Sketch Map of Engine
Vertical Airflow
The clean air flows up and out from the bottom, and then returns back for recycle usage through the bottom hollow floor.
Random Airflow
The clean air flows down from and up ceiling, and then returns back for recycle usage from down-side.
Level Airflow
The clean air flows out from one of the side, and then returns back for recycle usage from the other down-side.
