Improved apparatus for collecting particles from air comprises a cyclone (13) having air inlet (14) and outlet (15) means, means maintaining an airflow there through and means (28) delivering a collecting fluid from a reservoir (26) to particles separated from the air flow in the cyclone (13), in which the air inlet means (14) is associated with means for heating (30) the incoming air. The apparatus, which is optionally provided with enclosure means for trapping heat, prevents freezing of the collecting fluid at temperatures near to and even below 0 grade C.