The Gavita – FB1 Fan Controller Module allows you to balance power to the intake and extraction fans. Extra filters and ducting influence the airflow and may lead to overpressure in the grow room. With the AC fan or EC fan balancer, you can control the inlet or extraction fans to achieve a balance between these 2 airflows. To maintain optimum pressure in the grow room, you must balance both the extraction and intake fans. Offset the intake fan by up to 70% to balance flow of air in your grow room.