Autoignition temperature

The autoignition temperature or self-ignition temperature, often called spontaneous ignition temperature or minimum ignition temperature (or shortly ignition temperature) and formerly also known as kindling point, of a <a href="/facts/Chemical_substance/EWcXU41d">substance</a> is the lowest <a href="/facts/Temperature/QyGe4gmj">temperature</a> at which it <a href="/facts/Spontaneous_combustion/ULScfFt1">spontaneously ignites</a> in a normal atmosphere without an external source of ignition, such as a <a href="/facts/Flame/ucMuoqa2">flame</a> or <a href="/facts/Spark_(fire)/BwGFWEtJ">spark</a>. This temperature is required to supply the <a href="/facts/Activation_energy/GqkgPvo0">activation energy</a> needed for <a href="/facts/Combustion/ohQoWj8z">combustion</a>. The temperature at which a chemical ignites decreases as the <a href="/facts/Pressure/eyc37GRG">pressure</a> is decreased. 

<ul><li>Substances which spontaneously ignite in a normal atmosphere at naturally ambient temperatures are termed <a href="/facts/Pyrophoricity/1b8Sl2AJ">pyrophoric</a>.</li></ul>
Autoignition temperatures of liquid chemicals are typically measured using a 500-millilitre (18 imp fl oz; 17 US fl oz) flask placed in a temperature-controlled oven in accordance with the procedure described in <a href="/facts/ASTM_International/xzdCexYJ">ASTM</a> E659.
When measured for <a href="/facts/Plastics/Kla5QItn">plastics</a>, autoignition temperature can also be measured under elevated pressure and at 100% oxygen concentration. The resulting value is used as a predictor of viability for high-oxygen service. The main testing standard for this is ASTM G72.

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Autoignition temperature