If the general body concentration detected at the ERZ/NERZ interface exceeds 0.5%, what must be tripped?

• A. Ventilation fans
• B. Electricity supply to Non intrinsically safe plant in the ERZ1 and NERZ
• C. Emergency stop
• D. Detector reset

Answer: (B)

When there’s a methane-bearing atmosphere, ignition sources become the critical concern. Any electrical equipment that is not intrinsically safe can produce sparks, arcs, or heat capable of igniting gas mixtures. If the general body concentration detected at the ERZ/NERZ boundary rises above a dangerous level, the safest immediate action is to remove such ignition sources by tripping the electricity supply to non intrinsically safe plant in the ERZ1 and NERZ zones. Intrinsically safe equipment is designed to limit energy so it cannot ignite methane, so it can remain energized if it’s certified as IS. While ventilation strategies and detector handling are important for ongoing safety, the mandated step in this high-risk condition is to power down non intrinsically safe equipment to prevent ignition.