How is autoignition temperature defined?

Autoignition temperature is defined as the lowest temperature at which a combustible material will ignite spontaneously, without the need for an external ignition source such as a spark or flame. This concept is crucial in fire investigations, as it helps understand the conditions under which various materials can catch fire on their own due to heat accumulation or external factors like ambient temperature.

Choosing this option correctly highlights the significance of autoignition temperature in assessing fire hazards. For example, certain chemicals or fuels have relatively low autoignition temperatures, which means they can ignite from heat generated through friction, chemical reactions, or even high ambient temperatures, necessitating careful handling and storage procedures.

Other options, while related to combustion and ignition in some way, do not accurately describe autoignition temperature. Understanding these definitions and their correct applications can significantly impact fire safety practices and investigations.