If diesel fuel vapors in a compartment are considered to be within the flammable range __________.

Correct Answer: Option B — an explosion may occur if a source of ignition is present

The flammable range exists between the Lower Explosive Limit (L.E.L.) and the Upper Explosive Limit (U.E.L.). When a vapor concentration falls within these bounds, the mixture is capable of supporting combustion. If an ignition source is introduced, the rapid oxidation will result in an explosion or fire.