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.
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Term
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Meaning
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Ignition Source Required?
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flash point
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lowest temperature at which the liquid will vaporize and form an ignitable mixture with air
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yes, repeatedly
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fire point
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temperature at which vapor will continue to burn once ignited
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yes
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autoignition temperature
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temperature at which a fire will occur without an ignition soucre
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no
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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
Significance:
(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.
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Flash Point
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Hazard
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> 93°C (> 200°F)
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very low
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66 to 93°C
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low to moderate
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38 to 66°C
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moderate to high
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-18 to 38°C
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high to extreme
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< -18°C (< 0°F)
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extreme
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