At what percentage of methane gas is equipment prohibited to operate in?

• A. 0.5% or above
• B. 1.0% or above
• C. 2.0% or above
• D. 0.1% or above

Answer: (B)

Understanding safe methane limits is crucial because methane can ignite if an ignition source is present in an air–gas mix. The rule is that equipment must not be operated when methane reaches one percent or more. This action level provides a safety margin to reduce gas concentration through ventilation before ignition risk increases. While methane becomes explosive in air roughly between five and fifteen percent, the one-percent threshold is a protective precaution to keep operations within a safer range and allow time to address ventilation. Lowering to half a percent or a tenth of a percent is more conservative than needed for ignition risk, and waiting until two percent would leave less margin for safe operation. Therefore, one percent or above is the point at which operation is prohibited.