In most HVAC systems, the final energy transport medium is moist
air—a mixture of dry air and water vapor. This is conveyed through
filters, heat exchange equipment, ducts, and various terminal devices
to the space to be air-conditioned. The power to move the air is supplied
by fans. This chapter discusses fans and duct systems, together
with related subjects such as grilles, registers, diffusers, dampers, filters,
and noise control.