What is the term for the heating of a fuel to the point where it ignites without an external ignition source?

The term for the heating of a fuel to the point where it ignites without an external ignition source is known as autoignition. This process occurs when a material reaches its ignition temperature due to the heat generated from compression, chemical reactions, or prolonged exposure to heat, without the need for a spark or flame.

Autoignition is significant in fire investigations as it helps in understanding the conditions that led to a fire, especially in situations where there might not be any discernible source of ignition. It is also distinct from combustion, which refers to the overall chemical reaction of burning, and flashover, which is a rapid spread of fire in a confined space. Spontaneous ignition, while similar to autoignition, typically refers to situations where materials ignite without external ignition sources due to chemical changes or self-heating over time.