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Classifications of OSHA Flammables

The Occupational Safety and Health Administration of the U.S. Department of Labor (OSHA) classifies flammable chemical hazards in four broad categories, based on degree of flammability. Specific OSHA regulation standards are found in part 29 of the Code of Federal Regulations (CFR). OSHA flammability standards apply to aerosol, gas, liquid and solid materials.

  1. OSHA Aerosol Flammables

    • OSHA standard number 29 CFR 1910.1200 (c) defines a flammable aerosol as "an aerosol that, when tested by the method described in 16 CFR 1500.45, yields a flame projection exceeding 18 inches at full valve opening, or a flashback (a flame extending back to the valve) at any degree of valve opening." Under the definition of aerosol found in OSHA standard 1910.106(a)(1), aerosol is a mist, spray or foam dispensed from its container under pressure.

    OSHA Gas Flammables

    • A gas is classified as flammable by OSHA based on its percent of concentration in air. When a gas at ambient temperature and pressure forms a flammable mixture with air at a concentration of 13 percent by volume or less, it is a flammable gas. Under OSHA standard 1910.12(c)(B), a gas is also considered flammable when it forms a range of flammable mixtures "with air wider than 12 percent by volume, regardless of the lower limit."

    OSHA Liquid Flammables

    • A flammable liquid is any liquid with a flashpoint below 100 degrees Fahrenheit (37.8 degrees Celsius). Flammable liquids are known as Class I liquids, which are divided into class IA, IB, and IC. Class IA liquids have flashpoints below 73 degrees Fahrenheit and boiling points below 100 degrees Fahrenheit, such as acetaldehyde and ethyl ether. Class IB materials have the same flashpoint level as IA and a boiling point above 100 degrees Fahrenheit. Examples include acetone and benzene. Class IC includes styrene and turpentine, with flashpoints above 73 degrees Fahrenheit and below 100 degrees Fahrenheit.

    OSHA Solid Flammables

    • A solid flammable is likely to cause fire through friction, spontaneous chemical change, absorption of moisture, or retained heat. According to OSHA flammable standard 1910.1200(c)(iv), a solid is also flammable if it "can be ignited readily and when ignited burns so vigorously and persistently as to create a serious hazard." Magnesium metal and sodium metal are two items classified as water-reactive flammable solids by OSHA.

    OSHA Combustibles

    • The cutoff point for OSHA-flammable classifications is the 100-degree Fahrenheit flashpoint. A chemical with a flashpoint above 100 degrees Fahrenheit is a combustible based on the OSHA definition standard 1910.106(a)(18). Flammables also do not include explosives or blasting agents, which are subject to other OSHA classifications.

    OSHA explosives

    • Flammables also do not include explosives or blasting agents, which are subject to other OSHA classifications. An explosive is designed to function "with substantially instantaneous release of gas and heat," according to OSHA's explosive definition, OSHA standard 1910.109(a)(3).

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