RAF series fan is a new type of roof fan developed by European and American advanced technology. It has a smooth shape design, a fine proportion and fine workmanship. It meets the requirements of high quality building for exposed equipment. The specific advantages of large capacity, high pressure, low power consumption, light weight, compact structure, widely used in roof ventilation and senior civil construction machinery, chemical, rubber, pharmaceutical, textile and other industries workshop. It is made of two kinds of structure: RAF model adopts conical hub and twisted wing blade, which is suitable for ventilation in middle and low pressure and large flow occasions. The RTCX-II type adopts the optimized centrifugal impeller, which is suitable for the air exhaust ventilation with higher pressure requirements. The utility model can be made into anticorrosive explosion-proof type according to the different conveying medium. According to the user's needs can be equipped with gravity check air return valve, maintenance switch, centralized control box and other accessories to buy.