If methane reaches nine percent, the greatest danger is:

• A. Explosion
• B. Fire
• C. Toxic poisoning
• D. Asphyxiation

Answer: (A)

The main idea is the flammability range of methane in air. Methane forms an explosive mixture with air from about 5% up to around 15% methane by volume. At nine percent, the mixture sits squarely inside that range, so a spark, flame, or hot surface can ignite it and cause a violent explosion. This risk is more dangerous in a mine than a simple fire or gradual oxygen depletion, because the explosion can propagate rapidly and release a lot of energy in a confined space. Methane itself isn’t toxic, so poisoning isn’t the primary concern at this concentration; while gas can displace some air, the immediate, most dangerous outcome when the gas is within the flammable range is an explosion.