What term is defined as the lowest temperature at which a combustible material ignites in air without a spark or flame?

What term is defined as the lowest temperature at which a combustible material ignites in air without a spark or flame?

• A. Auto Ignition Temperature
• B. Fire Point
• C. Flash Point
• D. Ignition Temperature

Answer: (A)

Autoignition temperature is the temperature at which a material will ignite in air without any external ignition source, such as a spark or flame. At this temperature, the material’s own thermal energy drives a reaction with oxygen fast enough to start combustion spontaneously. This distinguishes it from the flash point, where vapors can form an ignitable mixture but still require an external flame or spark to ignite; and the fire point, where the flame will be sustained once ignition has occurred. The term ignition temperature is sometimes used ambiguously, but the definition given—ignition without an external source—points to autoignition temperature.

Autoignition temperature is the temperature at which a material will ignite in air without any external ignition source, such as a spark or flame. At this temperature, the material’s own thermal energy drives a reaction with oxygen fast enough to start combustion spontaneously. This distinguishes it from the flash point, where vapors can form an ignitable mixture but still require an external flame or spark to ignite; and the fire point, where the flame will be sustained once ignition has occurred. The term ignition temperature is sometimes used ambiguously, but the definition given—ignition without an external source—points to autoignition temperature.