The flash point is the lowest temperature at which a liquid under specified test conditions gives off flammable gas or flammable vapor in such an amount that upon contact with an effective ignition source immediately a flame occurs. Because the resulting heat of combustion is not sufficient to heat the liquid until it reaches the focal point, the combustion at the flash point comes back to a standstill even when the ignition source is not removed. The inflowing from the fuel vapor amount is also not sufficient to allow a permanent combustion.
At the same gas pressure, a few degrees above the flash point, is the firing point. From this temperature, a permanent combustion is possible even after removal of the ignition source, because the substance surface then delivers flammable vapors in sufficient quantity. Flash and firing point have to be distinguished from the ignition point.
The ignition point (also ignition temperature, spontaneous ignition temperature) defines the temperature to which one has to heat a substance or a contact surface, so that a combustible substance (solids, liquids, their vapor or gas) in the presence of air exclusively on the basis of its own temperature self-ignites - without an ignition source such as a spark.
Under safety aspects the flash point is in comparison to the firing point of far greater importance or relevance, since it defines the lowest temperature where at the inflammation of an explosive gas / air mixtures is possible.