Flammable liquids and gases with a flashpoint below 73 degrees F are covered by PSM if held in a single process at or above 10,000 pounds, without appearing on Appendix A. This category catches many facilities by surprise, particularly refineries, terminals, and chemical plants handling large inventories of gasoline, naphtha, LPG, or other light hydrocarbons. OSHA has issued significant guidance on what counts as flammable for PSM purposes, how to handle mixtures, and whether NFPA classifications align with OSHA's definition. These letters are essential reading for any facility handling bulk flammables.

What OSHA Has Said

Jun 28, 2019
Flammable Liquid Mixtures and PSM TQ Calculation
OSHA addresses how to determine threshold quantity applicability for mixtures of flammable liquids. The analysis focuses on the flash point of the mixture, not the individual components.
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Jun 4, 2018
LPG and Propane TQ Aggregation Across Multiple Spheres
OSHA clarifies how propane and LPG inventories are aggregated across a tank farm for PSM TQ purposes, reaffirming the connected-vessels doctrine in the context of flammables.
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Dec 19, 2018
Gasoline and Flammable Liquid Coverage at Fuel Terminals
OSHA evaluates PSM applicability at a petroleum product terminal handling large gasoline inventories and addresses the interaction between the retail exemption and the flammables TQ category.
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Sep 9, 1993
Original Guidance on Flammable Liquid Coverage and Flashpoint Definition
Early OSHA interpretation establishing how flammable liquid is defined for PSM purposes and confirming that OSHA's definition follows the Hazard Communication Standard, not necessarily NFPA classifications.
Read OSHA Letter ↗

⚡ Key Compliance Takeaway

Any process holding 10,000 or more lbs of a flammable liquid with flashpoint below 73 degrees F is covered. Run the numbers on all interconnected inventories. Gasoline, naphtha, pentane, LPG, and similar hydrocarbons frequently trigger coverage at terminals and refineries even when Appendix A chemicals are absent.