Patent ID: 8720532

Claim:
An airflow control apparatus comprising: a controllable airflow resistance aligned with an airflow path of a plurality of airflow paths; a sensor that detects an airflow condition in at least one of the plurality of airflow paths; a controllable-speed fan coupled into an airflow path of the plurality of airflow paths; a controller coupled to the controllable airflow resistance and the sensor, the controller comprising a logic that controls the controllable airflow resistance in combination with the controllable-speed fan to manage airflow recirculation based on the airflow condition detected by the sensor; a plurality of controllable airflow resistances; and a plurality of fans coupled into multiple airflow pathways, the controller controllably coupled to the plurality of controllable airflow resistances and to the plurality of fans, and comprising a logic that determines an airflow recirculation condition based on the airflow condition and adjusts the controllable airflow resistances and the controlled-speed fans in combination, wherein the logic detects a recirculation condition and responds to the detected recirculation by reducing fan speed in at least one selected fan and increasing a selected airflow resistance.