Both Flammable and Combustible Liquids are Class 3 hazardous materials defined and described by the US DOT at 49 CFR 173.120. Too often, this US DOT term is mistakenly used interchangeably with the US EPA term for describing a type of characteristic hazardous waste: Ignitable Liquid. Though similar in many respects, the terms originate from different Federal agencies and have differing determination criteria. The description of Flammable and Combustible Liquids as defined by US DOT is the purpose of this article. You may also read my article about the US EPA Determination of an Ignitable Liquid as a Hazardous Waste.
A Flammable Liquid, “means a liquid having a flash point of ≤60°C (140°F), or any material in a liquid phase with a flash point ≥37.8°C (100°F) that is intentionally heated and offered for transportation or transported at or above its flash point in a bulk packaging…”
So, to meet the US DOT definition of a Class 3 Flammable Liquid it must be…
- A liquid with a flash point of ≤60°C (140°F), or;
- Any material with a flash point ≥37.8°C (100°F), that is…
- Intentionally heated and offered for transportation, or;
- Transported at or above its flash point in a bulk packaging.
Even if matching the above description, the following materials are exempt from definition as a Flammable Liquid:
- Any liquid meeting one of the definitions of a Class 2 (Divisions 2.1, 2.2, & 2.3) compressed gas at 49 CFR 173.115.
- Any mixture having one or more components with a flash point ≥60°C (140°F), that make up at least 99% of the total volume of the mixture, if the mixture is not offered for transportation or transported at or above its flash point.
- Any liquid with a flash point >35°C (95°F) that does not sustain combustion according to ASTM D 2406 (IBR, see §171.7 of this subchapter) or the procedure in appendix H of this part.
- Any liquid with a flash point >35°C (95°F) and with a fire point >100°C (212°F) according to ISO 2592 (IBR, see §171.7 of this subchapter).
- Any liquid with a flash point >35°C (95°F) which is in a water-miscible solution with a water content of more than 90% by mass.
A Combustible Liquid, “means any liquid that does not meet the definition of any other hazard class specified in this subchapter and has a flash point >60°C (140°F) and <93°C (200°F).”
So, to meet the US DOT definition of a Class 3 Combustible Liquid it must…
- Not meet the definition of any other US DOT hazard class, and;
- Be a liquid with a flash point >60°C (140°F) and <93°C (200°F).
In some cases, the US DOT will allow you to reclassify a Flammable Liquid as a Combustible Liquid to take advantage of the reduced regulatory burden when transporting Combustible Liquids.
Flammable Liquids…Combustible Liquids…Ignitable Liquids…It’s up to you to keep them straight and to determine if you are subject to their unique regulations when handling or transporting them. My training – either public workshop or on-site – will teach you and your employees what they need to know to perform their jobs in compliance with the regulations. Contact me to discuss your training needs and which option will work the best for you.