Abstract: A generally closed lab hood having an opening closable by a movable door and connected to a variable-throughput suction source has a vent-control system having a sensor for detecting a velocity of flow of air into the hood and for generating an output corresponding to the detected velocity. A controller connected to the sensor and to the variable-throughput suction source receives the output and operates the suction source to set throughput of the source at a level corresponding to the output so that as the detected velocity increases the throughput of the suction source is increased and vice versa. The controller includes a sensor tube having an inner end opening into the hood and an outer end opening outside the hood and a sensor in the tube for detecting the velocity of air-flow therethrough. This tube is offset from the opening. The controller operates proportionally to set the throughput of the suction source relative to the air-flow velocity.

Abstract: An air diffuser assembly for use in combination with an underfloor air distribution system, where the system includes in part a cavity under a floor, having an upper surface, transmitting air under pressure to selected locations above the floor. The air diffuser assembly comprises first and second annular rings threadably engaging one another and secured respectively to above and below the floor, where the first annular ring includes an annular shoulder for receiving a grill assembly. The grill assembly is seated on the shoulder and is in communication with the space above the upper surface. The grill assembly further includes a centrally disposed, downwardly extending, vertically adjustable rod mounting a circular basket at its free end. The basket includes an array of through holes for delivering pressurized air from the underfloor cavity to the diffuser assembly, and means, such as a rod, connecting the basket to the grill assembly to prevent rotation of the basket.