Where must the visual alarm be visible when the automatic methane detector located in the intake airway at the interface between a NERZ and ERZ1 detects the prescribed concentration of methane in the general body?

• A. On the machine
• B. In the control room
• C. At the interface
• D. In the mine office

Answer: (C)

The key idea is that a visual alarm for a methane detector should warn people where they move between zones and could be exposed to the hazard. When the detector sits in the intake airway right at the boundary between zones, placing the visual alarm at that same boundary guarantees visibility to workers in the general body on either side. If the alarm were only on the machine, in the control room, or in the mine office, workers passing through the interface or working in the intake area might not see it in time, which undermines rapid protective actions. By locating the alarm at the interface, anyone entering or working in the general body near the boundary will notice it promptly and can take appropriate steps, such as increasing ventilation or evacuating if needed.