A track-based mobile system for use with processes generating air-borne pollutants, for preventing contamination of the atmosphere. An enclosure for containing air-borne pollutants and a filtering system for removing the pollutants from the air are movable as a unit along a track for use at a plurality of worksites. The unit is openable at opposing portions facing the track so as to be able to pass over workpieces at the plurality of work sites. The filtering system includes intake tubes, and dampers to enable the selection of air-flow patterns within the enclosure.