System for controlling laboratories with fume hoods

A method for controlling laboratories having fume hoods comprising the steps of:

• sensing a state of each laboratory having a fume hood;
• providing information corresponding to the state of each laboratory with a fume hood to a perspective microprocessor associated with each laboratory;
• providing information to a respective microprocessor from a controller at a remote location;
• and
• maintaining a respective laboratory in a predetermined state with the microprocessor based on the information received from the controller and the information corresponding to the state of each laboratory.

Apparatus for monitoring and controlling a fume hood of the type which has an opening and at least one moveable sash door adapted to at least partially cover the opening as the fume hood sash door is moved, the fume hood having an exhaust duct for expelling air and fumes therefrom, said fume hood being of the type which has a filter housing and filter means for entrapping fumes and effluents, said apparatus comprising:

• means for determining the size of the uncovered portion of the opening and for generating a position signal indicative of the determined size;
• means for measuring the flow of air through the fume hood and generating a flow signal that is indicative of the flow of air therethrough;
• modulating means for varying the flow of air through the fume hood responsive to a control signal being received from a controller means;
• means for measuring the differential pressure across the filter housing and providing an electrical differential pressure signal that is proportional to the measured differential pressure;
• and
• controller means responsive to said position signal and said actual flow signal for controlling the flow modulating means to control the flow of air through the fume hood, said controller means generating a high filter loading signal responsive to said differential pressure signal exceeding a predetermined value.

A system for controlling the differential pressure within a room such as a laboratory or the like of the type which has one or more exit doors which can open either inwardly or outwardly of the room, the room being located in a building having a building heating and air conditioning apparatus, including a central monitoring station, the room having a plurality of fume hoods located within it, the fume hoods being of the type which have at least one moveable sash door adapted to at least partially cover the opening as the fume hood sash door is moved, each of the fume hoods having an exhaust duct that is in communication with an exhaust apparatus for expelling air and fume from the room, said system comprising:

• a fume hood controller means for controlling a flow modulating means associated with each fume hood and its associated exhaust duct to provide the greater of the flow required to maintain a predetermined minimum flow through said exhaust duct or to maintain a desired face velocity through the uncovered portion of the opening;
• said flow modulating means associated with each fume hood and adapted to control the air flow through the fume hood;
• a first emergency switching means located adjacent each fume hood adapted to be activated by a person in the event of a chemical spill or the like, said switching means providing a signal to said fume hood controller means to control the flow modulating means to achieve a predetermined emergency flow rate and providing a signal to the central monitoring station indicating an emergency condition.

A system for controlling the differential pressure within a room such as a laboratory or the like of the type which has one or more exit doors which can open either inwardly or outwardly of the room, the room being located in a building having a building heating and air conditioning apparatus, including a central monitoring station, the room having a plurality of fume hoods located within it, the fume hoods being of the type which have at least one moveable sash door adapted to at least partially cover the opening as the fume hood sash door is moved, each of the fume hoods having an exhaust duct that is in communication with an exhaust apparatus for expelling air and fumes from the room, said comprising:

• a fume hood controller means for controlling a flow modulating means associated with each fume hood and its associated exhaust duct to provide the greater of the flow required to maintain a predetermined minimum flow through said exhaust duct or to maintain a desired face velocity through the uncovered portion of the opening;
• said flow modulating means associated with each fume hood and adapted to control the air flow through the fume hood;
• a first emergency switching means located adjacent each fume hood adapted to be activated by a person in the event of a chemical spill or the like, said switching means providing a signal to said fume hood controller means to control the flow modulating means to achieve a predetermined emergency flow rate;
• a second emergency switching means located outside of the room;
• room controlling means for controlling at least the volume of air that is supplied to the room from the heating and air conditioning apparatus of the building;
• said second emergency switching means providing an emergency signal to said room controlling means and to the fume hood controller means of at least some of the fume hoods in response to a person actuating said second switching means, said fume hood controller means controlling the modulating means to increase the flow rate thereof to a predetermined maximum, said room controlling means controlling the air supply to the room to modulate the flow of air into the room whereby the differential pressure in the room is within the range of about 0.05 and 0.1 inches of water lower than a reference pressure outside of the room, so that any outwardly opening door can be opened by a person inside the room and the differential pressure will not normally force any inwardly opening door open.

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 fume hood being in communication with an exhaust duct for expelling air and fumes from the fume hood, said apparatus comprising:

• means for detecting the position of each moveable sash door and generating a position signal that is indicative of the sash door position;
• means responsive to said position signals for calculating the size of the uncovered portion of the opening;
• means for measuring the actual flow of air through the exhaust duct and generating an actual flow signal that is indicative of the actual flow of air through the exhaust duct;
• modulating means for varying the flow of air through the exhaust duct responsive to a control signal being received from a controller means;
• controller means responsive to said position signals and said actual flow signal for controlling the flow modulating means to generate the greater of a predetermined minimum flow rate signal value or a desired flow rate signal value as a function of the calculated size of the uncovered portion, said desired flow rate signal corresponding to a flow rate that is sufficient to maintain the predetermined average face velocity through the uncovered portion of the opening, said controller means comparing said desired flow rate signal and said actual flow rate signal and generating an error signal indicative of any error that exists by taking a plurality of successive measurement samples of said actual flow rate, determining at least two distinct factors of said error signal from said successive samples and summing the said factors to generate said error signal, said controller means generating and outputting a control signal to said modulating means for selectively reducing said error signal to a predetermined minimum value when said actual flow rate signal exceeds said predetermined minimum flow rate signal value or providing a predetermined minimum flow rate.

Apparatus for controlling the air flow through a plurality of fume hoods to maintain a predetermined average face velocity through an uncovered portion of an opening of each fume hood, each fume hood being of the type which has at least one moveable sash door adapted to selectively cover the opening as the fume hood sash door is moved, each fume hood in communication with an exhaust duct for expelling air and fumes from each fume hood, the exhaust ducts for each fume hood being in communication with an exhaust system, said apparatus comprising:

• means associated with each fume hood for detecting the position of each moveable sash door and generating a position signal that is indicative of the position of such sash door;
• means responsive to said position signals for calculating the size of the uncovered portion of the opening of each fume hood;
• means for measuring the actual flow of air through the exhaust duct in communication with each fume hood and generating an actual flow signal that is indicative of the actual flow of air through the exhaust duct;
• modulating means associated with each fume hood for varying the flow of air through the exhaust duct that is in communication with the respective fume hood responsive to a control signal being received from a controller means;
• controller means responsive to said position signals and said actual flow signal for controlling the flow modulating means associated with each respective fume hood to generate a desired flow rate signal as a function of the calculated size of the uncovered portion, said desired flow rate signal corresponding to a flow rate that is sufficient to maintain the predetermined average face velocity through the uncovered portion of the opening of each fume hood, said controller means comparing said desired flow rate signal and said actual flow rate signal for each fume hood and generating an error signal indicative of any errors that exist by taking a plurality of successive measurement samples of said actual flow rate, determining at least two distinct factors of said error signal from said successive samples and summing the said factors to generate said error signal, said controller means outputting a control signal to said modulating means associated with each fume hood for selectively reducing said error signal to a predetermined minimum value or maintaining a predetermined minimum actual flow.

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 fume hood being in communication with an exhaust duct for expelling air and fumes from the fume hood, said apparatus comprising:

• means for detecting the position of each moveable sash door and successively generating a position signal that is indicative of the position of each sash door;
• means responsive to said position signals for calculating the size of the uncovered portion of the opening;
• means for successively generating an actual flow signal that is indicative of the actual flow of air through the exhaust duct;
• modulating means for varying the flow of air through the exhaust duct responsive to a control signal being received from a controller means;
• controller means responsive to said position signals and said actual flow signal for controlling the flow modulating means, said controller means either generating a control signal value that maintains a predetermined minimum flow rate or generating a desired flow rate signal as a function of the calculated size of the uncovered portion, said desired flow rate signal corresponding to a flow rate that is sufficient to maintain the predetermined average face velocity through the uncovered portion of the opening, said controller means generally continuously comparing said desired flow rate signal with successive instantaneous sample values of said actual flow signal and generating an error signal having a magnitude that is directly proportional to the sum of any calculated integration error, any calculated derivative error and any calculated proportional error, said controller means successively generating and outputting a control signal to said modulating means for reducing said error signal to a predetermined minimum value or maintaining said predetermined minimum actual flow.