Abstract: A sheet metal construction system is provided with a support strut having an elongated channel. A piece of sheet metal having an aperture is positioned on the strut with the aperture positioned over a portion of the channel. A rivet is received within the aperture and extends into the channel where it grips the strut. In this way, the aperture in the sheet metal can be positioned anywhere along the length of the channel and there is much greater freedom in the placement of rivets. The strut is also provided with channels for receiving braces and hangers for suspending a finished sheet metal product, such as a plenum for a clean room.

Abstract: A centrifugal fan is provided with an inlet cone that serves to measure air flow through the fan. The inlet cone has a flared inlet for receiving air, a narrow throat, and a flared outlet for expelling air into the center of a rotating fan wheel. Pressure taps are provided to measure the static pressure at the inlet and the throat. The difference between these pressures, adjusted for the empirically determined characteristics of the inlet cone, can be used as an indication of air flow. In one aspect of the invention, a controller monitors the pressure differential, calculates a flow rate based on the characteristics of the cone, and adjusts the fan speed to maintain a desired air flow.

Abstract: A clean room ventilation system having a diffuser panel attached to a ceiling grid, with a filter element positioned well above the panel. The diffuser panel is perforated throughout its area with increased size and/or density of perforations in a peripheral region to provide increased airflow beneath the ceiling grid. The peripheral regions may further be angled to create a lateral airflow beneath the ceiling grid.