If there is too little vapor in the fuel-air mixture (the mixture is too lean), then ignition will not occur. This concentration is referred to as the ____.

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The lower explosive limit (LEL) represents the minimum concentration of vapor in the air required for ignition to occur. If the mixture is too lean, meaning there is not enough vapor present, then ignition cannot occur. The higher explosive limit (HEL) represents the maximum concentration of vapor in the air that can support combustion. The explosion point is not a commonly used term in reference to fuel-air mixtures, and the flashpoint refers to the temperature at which a liquid fuel gives off enough vapor to ignite.

If There Is Too Little Vapor in the Fuel-Air Mixture