The roof ventilation fan applies the theory of convection between natural wind and air to accelerate and transform any parallel airflow into vertical so as to improve the indoor ventilation. The hot air rises and cold air falls, which makes the fan rotate. So the indoor heat, stink and dust are exhausted effectively. It also can effectively remove indoor soot, smoke, odor, moisture, heat, decorative harmful gas, dust, human metabolism and other dirty volatile mixed-doped odor as well as viruses and bacteria invasion. As a result, it improves the working environment, protects workers' health and enhances the working efficiency. It is widely used in warehouse, toilet, factory, workshop, stadium, tennis hall, assembly hall, garage, paper mill, galvanization factory and coating factory. Advantages: 1)High-efficiency ventilation. 2)High-quality stainless steel body. 3)Easy and fast installation. 4)Environmental protection, energy saving and no electricity cost. 5)Stable and durable, dehumidifier, anti-sweat and rain-proof. 6)High sensitivity and no noise. 7)All the ventilators adopt American UBC bearings, free lubrication. Supporting brackets are all made of stainless steel, which has very good corrosion-resistant ability. Specification: Model No.: AP200 Material: Stainless steel Amount of Blade: 20PCS Total Height: 350mm Turbine Diameter: 330mm Ventilation Diameter: 200mm Base plate Dimension: 330mm*330mm