Abstract: A fan unit for a building's air handling system comprising a support structure including a front wall with an air inlet opening formed therein and a bladed fan wheel rotatably mounted on the support structure about its central axis and having an axial air intake on a front side thereof confronting the inlet opening. The fan wheel has an annular air outlet extending about its circumference. A fixed centerbody directs air flow into and within the fan wheel and extends along the central axis from a relatively narrow front end located in the air inlet opening to a wider rear end located within the fan wheel. This centerbody has an annular exterior surface which curves outwardly in a section thereof adjacent the wider rear end. The centerbody extends through the axial air intake of the fan wheel. Support struts rigidly support the centerbody in a fixed position. Preferably the centerbody is filled with sound attenuating material.