For longwall workings, where should the monitoring device be positioned?

• A. At the intersection of the longwall face and the intake airway.
• B. At the mine portal of the intake shaft.
• C. In the control room only.
• D. At the end of the return airway far from the face.

Answer: (A)

Monitoring device placement in longwall ventilation is about ensuring early detection of hazardous conditions at the face. Fresh intake air moves toward the longwall face, where methane, heat, and dust are generated. Positioning the monitor at the intersection of the longwall face and the intake airway places it in the path of this incoming air, providing the quickest and most representative reading of what the face is actually exposed to. This early warning allows timely ventilation adjustments or shutdowns if gas levels rise, protecting workers and equipment. Placing the monitor at the mine portal of the intake shaft or in the control room distances the sensing point from the face and air entering it, making readings less representative and potentially delaying alarms. Putting it at the end of the return airway far from the face monitors exhaust air, not the fresh air supplying the working face, so it fails to detect issues early.