Ventilation is extremely important for the growing crop of marijuana; this is because the plants emit waste through the stomata on their leaves. The indoor grower is faced with simulating the outdoor environment, this means also creating the elements of wind, rain and sunlight. Ventilation is a part of this and without proper ventilation the toxins that are emitted through the leaves will not be able to evaporate and can cause the leaves to become clogged. This can result in disease in the marijuana plants. In a large grow room, the use of a fan with a thermostat will work well and for the closet grower, opening and closing the door will provide the needed ventilation.  The large indoor crop might need the use of a dehumidifier to not only keep the room at the correct humidity level, but also to help with the proper amount of ventilation for the pot plants.