Each dryer can be operated in either passive (natural convec- tion) or active mode (forced convection). The passive mode of greenhouse dryer works on the principle of thermosyphic effect. The humid air gets ventilated through the ventilator provided at the roof or through the chimney of the dryer. Humid air is venti- lated by the help of an exhaust fan provided at the ventilator. It is generally provided in the upper portion of the west wall