Bypass Variable Air Volume units are designed to maintain optimum occupant comfort by varying the amount of conditioned air from the air handler by  bypassing the excess air into the ceiling plenum or back to the air handler through return air duct. Single duct pressure independent variable air volume units are designed for lower operating cost by using less fan and refrigeration energy. The primary function of the air terminal unit is to regulate the conditioned airflow into an occupied zone in response to a control signal. Conditioned air volume is precisely regulated according to demand. Units are available with a wide range of control packages to suit any application.