What is the CH4 limit for engine or machine power?

• A. Power 1.0%
• B. Power 1.25%
• C. Power 1.5%
• D. Power 2.0%

Answer: (B)

This item is about the safety limit for methane (CH4) concentration around power equipment in coal mining. The standard sets 1.25% by volume as the maximum CH4 level for engine or machine power. This limit provides a practical safety margin: if methane in the vicinity of the engine stays at or below this level, the risk of ignition from ignition sources on or near the equipment is kept lower, allowing normal machinery operation under the mine’s gas management rules. If methane around the equipment were higher, more protective measures or explosion-protected equipment would be required. The other options are not the regulatory limit used for engine or machine power in this context.