What is the term for ignition that occurs without any external source?

Autoignition refers to the process where a substance ignites spontaneously without any external flame, spark, or heat source. This phenomenon occurs when the temperature of the material reaches its ignition point due to factors such as compression or chemical reactions occurring within the substance itself.

Understanding autoignition is crucial for firefighters as it can lead to unexpected fire hazards, especially in environments where volatile substances are present. For example, materials like fuels can reach their autoignition temperature under certain conditions, leading to fires that cannot be predicted or controlled through traditional ignition sources.

Chemical ignition typically implies an ignition caused by a chemical reaction, but this does not encompass the broader scenario of spontaneous ignition without an external source. Piloted ignition refers to ignition that requires an external flame or spark to commence the combustion process, while manual ignition explicitly indicates that a person is involved in initiating the fire. These distinctions highlight why autoignition is the most accurate term for ignition that occurs without any external source.