Abstract: The invention relates to an air movement system comprising a centrifugal fan unit, wherein the centrifugal fan unit comprises a centrifugal fan coupled to a drive unit, a control unit operationally coupled to said drive unit, an inlet piece forming a inlet duct to the centrifugal fan, which inlet duct has an end facing the centrifugal fan, and an outlet duct, wherein the inlet piece is provided with a first pressure tap and a second pressure tap, the second pressure tap being positioned at distance from the end of the inlet duct facing the centrifugal fan, and the control unit is configured to measure a pressure difference between the first and second pressure tap and to control the centrifugal fan in dependence of the measured pressure difference, characterized in that the first pressure tap is positioned at the end of the inlet duct facing the fan, and in that said control unit is adapted to maintain a set airflow rate out of said outlet duct based on said measured pressure difference via controlling of the