A longwall at Barnes and Tucker Coal Company's Lancashire No. 20 Mine, near Barnesboro, Pennsylvania, is controlling respirable dust successfully with a bidirectional shearer featuring a small and a large drum and a cutting sequence that keeps face workers in a split of clean air during most of the mining cycle. The longwall unit, which cuts about 800 tons per shift in a 60-in-thick area of the Lower Kittanning seam, has a consistent record of compliance with a 2.0- Mg/m3 federal respirable-dust standard. According to a survey the Mine Safety and Health Administration conducted in 1978, the average face worker's exposure to respirable dust at the mine ranged from 1.1 to 2.0 Mg/m3. In 1981, dust exposure was 0.6 to 1.5 Mg/m3 for designated occupations. Air along the 400- to 500-ft-wide longwall face flows into the tailgate and out through the headgate. A separate split of air from the belt entry returns into the gob entry as well. The longwall panel is supplied with 18,000 ft3/min of air that achieves a face velocity of 200 ft/min.