In a longwall return airway, detectors must be located in which zones?

• A. In ERZ0 only, regardless of machine movement.
• B. In ERZ1 only, regardless.
• C. In ERZ0 and ERZ1 as applicable when a machine can pass boundaries.
• D. Not required.

Answer: (C)

In a longwall return, gas detection coverage is arranged for boundary zones so that as equipment moves and air flows through different sections, methane and other gases are still detected promptly. Detectors must be located in ERZ0 and ERZ1 as applicable when a machine can pass boundaries. This ensures there are no blind spots where gas could accumulate as the machine crosses from one zone to another, enabling timely alarms and ventilation adjustments. If a machine cannot cross boundaries, the monitoring needs align with the relevant zone, but when crossing is possible, placing detectors in both ERZ0 and ERZ1 prevents undetected gas pockets.