The 4-68 series fan belongs to centrifugal ventilation fans, which are used for indoor ventilation and air exchange in general factories and large buildings, as well as for boiler ventilation and induced draft in thermal power plants. The impeller has been balanced and calibrated, running smoothly. The casing is snail shaped, and the air inlet is streamlined. There are two types: right-handed and left-handed, with various outlet positions and transmission modes. It has the characteristics of high efficiency and flat pressure curve, and can provide stable gas pressure for ventilation systems.