* model 4-2x79e and model 4-79a centrifugal fan convey air and other non-hypergolic gas which are not harmful to the human body and will not cor-rode steelmaterials. the adhesive materials are not allowed in the gas. its containing cust and hard particles should not exceed 150mg/m³，gas temperature not exceed 80t. it has sound pnoumatic, performance. the paddle wheel, pulley have been implemented with static, dynamic balancing correction. therefore it has features such as balanced running little vibration, high efficiency, long life etc. it is widely applicable for the indoor ventilation, air-exchange, exhaust in the mining and industrial enterprises, large-size architectures, guesthouses, restaurants etc.