OSHA Standard 29 CFR 1910.106 – Flammable and Combustible Liquids
The OSHA standard 29 CFR 1910.106 governs the handling, storage, and use of flammable and combustible liquids in the workplace. In simple terms, these are liquids that can burn, and they are classified as either flammable or combustible based on their flashpoints—the temperature at which they can ignite.
Flammable vs. Combustible Liquids
- Flammable liquids ignite and burn readily at normal working temperatures.
- Combustible liquids can also burn, but they require higher temperatures—usually above typical working conditions.
Flash Point Defined
The flash point of a liquid is the lowest temperature at which it emits enough vapor to form an ignitable mixture with air near its surface or within a container. This is determined using specific testing methods and apparatus.
Flammable Liquids:
- Have a flash point below 100°F (37.8°C)
- Examples:
- Ethyl ether
- Acetone
- Benzene
- Toluene
- Hydrazine and Styrene (flash points between 73°F and 100°F)
Combustible Liquids:
- Have a flash point at or above 100°F (37.8°C)
- Examples:
- Acetic acid
- Naphtha
- Cyclohexanol
- Formic acid
- Nitrobenzene (flash points between 100°F and 199°F)
Flammable Range
When the vapors of a flammable liquid mix with air in the right proportions and are exposed to an ignition source, rapid combustion or an explosion can occur. The flammable range represents the range of vapor concentrations in air that can ignite.
- Lower Flammable Limit (LFL): The minimum concentration of vapor in air below which a flame will not propagate when exposed to an ignition source.
- Upper Flammable Limit (UFL): The maximum concentration of vapor in air above which a flame cannot propagate.
These limits are typically expressed as percentages by volume of vapor in air. Combustion can only occur when the vapor concentration falls between the LFL and UFL, within the flammable range.