Combustion autoignition point

Applies to all other combustible substances. Open flame includes hot surfaces with a temperature above the autoignition point of the substeince. 

The combustion characteristics of liquid fuels are similarly determined by measures of their ability to sustain a flame. Two measures of the combustion characteristics of liquid fuels especially related to safety are flash point and autoignition temperature. The flash point is the maximum temperature at which a liquid fuel can be maintained in an open vessel exposed to air before which it will sustain a flame... 

A third approach has been suggested by Jaroudi (Jl), who points out that one necessary condition to prevent reignition of the propellant is to ensure that the gas temperature resulting from thermal equilibrium between the injected fluid and the combustion products is below the propellant autoignition temperature. This approach leads to the conclusion that the ratio of coolant mass flow to propellant mass flow is the critical correlating parameter. 

Flashpoints (the reason for the plurality is explained in paragraph 1.3) have the advantage of being linked to the boiling point, the pressure and the lower explosive limit. This is the reason why flashpoints are such important parameters in the evaluation of the inflammability risk of a liquid or a solid. The measurement of flashpoints implies the existence of an ignition flame for the gaseous mixture. Nevertheless, contact of a suitable substance-air mixture with a hot surface can be sufficient to start the combustion of the mixture. The autoignition temperature is the parameter that determines the possibility that an inflammable material will combust in contact with a hot substance without the presence of a flame. 

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