If the general body methane concentration around a longwall shearer reaches 1%, what must happen?

• A. The detector must automatically activate a visible alarm to warn the operator.
• B. The machine must immediately shut down and ventilate automatically.
• C. Only the control room is notified; no local alarm is triggered.
• D. No action is required until 2% is reached.

Answer: (A)

The essential idea is that gas monitoring uses threshold-driven alerts to prompt quick local action. When methane in the general body air around the longwall shearer reaches about 1%, the system must automatically trigger a visible alarm at the operator’s location. This immediate local warning gives you the chance to respond early—increase ventilation, inspect for gas sources, and adjust operations before concentrations rise further. At this level, automatic shutdown would be unnecessarily abrupt and could disrupt operations without improving safety as effectively as an early alert. Merely notifying the control room wouldn’t provide immediate eyes-on awareness where the operator is, and waiting until a higher concentration (like 2%) would reduce the safety margin and risk reaching a more dangerous level.