What are Lower Explosive Limits?

Lower Explosive Limits (LEL) refer specifically to the minimum concentration of vapors or gases in the air that is necessary for combustion to occur when exposed to an ignition source. This threshold is crucial for safety in environments where flammable substances are present, as it defines a point below which the mixture is too lean to ignite. Understanding LEL is vital for ensuring appropriate safety measures are in place to prevent fires or explosions in various settings, such as industrial or laboratory environments.

This concept is fundamental in processes involving flammable materials, as working with concentrations below the lower explosive limit means that no ignition can happen, regardless of the presence of an ignition source. The other options inaccurately describe LEL: they either refer to maximum concentrations or safety levels, which do not accurately capture the specific definition of Lower Explosive Limits.