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Difference Between Combustible and Flammable Liquids

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 General Industry
Combustible liquids §1926.155(c) §1910.106(a)(18)
“[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 §1926.155(h) §1910.106(a)(19)
“[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?

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