Lower Explosive Limits (LEL) define:

Lower Explosive Limits (LEL) define:

• A. The minimum concentrations for ignition of a flammable gas or vapor
• B. The maximum concentrations for ignition of a flammable gas or vapor
• C. The oxygen percentage at which ignition occurs
• D. Minimum concentrations for a flammable gas or vapor to ignite

Answer: (D)

LEL tells you the minimum concentration of a flammable gas or vapor in air that can ignite and sustain a flame when an ignition source is present. It marks the lower boundary of the flammable range; below this level, the mixture is too lean to burn. It’s usually expressed as a percent by volume in air and is used alongside the upper explosive limit to define where ignition is possible. The correct idea is that LEL corresponds to the minimum concentration required for ignition in air. The other concepts describe the upper limit or the need for oxygen, which are not what LEL measures.

LEL tells you the minimum concentration of a flammable gas or vapor in air that can ignite and sustain a flame when an ignition source is present. It marks the lower boundary of the flammable range; below this level, the mixture is too lean to burn. It’s usually expressed as a percent by volume in air and is used alongside the upper explosive limit to define where ignition is possible. The correct idea is that LEL corresponds to the minimum concentration required for ignition in air. The other concepts describe the upper limit or the need for oxygen, which are not what LEL measures.