OSHA #511 Occupational Safety and Health Standards for General Industry course

What does the term Lower Explosive Limit (LEL) refer to?

1. The maximum concentration of gas that can be safely inhaled

2. The lowest concentration of gas or vapor in air that can be ignited

3. The minimum temperature required for combustion

4. The highest pressure of vapor that can be contained

The correct answer is: The lowest concentration of gas or vapor in air that can be ignited

The term Lower Explosive Limit (LEL) refers to the lowest concentration of gas or vapor in the air that can ignite and support combustion when an ignition source is present. Understanding LEL is crucial for safety in workplaces where flammable substances are handled, as it helps in assessing the potential risks of fire and explosion in the environment. Monitoring LEL can assist employers in implementing safety measures to prevent the formation of ignitable mixtures in the air, thereby protecting workers from hazardous conditions. In this context, the other options do not accurately define LEL. The statement about the maximum concentration of gas that can be safely inhaled pertains to occupational exposure limits rather than explosive properties. The mention of the minimum temperature required for combustion relates to the flash point, which is a different safety consideration. Lastly, the highest pressure of vapor that can be contained does not describe LEL but speaks to pressure limits and vessel integrity instead. Thus, the answer that accurately captures the meaning of LEL is the one identifying it as the lowest concentration of gas or vapor that can ignite in the presence of an ignition source.