Every IBC tank manufactured for the transport of hazardous and non-hazardous goods carries a United Nations performance marking -- a coded string of letters and numbers stamped or embossed on the container. These markings are not decorative. They are a legally required certification that the container has passed rigorous testing and meets international safety standards for transport. If you ship, store, or receive liquids in IBC tanks, understanding these codes is essential to staying compliant and safe.
This guide breaks down the UN marking system character by character, explains the most common IBC rating codes, and covers the compliance implications for businesses in Nebraska and beyond. For a more hands-on reference, check our IBC data plate decoder guide that covers all markings on the tank, not just the UN code.
What Are UN Ratings?
The United Nations Committee of Experts on the Transport of Dangerous Goods developed a universal packaging classification system that applies to all containers used for transporting hazardous materials -- including IBC tanks. This system is codified in the UN Recommendations on the Transport of Dangerous Goods, commonly known as the "Orange Book." In the United States, these standards are adopted into law through the Department of Transportation's 49 CFR regulations.
A UN rating tells you four critical things about an IBC: what type of container it is, what material it is made from, whether it is rigid or flexible, and what level of hazard it is certified to contain. Every manufacturer must have their IBC designs tested and certified by an approved third-party testing laboratory before applying UN markings.
The UN Code Structure: Character by Character
A typical UN marking on a composite IBC tank looks like this: UN 31HA1/Y/[date]/[country]/[manufacturer]. Let us break down what each part means.
Position 1-2: Container Category (31)
The first two digits identify the type of container. For IBCs, the relevant codes are:
- 11 -- Rigid IBC, for solids, loaded or discharged by gravity
- 13 -- Flexible IBC, for solids
- 21 -- Rigid IBC, for solids, loaded or discharged under pressure
- 31 -- Rigid IBC, for liquids (this is the most common for standard IBC totes)
The vast majority of composite IBC totes you encounter in commercial use start with 31, indicating a rigid container designed for liquid transport.
Position 3: Material Code (H)
The letter in the third position identifies the material of construction:
- A -- Steel
- B -- Aluminum
- C -- Natural wood
- D -- Plywood
- F -- Reconstituted wood
- G -- Fiberboard
- H -- Plastic
- L -- Textile
- M -- Paper, multiwall
- N -- Metal (other than steel or aluminum)
Standard composite IBC tanks use H for the plastic (HDPE) inner bottle.
Position 4: Sub-Category (A or H)
The fourth character further specifies the construction:
- HA -- Composite IBC with a rigid plastic inner receptacle and a steel outer cage. This is the standard composite IBC tote you see everywhere.
- HH -- Composite IBC with a rigid plastic inner receptacle and a rigid plastic outer body (no steel cage). Less common, typically used for lighter-duty applications.
Position 5: Design Variant (1 or 2)
The final digit indicates whether the IBC has a bottom discharge:
- 1 -- With bottom discharge valve (standard for most IBC totes)
- 2 -- Without bottom discharge valve
Most Common UN Codes You Will See
UN 31HA1
Rigid composite IBC for liquids, plastic inner bottle with steel outer cage, with bottom discharge. This is the industry standard. Virtually every 275-gallon and 330-gallon composite IBC tote from Schutz, Mauser, and Greif carries this designation.
UN 31HH1
Rigid composite IBC for liquids, plastic inner bottle with plastic outer body, with bottom discharge. Found on all-plastic IBCs that do not have a steel cage. These are lighter and less expensive but cannot be stacked as heavily.
UN 31HA2
Same as 31HA1 but without a bottom discharge valve. Less common in commercial use. Top-discharge-only IBCs are used in applications where a bottom valve is a leak risk or contamination concern.
UN 31A
All-steel rigid IBC for liquids. Found on stainless steel and carbon steel IBCs used for flammable liquids, high-temperature applications, and aggressive chemicals that would attack plastic.
The Packing Group Letter: X, Y, or Z
After the container type code, you will see a letter that indicates the packing group -- the level of hazard the container is rated to hold:
- X -- Packing Group I, II, or III. This is the highest rating. The IBC can transport the most dangerous goods (high danger). IBCs rated X can also hold Packing Group II and III substances.
- Y -- Packing Group II or III. Medium danger rating. This is the most common rating for composite HDPE IBCs. A Y-rated IBC can transport moderately hazardous and low-hazard liquids.
- Z -- Packing Group III only. Low danger. The IBC is certified only for the least hazardous substances.
For non-hazardous goods like water, food products, and mild chemicals, any packing group rating is acceptable. However, if you are transporting DOT- regulated hazardous materials, the packing group rating on the IBC must match or exceed the packing group assigned to the substance. Shipping a Packing Group II chemical in a Z-rated IBC is a federal violation.
Compliance Implications for Your Business
UN ratings are not optional for businesses that ship or receive hazardous materials. The DOT requires that all packaging used for hazmat transport bear valid UN markings that correspond to the hazard class and packing group of the contents. Violations can result in fines of up to $75,000 per occurrence and criminal penalties for willful non-compliance.
Even for non-hazmat applications, UN ratings serve as a quality indicator. A UN-rated IBC has been drop-tested, stacking-tested, pressure-tested, and leak-tested by an accredited laboratory. Buying an unrated or counterfeit IBC exposes you to product loss, environmental contamination, and liability.
When purchasing used IBC totes or reconditioned IBCs, always verify that the UN marking is legible and intact. If the marking has been painted over, scraped off, or is otherwise unreadable, the IBC cannot legally be used for hazmat transport. Our compliance resource page has more details on federal and state regulations for IBC usage.
Reconditioned IBCs that receive a new inner bottle must be re-tested and re-marked with a new UN rating by the reconditioner. Check for a reconditioner's mark (usually "R" followed by the reconditioner's registration number and the reconditioning date) in addition to the original manufacturer's UN marking.
UN Rating Expiration and Retest Intervals
Composite IBCs (UN 31HA1 and similar) have a maximum service life of five years from the date of manufacture for hazardous materials transport. After five years, the IBC must be taken out of hazmat service unless it is inspected and re-certified. This five-year clock is based on the manufacture date stamped in the UN marking, not the date of purchase.
Additionally, composite IBCs must pass a 2.5-year inspection (30 months from manufacture). This inspection verifies the structural integrity of the cage, the condition of the HDPE bottle, the function of valves and closures, and the legibility of markings. Failure to perform this inspection renders the IBC non-compliant for hazmat use.
For non-hazmat applications, there is no federal expiration date. Used IBCs past their five-year hazmat window remain perfectly functional for water storage, agricultural use, and DIY projects. This is why used IBC totes are so affordable -- they have aged out of hazmat certification but still have years of useful life ahead of them.
Practical Tips for Buyers
When shopping for IBCs, always ask the seller for the full UN marking. Reputable dealers like Omaha IBC Tanks document and verify UN codes on every tank we sell. If you need an IBC for hazmat transport, confirm the manufacture date is within the five-year window and that the packing group rating matches your substance requirements.
Visit our specifications page for detailed technical data on the IBCs we stock, or contact us with questions about specific UN ratings. We are always happy to help you find a compliant container for your application.