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Classification of flammable and combustible liquids
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The following tool guideline is originally published in the Complete Guide to Laboratory Safety, Third Edition by Terry Jo Gile. Click here for more information.
According to OSHA 1910.106(a)(19) , a flammable liquid means any liquid having a flash point below 100ºF (37.8ºC), except mixtures with flash points of 100ºF or higher, the total of which makes up 99% or more of the mixture.
Flammable liquids are divided into three classes:
| |
Flash Point |
Boiling Point |
Examples |
| Class 1A |
Below 73ºF (22.8ºC) |
Below 100ºF (37.8ºC) |
Acetaldehyde, ethyl ether, pentane |
| Class 1B |
Below 73ºF (22.8ºC) |
At or above 100ºF (37.8ºC) |
Acetone, gasoline, benzene |
| Class 1C |
At or above 73ºF (22.8ºC) |
Below 100ºF (37.8ºC) |
Turpentine, xylene, isopropanol |
A combustible liquid refers to any liquid with a flash point at or above 100ºF (37.8ºC), according to OSHA 1910.106(a)(18).
Combustible liquids are divided into two classes:
| |
Flash Point |
Examples |
| Class II |
At or above 100ºF (37.8ºC) and below 140ºF (60ºC),
except any mixture having components with flashpoints
of 200ºF (93.3ºC) or higher, the volume of
which make up 99% or more of the total volume of
the mixture |
Acetic acid, cyclohexane |
| Class III |
At or above 140ºF (60ºC) |
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| Class IIIA |
At or above 140ºF (60ºC) and below 200ºF (93.3ºC),
except any mixture having components with flash
points of 200ºF (93.3ºC) or higher, the volume of
which makes up 99% or more of the total volume of
the mixture |
Formic acid and cyclohexanol |
| Class IIIB |
At or above 200ºF (93.3ºC) |
Formalin and picric acid |
* When a combustible liquid is heated for use to within 30ºF (16.7ºC) of its flash point, it shall be handled in accordance with the requirements for the next lower class of liquids, according to 1910.106(a)(18)(iii).
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