Abstract: The invention relates to an air cleaner in the form of a cyclone separator comprising a cyclone chamber (2), a gas-feeding nozzle (11) which is directed tangentially to the wall (12) of the cyclone chamber, and a gas outlet (7). The invention is characterized in that the cyclone separator comprises a liquid trap (9, 13) arranged in the wall (12) of the cyclone chamber. Further the nozzle and the liquid trap extend along substantially the entire height of the cyclone chamber. The liquid trap comprises axial grooves (13) and a chamber (9) having an inlet gap (15) which connects the chamber (9) with the cyclone chamber (2) for diverting liquid droplets.