The ignition temperature of a given substance is the measure of the minimum temperature at which the substance ignites, without the presence of an external spark or flame. Because of the fact that the material auto-ignites at this temperature range, it is also referred to as the substance's auto-ignition temperature.
The ignition temperature of a substance is a direct rating on the hazards which accompany it; substances that include ether and certain solvents, as just two examples, have low ignition temperatures and are easily ignited by just the radiant heat from sources as innocuous as steam pipes. According to Random House Dictionary, ignition temperature is the temperature at which a substance undergoes spontaneous combustion. Higher ignition temperature ranges are typically indications of a safer substance, in terms of ignition from temperature alone. However, these ranges are only guidelines. Under the right conditions, the ignition temperatures of various substances do change, and these changes are potentially significant.
The ignition temperature is of particular interest to engineers and to industry as a whole, because of the applications within environments where dust, gas and volatile liquids combine with high temperatures. Dust and gas accumulation are both prime concerns, since the right combination of these factors creates the potential for violent explosions.