OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

July 14, 2010

Letter # 20060425-7047

Re: The definitions of combustible and flammable liquids under 29 CFR 1926 and 29 CFR 1910.

Question #1: Why are the definitions for combustible liquids and flammable liquids different under OSHA's construction and general industry standards?

Answer #1:

The terms "combustible liquids" and "flammable liquids" are defined in the construction standard at 29 CFR 1926 and in the general industry standard at 29 CFR 1910 as follows:

Construction Standard Definitions
  Construction General Industry
Combustible liquids


"[A]ny liquid having a flash point at or above 140 °F. (60 °C.) and below 200 °F. (93.4 °C.)."


"[A]ny liquid having a flashpoint at or above 100 °F. (37.8 °C.)."

Flammable liquids


"[A]ny liquid having a flash point below 140 °F. and having a vapor pressure not exceeding 40 pounds per square inch (absolute) at 100 °F."


"[A]ny liquid having a flashpoint below 100 °F. (37.8 °C.), except any mixture having components with flashpoints of 100 °F. (37.8 °C.) or higher, the total of which make up 99 percent or more of the total volume of the mixture."

The definitions in the two standards are different because the definitions were adopted from different sources. The definitions in the general industry standard originated in a national consensus standard, NFPA 30-1969, while the definitions in the construction standard were adopted from established federal standards under the Construction Safety Act. Because the two sources defined the terms differently, the construction standard and the general industry standard are not consistent.

Question #2: Are there any plans to make the definitions consistent?

Answer #2:

OSHA is currently addressing these definitions in the Hazard Communication rulemaking. The proposed rule, available at 74 Federal Register 50280 (Sept. 30, 2009), proposes new definitions for combustible and flammable liquids that correspond with the Globally Harmonized System of Classification and Labeling of Chemicals (GHS). The proposed rule is available on the OSHA website at http://osha.gov/FedReg_osha_pdf/FED20090930.pdf.

If you need additional information, please contact us by fax at: U.S. Department of Labor, OSHA, Directorate of Construction, Office of Construction Standards and Guidance, fax #202-693-1689. You can also contact us by mail at the above office, Room N3468, 200 Constitution Avenue, N.W., Washington, D.C. 20210, although there will be a delay in our receiving correspondence by mail.



Bill Parsons, Acting Director
Directorate of Construction