Main Page | See live article | Alphabetical index A substance's autoignition temperature is the lowest temperature at which it will burst into flame in air, even without an external spark or other source of ignition. The lowest temperature at which a substance will ignite in the presence of an external source of ignition is its flash point. Autoignition temperatures are measured using the same closed cup apparatus used for measuring flash points. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.