Arched-section tunnels (or headings) in British coal-mines are normally driven by boom-type cutter/loader machines. Ventilation and dust control in the working area are provided by a ducted forcing or exhausting auxiliary ventilation system. Work has been carried out with machine-mounted canopy air curtains and air-curtain tube systems, for the purpose of protecting machine operators from respirable dust when the ventilation system is inadequate for dust control. Canopies provide a zone of cleaned air around the operator's head, while air-curtain tube systems, for use only in exhaust-ventilated headings, confine the dust cloud in front of the operator. Both techniques were found to reduce his dust exposure during cutting operations by between 50 and 70%. The effect on shift-length exposure was naturally somewhat lower. The systems confer considerable benefits in the matter of operator protection, particularly at the return ends of advancing longwall coalfaces. This may not always be seen in statutory respirable dust samples.
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