A ventilation system for treatment of agriculture and garden products inside a closed storage premises (7) having a floor (3), walls (4) and a ceiling (5), which ventilation system comprises an air mixing unit (7) equipped with a fresh air intake (8) and an air circulation intake (9) and a mixture lid (21), which in dependence of its extent of opening mixes fresh air with circulation air inside the mixing unit (7), whereby a fan (11), the low side of which is connected to the air mixing unit (7) and the pressure side of which is connected to a distribution channel (43), is arranged to distribute air from the air mixing unit (7) to the storage premises (1), whereby the air mixing unit (7) is arranged at or close to the floor level close to an external wall (4) and an exhaust air outlet (10) for the circulation air is arranged in the said external wall (4) at a maximum distance from the air mixing unit (7), which distance corresponds to the largest width or height of the air mixing unit (7).
