GDF series circular duct fan is a new type fan designed based on advance technolody.It adopts low noise external rotor combined with centrifugal impeller by direct driving.The circular inlet and outlet use the same dimensions connected directly with the coaxial pipelines and with-out machine room.so as to save cost of pipeline design and installation It has features of high flow rate as pipeline fan,low noise and vibration as multi-vane fan.It has fretures as low noise,energy saving,compact size,convenint to install,reliable operation,etc.And it's widely used for hotel,restaurant,high grade meeting room,supermarket,high level villa,hospital and civil building,etc.Which required air delivery and exhausting with low noise.