What is the range of an LEL?

• A. 0 to 1%
• B. 0 to .6
• C. .7 to 5%
• D. More than 5 percent of

Answer: (B)

The lower explosive limit is the minimum percent by volume of flammable vapor in air that can sustain a flame if an ignition source is present. In safety basics, many common fuels have LEL values that lie at very low vapor concentrations, so the practical range you’ll see cited for the LEL is from 0% up to about 0.6% by volume. That’s why the best choice reflects a range starting at zero and extending only to around 0.6%. Higher ranges would imply ignition at much richer vapor–air mixtures, which isn’t what the LEL describes.