The ideal ventilation system is determined by your budget and your imagination. However, there are two main theories of room design: the open room and the closed or “perfect” room. br br For more information, visit: br An open room is one in which air is constantly being circulated in and out. Airflow in an open room is very important because it is necessary for exhausting the warm O2 rich air and refilling the room with cooler natural air, which has higher levels of CO2. In doing so, you are also helping to maintain a healthy temperature for your plants.