Subpart F
Approved means the equipment has been listed or approved by a nationally recognized testing laboratory or a federal agency that issues approvals for such equipment. For example, 1926.155(a) defines "approved" to include approvals from organizations like Underwriters' Laboratories or Federal agencies such as the U.S. Coast Guard.
A closed container is one sealed by a lid or other device so that neither liquid nor vapor will escape at ordinary temperatures. This is the exact definition found in 1926.155(b).
Combustion means any chemical process involving oxidation that produces light or heat. That is the definition provided in 1926.155(d).
A fire brigade is an organized group of employees who are knowledgeable, trained, and skilled in safely evacuating employees during emergencies and in assisting in firefighting operations. See the definition in 1926.155(e).
Fire resistance is defined as the ability of material or construction to resist fire so that, for a specified time and under standard heat conditions, it will not fail structurally or allow the side away from the fire to exceed a specified temperature. For this part, fire resistance is determined by the Standard Methods of Fire Tests of Building Construction and Materials, NFPA 251-1969, as stated in 1926.155(f).
Flammable means capable of being easily ignited, burning intensely, or having a rapid rate of flame spread. That is the plain-language definition in 1926.155(g).
A flammable liquid is any liquid with a vapor pressure at or below 40 psi (absolute) at 100 °F and a flash point at or below 199.4 °F; such liquids are divided into four categories by flashpoint and boiling point. The rule text in 1926.155(h) defines the categories, and the categories are:
Flash point is the temperature at which a liquid gives off enough vapor to form an ignitable mixture with air near the liquid surface or within the test vessel, and it must be determined by the appropriate, specified test procedure and apparatus in the standard. See the general definition in 1926.155(i). For the specific test methods that apply depending on viscosity and flashpoint, see 1926.155(i)(1) and 1926.155(i)(2).
Use the Tag Closed Tester (ASTM D-56) for liquids with viscosity less than 45 Saybolt Universal Seconds at 100 °F and with flashpoints below 175 °F. 1926.155(i)(1) specifies ASTM D-56-69 (incorporated by reference via 1926.6) or an equivalent method as defined by 1910.1200 appendix B.
Use the Pensky-Martens Closed Tester (ASTM D-93) for liquids having a viscosity of 45 Saybolt Universal Seconds or more at 175 °F (79.4 °C) or for liquids with higher viscosities, as specified in 1926.155(i)(2). The standard references ASTM D-93-69 via 1926.6 or allows equivalent methods per 1910.1200 appendix B.
Liquefied petroleum gases (LPG) or LP Gas are materials composed predominantly of hydrocarbons such as propane, propylene, butane (normal or iso-butane), and butylenes. This definition appears in 1926.155(j).
A portable tank is a closed container having a liquid capacity of more than 60 U.S. gallons and not intended for fixed installation. See the definition in 1926.155(k).
A safety can is an approved closed container of not more than 5 gallons capacity with a flash-arresting screen, a spring-closing lid and spout cover, and it must be designed to safely relieve internal pressure when subjected to fire exposure. This definition is in 1926.155(l).
Vapor pressure is the pressure (in pounds per square inch absolute) exerted by a volatile liquid, as determined by the "Standard Method of Test for Vapor Pressure of Petroleum Products (Reid Method)," ASTM D-323-58. See 1926.155(m) and the incorporation by reference via 1926.6.
"Flammable" is a general adjective meaning easily ignited or having a rapid flame spread, while "flammable liquid" is a defined class of liquids with specific numeric criteria: vapor pressure not exceeding 40 psi at 100 °F and flashpoint at or below 199.4 °F, subdivided into Categories 1–4 by flashpoint and boiling point. See the general adjective definition in 1926.155(g) and the defined classes in 1926.155(h).
Category 3 includes liquids with flashpoints at or above 73.4 °F (23 °C) and at or below 140 °F (60 °C); Category 4 includes flashpoints above 140 °F (60 °C) and at or below 199.4 °F (93 °C). See 1926.155(h)(3) and 1926.155(h)(4).
No — a liquid with vapor pressure greater than 40 psi (absolute) at 100 °F does not meet the 1926.155(h) definition of a flammable liquid, because that definition requires the liquid to have a vapor pressure not exceeding 40 psi at 100 °F and a flashpoint at or below 199.4 °F. See 1926.155(h).
Equivalent test methods are allowed when they are defined as equivalent by 1910.1200 appendix B; 1926.155(i)(1) and 1926.155(i)(2) reference ASTM D-56 and ASTM D-93 via 1926.6 but explicitly allow an equivalent method as defined in 1910.1200 appendix B.
No — a safety can as defined in 1926.155(l) must be an approved closed container of not more than 5 gallons capacity and include the specified safety features.
OSHA's June 6, 2024 interpretation explains that Category 1 flammable gases in on-site equipment at one location are aggregated toward the 10,000-pound PSM threshold when they are part of activities defined as a "process" (including storage and on-site movement). The letter clarifies that Category 1 flammable gases are subject to PSM when their aggregate weight on site in one location equals or exceeds 10,000 pounds. See the PSM interpretation P����SM flammable gas aggregation (June 6, 2024) and the PSM application in 29 CFR 1910.119.