Flash point, fire point and autoignition temperature are three temperatures that describe how a flammable liquid is affected by temperature.


Normally the autoignition temperature is greater than the fire point which is greater than the flash point.




Ignition Source Required?

flash point

lowest temperature at which the liquid will vaporize and form an ignitable mixture with air

yes, repeatedly

fire point

temperature at which vapor will continue to burn once ignited


autoignition temperature

temperature at which a fire will occur without an ignition soucre



Each of these temperatures is affected by:

(1) the amount of oxygen present

(2) the presence of other flammable liquids

(3) the presence of flame retardants

(4) atmospheric pressure



(1) The lower the flash point the greater the hazard.

(2) At a high enough temperature even a flammable liquid of low hazard can burn.


Flash Point


> 93°C (> 200°F)

very low

66 to 93°C

low to moderate

38 to 66°C

moderate to high

-18 to 38°C

high to extreme

< -18°C (< 0°F)



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