Abstract: A centrifugal fan having a damper control system located away from the air flow path is disclosed. The control system includes a rotatable shaft located outside of a fan housing wherein rotation of the control shaft actuates a plurality of shafts and rods to move an annular damper located within the housing into an open position away from the centrifugal fan blades and to a closed position coaxially over the fan blades thus substantially restricting the flow of air through the centrifugal fan. The dampers are mounted for translation on two support rods located on opposite sides of the centrifugal fan. The dampers ride on a support system including a plurality of ball bearings that are in tangential contact with the support rods thus providing high-pressure contact surfaces between the bearings and the support shafts which act to keep the path of travel of the bearings on the rods free of debris so that the dampers have unobstructed motion between the open and closed positions.

Abstract: A ceiling structure for retaining air filter panels having a grid of interconnected rails. Each rail has a recessed channel for containing a light fixture so that the light fixture does not hang below the ceiling surface. The structure may also include hanger hooks attachable to the rails for suspending fixtures, wall panels, and pivoting wall headers to permit angled arrangements of wall panels. The light fixture attached within the channel is an extruded panel that snaps into the channel and which includes standard light tube connectors.

Abstract: A clean room diffuser panel for positioning below a ceiling grid mounted filter element. The diffuser panel is perforated throughout its area with increased size and density of perforations in a peripheral region to provide increased airflow beneath the ceiling grid. The peripheral regions are further angled or provided with directional vanes to create a lateral airflow beneath the ceiling grid.

Abstract: A clean room is supplied with air at a controllable velocity from a blower with a variable damper mechanism. The ceiling of the clean room is comprised of a plurality of panels of particulate filter material. Associated with at least some of said panels are air dampers comprised of first and second adjacent perforated plates. The first plate is fixed and the second plate is mounted for translational movement relative to the first. By moving the second plate relative to the first, the perforations therein are selectably opened or occluded, permitting the air passing through each panel to be regulated. Air flow through the room as a whole is controlled by the variable air flow feature of the blower.

Abstract: A centrifugal fan in which the cone and wheel have a telescoping relationship to vary the rated capacity of the fan. The mechanism effects the relative movement manually, or by a servo arrangement responsive to system pressure. The telescoping relationship includes an anti-recirculation sleeve on the cone. The wheel and cone can be moved to effect engagement of the cone and the wheel back plate to cut off the fan, when in a parallel arrangement, and to arrest wheel movement, after the drive to the wheel has been stopped. In another aspect, the cone and wheel are bodily stationary and a separate movable flow control sleeve is positioned to control flow.