the total uncontaminated air supplied to the environment.

Abstract: Methods and apparatus for recirculating air in a controlled ventilated environment. In one example, recirculation of air from one or more rooms in a multiple room ventilated environment having a common source of supply air is controlled such that minimum ventilation and thermal load requirements for each room are satisfied independently, so as to facilitate a reduction in the amount of fresh outside air required for the environment. In another example, the controlled airflows in each room may be based additionally on respective air quality levels of the air drawn from each room. In one aspect, if contaminants are detected in one or more rooms of the ventilated environment, the amount of air recirculated from a contaminated room back to the environment may be controlled based on a detected level of the contaminant and a dilution ratio of any returned contaminated air to the total uncontaminated air supplied to the environment.

Abstract: A fume hood sash sensor uses multiplexed sensors to measure sash position. The sensor transmitter or receiver elements may be multiplexed. Furthermore, the sensor may employ passive, passive remote powered transponder, or powered transponder elements on the sashes to measure sash position.

Abstract: A networked air measurement system includes a sensor capable to measuring a characteristic of an air sample, the sensor having an air inlet port; a backbone tube in communication with the air inlet port of the sensor; a plurality of air intake valves in communication with the backbone tube, air admitted through one of the plurality of air intake valves communicated into the backbone tube; an air flow induction device in communication with air in the system, air moved by the air flow induction device from the plurality of air intake valves through the backbone tube, to the sensor; and a controller connected to the sensor and to each air intake valve, the controller executing a control sequence which opens and closes air intake valves to admit air and form air samples communicated to the sensor. The system controller may use time intervals or measurements of air samples to determine proper times at which to open individual ones of the air intake valves.

Abstract: A process control system includes a high speed serial backbone communications network, interconnecting a plurality of microprocessor based nodes that each act as the master to a high speed serial branch network comprising device controllers, such as air flow valve controllers and transducers. The primary network may operate in a time division multiplex mode whereby a node acting as a synchronizing station periodically issues a synchronizing signal that commands each node to execute a branch network control sequence, during which each node gathers and operates upon data it collects from the device controllers within its branch network, and issues commands based thereon to the branch network. An ensuing communications sequence also triggered by the synchronizing signal enables each node on the primary network to transmit a command or a response to any other node and, through such other node, to any device controller in any branch network of the system.

Abstract: A control is provided for a facility which has at least one pressurized room which control facilitates the making of selected changes in offset between the room and a space external thereto while maintaining a desired air flow balance. This is accomplished at least in part by making changes in the air flow for the external space in connection with such offset changes.

Abstract: Precision gas flow control is provided utilizing a first coarse gas flow control element and a second fine gas flow control element. The second element is selected and operated to pass only a fraction of the flow passed by the first element. The elements may be connected either in series or in parallel so that at least a portion of the gas flow passes through each flow control element. Control circuitry is also provided which may be responsive at least in part to an indication of desired gas flow through the device for controlling the first element to provide a coarse gas flow adjustment and for controlling the second element to provide a fine gas flow adjustment. In some applications, only fine flow adjustment may be provided. Where the elements are being utilized for example as the tracking flow control elements for a sealed enclosure, either the fine flow control element or both elements may also be made responsive to pressure errors in the enclosure.

Abstract: A system is provided for detecting presence and/or motion of a person or other movable entity within a selected space. Detection is accomplished by detecting reflected light or other radiation from the space, presence being signified when detected radiation differs from an established background, either up or down, by an amount exceeding a predetermined threshold. Blending of the entity with the background is avoided by viewing the entity at at least two different angles with different background, for example by use of two spaced detectors, and variations in background are automatically compensated for when a presence indication persists for a selected period of time after the last motion indication is received. The background is updated to the current level when this occurs.

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 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: A mechanism is provided for operating multiple air flow control valves from a single actuator. The mechanism includes a yoke mounted to move with the drive shaft of the actuator and having a leg facing in the direction of each valve. The leg is resolvably connected, preferably by a link pivotably connected at each end, to a lever connected at its other end to a control shaft for the valve.

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: An apparatus for sensing the extent to which the opening of a fume hood is uncovered by the hood sashes, and is particularly adapted for use with hoods having sashes which are moved horizontally. Radiation from a radiation emitter, such as an optical or a magnetic emitter, are sensed by corresponding detectors. For some embodiments of the invention, there is relative movement between the emitters and detectors as the sashes are moved to cover or uncover the opening, the movement between the emitter and the detector being such that the amount of radiation detected by the detectors is proportional to the uncovered portion of the opening. The relative movement may be accomplished by, for example, having the detectors fixed and having the emitters mounted to the sashes or by having the detectors mounted to some sashes and the emitters mounted to other sashes. A unique magnetic emitter is also provided with enhanced flux throw.

Abstract: Method and apparatus for varying the make-up air volume of an HVAC system used in conjunction with a laboratory fume hood. The invention maintains a constant difference in air volume between the total air volume exhausted from the laboratory, including the variable fume hood exhaust volume and the make-up and supply air provided by the HVAC system. The invention provides a continuous modulation of the make-up air volume which tracks the exhaust volume to maintain a constant preset differential between the makeup and exhaust volumes. The invention includes a preferred embodiment in which a signal from a sash height transducer is used to control the volume of make-up air.