Where must methane detectors be located in the Longwall return?

• A. In the goaf
• B. In the longwall return airway within 150 m outbye of the corner of the tailgate block side rib line and the longwall coal face
• C. In the return airway of a vent split
• D. In the longwall return airway within 150 m outbye of the corner of the tailgate block side rib line and the longwall coal face

Answer: (D)

Detectors are placed in the longwall return airway to sample air that has already passed the face and goaf, giving early warning of methane before it reaches the main exhaust. Positioning them within 150 m outbye of the corner where the tailgate block side rib line meets the longwall coal face ensures the detector sits in the part of the return that collects gas coming from the face and goaf and moving toward the surface, so responses (like increasing ventilation or halting operations) can be promptly triggered. If detectors were placed in the goaf or in a vent split, they wouldn’t reliably reflect the methane levels in the return path or could miss gas that is migrating toward the main return. So the required location is in the longwall return airway within 150 m outbye of that corner and the longwall face.