What is the lower explosive limit of natural gas (methane)?

What is the lower explosive limit of natural gas (methane)?

• A. 5%
• B. 1%
• C. 3%
• D. 7%

Answer: (A)

The lower explosive limit is the minimum concentration of a flammable gas in air that can sustain flame propagation if an ignition source is present. For methane, which is the primary component of natural gas, that threshold is about 5% by volume in air. Below this level, the mixture is too lean to ignite; above it, the mixture can ignite and potentially explode. So the correct value is 5% because it represents methane’s LEL. The other numbers are not the LEL: they’re either below the ignition threshold (too lean) or not the defining lower limit.

The lower explosive limit is the minimum concentration of a flammable gas in air that can sustain flame propagation if an ignition source is present. For methane, which is the primary component of natural gas, that threshold is about 5% by volume in air. Below this level, the mixture is too lean to ignite; above it, the mixture can ignite and potentially explode.

So the correct value is 5% because it represents methane’s LEL. The other numbers are not the LEL: they’re either below the ignition threshold (too lean) or not the defining lower limit.