What is the minimum temperature a substance must reach to ignite?

The minimum temperature a substance must reach to ignite is known as the ignition temperature. This specific temperature is critical because it indicates when a material will begin to combust without the need for an external flame or spark. Understanding ignition temperature is essential for fire safety and prevention, as knowing this value helps firefighters and safety personnel assess the risks associated with different materials in various conditions.

While there are other terms related to fire behavior and flammability, such as flash point and ignition point, these refer to different concepts. The flash point, for example, is the lowest temperature at which vapors of a combustible liquid can ignite when exposed to an open flame or spark but does not necessarily mean the material will continue to burn once ignited. Therefore, ignition temperature specifically represents the threshold for self-sustained combustion, making it the correct term in the context of the question.