Question 37Safety & Environmental - Assistant Engineer

The correct answer is B) 5 percent methane by volume will give a reading of 100 percent L.E.L. on a combustible gas indicator. This is because the explosive range of methane is 5% to 15% by volume in air. At 5% methane by volume, the mixture is at the lower explosive limit (L.E.L.), meaning it is the minimum concentration of methane needed to sustain an explosion. A combustible gas indicator would read 100% L.E.L. at this concentration. The other options are incorrect because: A) 3% is below the L.E.L., C) 10% is within the explosive range but not at the L.E.L., and D) 20% is above the upper explosive limit and is too lean to burn.