What does LEL stand for in gas detection terminology?

• A. Lower Explosive Limit
• B. Lower Emission Limit
• C. Local Explosive Level
• D. Light Emission Limit

Answer: (A)

Lower Explosive Limit is the minimum concentration of a flammable gas in air that can ignite if an ignition source is present. Mixtures leaner than this won’t ignite, while reaching or exceeding the LEL increases the fire risk. Gas detectors use a percentage of the LEL to standardize risk across different fuels, so a given gas concentration is interpreted relative to how close it is to the flammability limit. For example, methane has an LEL around 5% by volume in air, so 1% methane is 20% of its LEL. The other terms aren’t standard in gas-detection terminology, so they don’t describe flammability thresholds.