Autoignition temperature

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The autoignition temperature of a substance is the lowest temperature at which a chemical will spontaneously combust in a normal atmosphere, without an external source of ignition, such as a flame or spark. This temperature is required to supply the activation energy needed for combustion. The temperature at which a chemical will detonate decreases as the pressure increases or oxygen concentration increases. The lowest temperature at which a substance will ignite in the presence of an external source of ignition is known as its flash point.

Autoignition temperatures are measured using the same closed cup apparatus used for measuring flash points.

The autoignition temperature of paper, 451 °F (233 °C), is well known because of the popular novel Fahrenheit 451 by author Ray Bradbury.

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