Check the power connection.
Check possible phase loss.
Check that the electric wiring of the fan is correct.
Adjust the damper in the hood.
Check that the fan impeller rotation in the right
direction. Compare with the arrow on the label. If
the impeller rotates in the wrong direction, the fan
only gives 40% of its possible air volume. Contact a
qualified electrician if the impeller rotation must be
reversed.
Replace the filter cartridge.
Check the hose of the extraction arm for holes.
Check the fan for a blocked outlet/inlet or other
damages.