In the event of a detector failing in service, where should a PGD be used?

• A. At the location of the failed detector to continuously monitor CH4
• B. At the mine air intake alone
• C. At the surface only
• D. In the control room only

Answer: (A)

When a fixed CH4 detector fails, the priority is to keep monitoring where the risk is greatest. Use a portable gas detector at the location of the failed detector to continue monitoring methane in that area. This keeps detection tied to the actual environment and potential gas pockets near the working face or detector point, allowing immediate response if gas levels rise.

Monitoring at the mine air intake would not reflect conditions in the area where gas could accumulate, and surface or control room placements won’t provide real-time, location-specific data underground. A portable detector at the failed site ensures timely warnings and appropriate action until the detector is repaired or replaced.