What is the methane explosion range in air?

• A. 0-5%
• B. 5-15%
• C. 15-25%
• D. 25-50%

Answer: (B)

Methane in air is flammable only within a specific concentration window, called its explosive range. For methane, the lower explosive limit is about 5% by volume, and the upper explosive limit is about 15% by volume. Within roughly 5% to 15% methane in air, a flame can ignite and propagate. Below 5% there isn’t enough methane to sustain combustion, and above 15% there isn’t enough oxygen to support burning. So the methane–air explosive range is 5% to 15%.