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. As a result, it improves the working environment, protects workers' health and enhances the working efficiency. All the ventilators adopt American UBC bearings, free lubrication. Supporting brackets are all made of stainless steel, which has very good corrosion-resistant ability. Its significant characteristics: no energy cost, free maintenance, strong ventilation, high sensitivity, no noise, stable and durable,dehumidification, anti-sweat and rain-proof. Model No.:400 Material: stainless steel Amount of Blades:25pcs Total Height:580/430mm Turbine Diameter:630mm Ventilation Diameter:530mm