Definition
The lowest temperature at which a flammable liquid gives off enough vapor to form an ignitable mixture with air near its surface. At the flash point, the vapor will briefly ignite if exposed to an open flame or spark, but it will not yet sustain continuous burning.
Plain English
The temperature at which a liquid like fuel or oil starts giving off enough fumes to catch fire from a spark, even though the liquid itself is not yet hot enough to keep burning on its own.
Context Anchor
Seen in fuel handling, aircraft maintenance, and fire-safety discussions, especially when comparing aviation gasoline and jet fuel.
Derivation
From 'flash,' meaning a sudden, brief burst of flame, and 'point,' meaning a specific value on a scale. The name describes exactly what happens: at this temperature, the vapor flashes when ignited, then goes out.
Why Pilots Care
A low flash point signals higher fire risk during fuel storage and transfer, directly affecting ramp safety decisions.
Grounding Statement
At the flash point, the air just above the liquid can become flammable even though the liquid may not look like it is doing anything.
Intuition Check
Do not assume flash point means the liquid itself is already burning. It means the liquid is warm enough to give off vapors that can flare up if an ignition source is present.
Example Sentence 1
Jet A has a relatively high flash point, which is one reason it is considered safer to handle than aviation gasoline.
Example Sentence 2
Knowing the flash point helped the crew decide where to store the fuel drums away from heat sources.