Webster’s dictionary defines “combustible” as “capable of …a rapid chemical process … that produces heat and usually light”; and defines “flammable” as “capable of being easily ignited and of burning quickly.” In everyday language, there doesn’t seem to be much of a difference between the two terms. However, there is a significant difference in their meanings in the DOT’s Hazardous Materials Regulations (HMR). This can affect shipments of fuels, heating oils, and even high proof alcoholic beverages.
For the purposes of hazmat transportation, a flammable liquid is a liquid having a flash point of less than or equal to 140°F. A combustible liquid is a liquid that is NOT OTHERWISE HAZMAT (i.e., it doesn’t meet the criteria for any other hazard class) and has a flashpoint above 140°F and below 200°F. [173.120(a) and (b)]
Some flammable liquids ‒ those with flashpoints at or above 100°F ‒ may be reclassified as combustible liquids (for ground shipments only). Why is this important? Because this provision of the HMR provides great relief for some of the most common hazmat shipments. As a trainer, I am always surprised by how many hazmat shippers are unaware of the opportunities for relief found here. [49 CFR 173.150(f)]
Here’s how it works. Unless they are environmental hazards, the US Department of Transportation (DOT) excludes combustible liquids from most hazmat regulations. By environmental hazards, we mean marine pollutants, hazardous substances, and hazardous wastes as defined at 49 CFR 171.8.
If the material is not an environmental hazard, when shipped in non-bulk packagings, combustible liquids are NOT SUBJECT TO REGULATION AS HAZMAT! This means you can pack combustible liquids in drums, jerrycans, or other non-bulk packagings and not have to worry about hazmat labels or shipping papers or any other hazmat provision.
When shipped in bulk packagings, like cargo tanks, or in non-bulk packagings as environmental hazards, combustible liquids are only required to follow the communication rules for:
- Shipping papers,
- Packaging markings, including ID#s on bulk packagings, and
Hazard labels are not required.
Most significantly, UN tested and marked packagings are not required. You can use any kind of packaging as long as it meets the basic performance requirements of 49 CFR 173 Subpart B.
Be advised that while you can find similar exclusions in international and foreign regulations for flammable and combustible liquids, you must exercise caution as these exclusions do not always apply when shipping by air or sea. Check your ICAO Technical Instructions and IMDG Code regulations before proceeding.
Let’s look at a typical example of a combustible liquid ‒ the fuel truck delivering heating oil to your residential neighborhood. Number 2 fuel oil, commonly used to heat homes in the United States, has a flash point between 125°F and 200°F. This means the fuel truck (a bulk package) carrying #2 oil still needs shipping papers, an ID# on the cargo tank, and placards showing COMBUSTIBLE or FLAMMABLE Liquid. [49 CFR 172.504(f)] The driver of the vehicle needs a hazmat endorsement on their Commercial Driver’s License and the carrier needs to Register under 49 CFR 107 Subpart G. Beyond relaxed criteria for the cargo tank itself, there’s not much in the way of relief here.
On the other hand, when shipping 55-gallon drums of diesel fuel (typical flashpoint greater than 125°F) or jerrycans of kerosene (typical flashpoint above 110°F) on a flatbed truck, the diesel fuel and kerosene are not subject to regulation as hazmat. These flammable liquids are being shipped by ground in non-bulk packages and can be reclassified as combustible liquids. No shipping papers are required for transport, no hazard labels or ID#s are required on the containers, and no placards are required on the vehicle no matter how many containers are loaded.
If you’re eligible for this exclusion but not taking advantage of it, you might want to consider it. It can simplify your shipping operations for these materials and save your company money with the carrier.
Be advised that all applicable OSHA requirements for Hazard Communication [29 CFR 1910.1200] would continue to apply.
by James Griffin, CDGP