The present concepts maintain forward flow and prevent reverse flow of heat-transferring media. A first zone and a second zone are proximate to each other. A first fan moves air through the first zone in a forward direction. A second fan moves air through the second zone in a forward direction. The speed of the first fan is compared with the speed of the second fan. If the first fan speed is slower than the second fan speed, then the first fan speed is adjusted to match the second fan speed. Therefore, reverse airflow in the first zone is prevented.