What boundary methane concentration distinguishes ERZ1 from ERZ0?

• A. 0.5%
• B. 2%
• C. 0%
• D. 5%

Answer: (B)

In mine gas management, the atmosphere is split into zones based on how much methane is in the air. ERZ0 is the normal working environment with methane kept below the regulatory limit, while ERZ1 is a gas-containing area where methane has reached the level that requires additional safety measures and monitoring. The boundary between these two zones is that regulatory threshold for methane concentration. Crossing it means you must apply enhanced controls—continuous gas monitoring, stricter control of ignition sources, expanded ventilation considerations, and updated emergency planning. The other figures don’t represent that dividing line: one option would still be considered ERZ0 if methane is below the threshold, another would indicate no gas hazard, and the remaining relates to a higher explosion-risk level than the ERZ0/ERZ1 boundary.