The Lower Explosive Limit (LEL) describes the minimum vapor concentration in air that will:

The Lower Explosive Limit (LEL) describes the minimum vapor concentration in air that will:

• A. ignite and burn.
• B. ignite momentarily but not sustain.
• C. condense.
• D. cause corrosion.

Answer: (A)

The lower explosive limit is the lowest vapor-to-air ratio that can ignite and burn if an ignition source is present. Below this limit, the mixture is too lean to sustain a flame. That’s why the option describing ignition and burning at least as a minimum concentration best fits. In the flammable range, which lies between the LEL and the upper explosive limit, ignition can propagate and a flame can be sustained. The other ideas don’t fit: condensing is about a phase change rather than ignition, corrosion is about chemical damage to materials, and “ignite momentarily but not sustain” doesn’t capture the threshold at which a flammable mixture can burn continuously.

The lower explosive limit is the lowest vapor-to-air ratio that can ignite and burn if an ignition source is present. Below this limit, the mixture is too lean to sustain a flame. That’s why the option describing ignition and burning at least as a minimum concentration best fits. In the flammable range, which lies between the LEL and the upper explosive limit, ignition can propagate and a flame can be sustained. The other ideas don’t fit: condensing is about a phase change rather than ignition, corrosion is about chemical damage to materials, and “ignite momentarily but not sustain” doesn’t capture the threshold at which a flammable mixture can burn continuously.