The explosive range of benzene is 1.4% to 8% by volume in air. If you sample an empty tank that had contained benzene and obtained a reading of 50% L.E.L. on a combustible gas indicator, then the __________.
• Meaning of L.E.L. (Lower Explosive Limit) and how it relates to the explosive range • How to convert a % of L.E.L. reading into an actual vapor concentration by volume • What it means for a mixture to be too lean, too rich, or within the flammable range
• If the explosive range is 1.4% to 8% by volume, what actual concentration in % by volume corresponds to 100% L.E.L.? • If the meter shows 50% L.E.L., what fraction of 1.4% is that, and what does that tell you about whether the mixture can burn? • Look carefully at each choice: does each one follow logically from a 50% L.E.L. reading, or is at least one statement not fully supported?
• Compute the actual % by volume that corresponds to 50% of the L.E.L. • Decide whether that value is below, within, or above the stated flammable (explosive) range of 1.4%–8% by volume • Check whether each option (A, B, C) must be true at 50% L.E.L., and only pick “all of the above” if every single statement is clearly supported
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