Above the Upper Explosive Limit, the proportion of vapor in the mixture is too high to ignite and burn; the mixture is 'too rich'.

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Multiple Choice

Above the Upper Explosive Limit, the proportion of vapor in the mixture is too high to ignite and burn; the mixture is 'too rich'.

Understanding flammable limits helps you see when a fuel‑air mixture can ignite. The mixture will burn only if the vapor concentration sits between the lower explosive limit and the upper explosive limit. When the vapor concentration goes above the upper limit, there’s too much fuel relative to oxygen, so the mixture is too rich to sustain a flame. In that state, ignition cannot be supported even though the gas is flammable within the proper range. The other statements either describe ignition in imprecise terms, claim ignition becomes easier with more vapor (which isn’t true past the upper limit), or misstate that this range only exists at low pressure.

Understanding flammable limits helps you see when a fuel‑air mixture can ignite. The mixture will burn only if the vapor concentration sits between the lower explosive limit and the upper explosive limit. When the vapor concentration goes above the upper limit, there’s too much fuel relative to oxygen, so the mixture is too rich to sustain a flame. In that state, ignition cannot be supported even though the gas is flammable within the proper range. The other statements either describe ignition in imprecise terms, claim ignition becomes easier with more vapor (which isn’t true past the upper limit), or misstate that this range only exists at low pressure.

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