The headline above is a reminder that a fan and a damper, when assembled, become a fan + damper system, which is more than a simple sum of the two individual items of equipment.
They may be operated independently of each other, but their functions become interdependent. Because of this interdependent relationship, some close attention has to be given to the proper selection and matching of fan and damper. A fan inlet may be connected to other ductwork, either directly or via an inlet box, or the inlet may be unducted. This article considers only fans that have unducted inlets.