Circular duct fans series are combined with domestic and foreign advanced technology on design. The sizes of inlet duct and outlet duct are the same. Connected the fan and piping directly could save design and install cost on the piping. Special housing could reduce noise and vibration, best design on the impeller base on aerodynamic. Design for blow, exhaust, circle, renew and filtration could be used in hotel, marketplace, gymnasium, supermarket, store room and most of public place.