What is the lower explosive limit for petroleum vapors?

What is the lower explosive limit for petroleum vapors?

• A. The point at which a vapor mixture ignites
• B. The point at which a vapor mixture does not ignite because it's too lean
• C. The point at which a vapor mixture ignites at high concentration
• D. The point at which a vapor mixture ignites only in the presence of water

Answer: (C)

The lower explosive limit is the minimum concentration of petroleum vapors in air that can support combustion if an ignition source is present. Below this level, the mixture is too lean to ignite because there isn’t enough fuel relative to the amount of air. For petroleum vapors, ignition can only occur when the vapor concentration is between the lower and upper explosive limits; the description of igniting at high concentration corresponds to the upper limit, not the lower. The option about ignition only in the presence of water isn’t related to flammable-range limits.

The lower explosive limit is the minimum concentration of petroleum vapors in air that can support combustion if an ignition source is present. Below this level, the mixture is too lean to ignite because there isn’t enough fuel relative to the amount of air. For petroleum vapors, ignition can only occur when the vapor concentration is between the lower and upper explosive limits; the description of igniting at high concentration corresponds to the upper limit, not the lower. The option about ignition only in the presence of water isn’t related to flammable-range limits.