If the detector protecting an auxiliary fan fails, what action is required to keep the fan running, and in which situation does this not apply?

• A. Continuously monitor the general body at the fan with a portable methane detector and disconnect the power if it exceeds 1.25%; this does not apply in a drift or shaft driven from the surface in material other than coal.
• B. The fan must be automatically shut down with no manual intervention.
• C. No action is required and the fan can continue regardless of detector status.
• D. Switch to an alternative ventilation path until detector is repaired.

Answer: (B)

The main idea is that protective detectors for an auxiliary fan act as an interlock to keep ventilation safe. If that detector fails, you cannot rely on the fan continuing to run without monitoring for gas or other hazards. The safety requirement is to automatically shut the fan down with no manual intervention, so the system stops and hazards aren’t missed while the detector is out of service. This automatic shutdown prevents unmonitored airflow from dispersing methane or other gases.

There is an exception: this automatic shutdown requirement does not apply in a drift or shaft driven from the surface when it is in material other than coal. In that particular setup, the normal interlock rule isn’t mandatory, reflecting the different conditions and controls in that configuration.