Definition - What does Autoignition Temperature mean?
The autoignition temperature of a substance indicates the lowest temperature at which it may spontaneously ignite without the presence of an ignition source such as a flame or spark. At the auto-ignition temperature, the temperature alone provides sufficient energy to induce combustion. As the oxygen content of the ambient atmosphere increases, the auto-ignition temperature will decrease and increased pressure also decreases the temperature at which auto ignition can take place.
Safeopedia explains Autoignition Temperature
The auto ignition temperatures of various substances vary widely. For example, Triethylborane can ignite spontaneously at temperatures from -4F, while light hydrocarbons require a temperature of 1,202 F before they become spontaneously ignitable. The danger of autoignition hazards depends upon the type of industrial process and the chemicals used. For example, petroleum based hydraulic fluids can automatically ignite at 500 to 750 F. If operating temperatures exceed the lower limit, auto ignition may occur.