The air polluted by oil mist or coolant is channelled inside the centrifugal filter crossing the inlet providing a grid so as to prevent the suction of solid material. A conic diffuser guarantees the uniform distribution inside the drum of the mist and vapour that are centrifuged at high speed and then pushed towards the filtering panels. While crossing the panels, the particles undergo a coalescence effect turning into droplets and then discharged through a drainpipe. Cleaned air is thus ducted towards the upper part of the filter to be possibly treated with a final cartridge or an electrostatic filter FEF.