Backwoods,
My guess is that when the damper is set in the 0 position the remaining path for airflow is not enough for the smoke to backflow. There must be some sort of balance between the open loading door and the intake. Smoke seems to shift flow if the balance of air flow into either opening is not proportional.
My guess is that when the damper is set in the 0 position the remaining path for airflow is not enough for the smoke to backflow. There must be some sort of balance between the open loading door and the intake. Smoke seems to shift flow if the balance of air flow into either opening is not proportional.