Flash-point

noun
1.
Also, flashing point. Physical Chemistry. the lowest temperature at which a liquid in a specified apparatus will give off sufficient vapor to ignite momentarily on application of a flame.
2.
a critical point or stage at which something or someone suddenly causes or creates some significant action:
A 10 percent drop in mortgage rates will produce a flash point in the housing market.
3.
a critical situation or area having the potential of erupting in sudden violence:
The Mideast has been the flash point for a series of conflicts.
noun
1.
the lowest temperature at which the vapour above a liquid can be ignited in air
2.
a critical moment beyond which a situation will inevitably erupt into violence: the political mood has reached flash point
flash point
The lowest temperature at which the vapor of a flammable liquid will ignite in air. The flash point is generally lower than the temperature needed for the liquid itself to ignite.

For a given flammable substance, the lowest temperature at which vapors passing from the substance into the air will catch fire spontaneously if a small flame is present.

noun phrase

The place or time when something ”takes fire,” becomes exciting and exemplary: We want the White House to function as a flash point for whatever’s great in this couintry

[1990s+; in the technical sense, ”lowest point of ignition of a fluid, compound, etc,” the term is found by the 1870s]