Tankerman · Gas Hazards — Flammable Range
A hydrocarbon vapor mixture will NOT burn when it is:
- AAt exactly the lower flammable limit
- BExactly stoichiometric
- CAbove the upper flammable limit (too rich)✓ Correct
- DAt the flash point
Explanation
Above the upper flammable limit (UFL) the mixture is too rich (insufficient oxygen) to ignite; below the lower flammable limit (LFL) it is too lean. Only between LFL and UFL is it flammable.
Authority: ISGOTT (flammability)
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