In most labs, there are typically only a few active fume hoods in the system emitting limited levels of contaminants. These contaminants are significantly diluted by the relatively clean air that is manifolded from other locations. Although, the laboratories operate in these relatively clean states for extended periods of time, the exhaust fan systems run at high exit velocities (e.g., 3,000 ft/min or higher). As a result, these systems frequently operate at much higher total flow rates than required using significantly more energy than necessary. Many assume that exhaust fans are required to operate at 3,000 ft/min (minimum).
Read why this is a common industry misconception.
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