The Flammable Liquids Standard Defined

By Ana Ellington, BLR Legal Editor

Flammable liquids are present in nearly every workplace. Gasoline, diesel fuel, and many common products like solvents, thinners, cleaners, adhesives, paints, and polishes can be flammable—they are part of our everyday life. However, if these liquids are used or stored improperly, it could present serious hazards that could result in injuries and even death.

The flammable liquids standard (29 CFR 1910.106) was revised in 2012, in response to U.S. OSHA’s revising the Hazard Communication standard to incorporate the Globally Harmonized System (GHS).

The standard’s title was changed from “Flammable and Combustible Liquids” to “Flammable Liquids.” One significant change is that the revised regulation lists liquids as “categories” rather than “classes.”

Defining Flammables

To understand OSHA requirements for the safe storage of flammables, we must define flammable liquid. The flashpoint and boiling point determine the category of a liquid.

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OSHA defines a flammable liquid as any liquid having a flashpoint at or below 199.4°F (93°C). Flammable liquids are divided into four categories:

• Category 1: Liquids with flashpoints below 73.4°F (23°C) and boiling point at or below 95°F (35°C) (1910.106(a)(19)(i)). Examples: acetaldehyde and ethyl ether.
• Category 2: Liquids with flashpoints below 73.4°F (23°C) and boiling points at or above 95°F (35°C) (1910.106(a)(19)(ii)). Examples: acetone, benzene, and toluene.
• Category 3: Liquids with flashpoints at or above 73.4°F (23°C) and at or below 140°F (60°C). When a Category 3 liquid with a flashpoint at or above 100°F (37.8°C) is heated for use to within 30°F (16.7°C) of its flashpoint, it must be handled as a Category 3 liquid with a flashpoint below 100°F (37.8 °C) (1910.106(a)(19)(iii)).
• Category 4: Includes liquids having flashpoints above 140°F (60°C) and at or below 199.4°F (93°C). When a Category 4 flammable liquid is heated for use to within 30°F (16.7°C) of its flashpoint, it must be handled as a Category 3 liquid with a flashpoint at or above 100°F (37.8°C) (1910.106(a)(19)(iv)).

(Note: The term combustible liquid is no longer considered a class or category in the revised standard.)

Whether liquids are Category 1 or 4 is not the only factor you should consider when determining your safe storage needs. You also need to consider ignition temperature, explosive limits (LEL or UEL), vapor pressure, specific gravity, and vapor density if you want to design a truly safe storage system.

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Safety Cans

One technique to reduce the hazards associated with flammables is the use of safety cans. OSHA defines a safety can as “an approved container, of not more than 5 gallons capacity, having a spring-closing lid and spout cover and so designed that it will safely relieve internal pressure when subjected to fire exposure” (29 CFR 1910.106(a)(29)).

The standard limits the amount of liquid in a single safety can and other portable containers.

Container type	Category 1	Category 2	Category 3	Category 4
Glass or approved plastic	1 pint	1 quart	1 gallon	1 gallon
Metal (other than DOT drums)	1 gallon	5 gallon	5 gallon	5 gallon
Safety cans	2 gallon	5 gallon	5 gallon	5 gallon
Metal drum (DOT spec.)	60 gallon	60 gallon	60 gallon	60 gallon
Approved portable tanks	660 gallon	660 gallon	660 gallon	660 gallon