If you have ever looked closely at an IBC tank, you have probably noticed a series of cryptic numbers, letters, and symbols stamped or embossed on the bottle or printed on a metal data plate attached to the cage. These are the UN (United Nations) certification markings, and they contain a wealth of critical information about the container's design, materials, test ratings, manufacturer, and compliance status. Understanding these markings is essential for anyone involved in purchasing, shipping, or storing materials in IBC tanks — particularly hazardous materials. In this guide, we break down every element of the UN marking system and explain what each code means in practical terms.
Why UN Markings Matter
UN markings are not just regulatory fine print. They serve several critical functions in the supply chain. First, they verify that the IBC design has been tested and certified to meet international performance standards established by the United Nations Committee of Experts on the Transport of Dangerous Goods. Second, they encode the IBC's specifications — type, material, maximum weight, and test ratings — allowing shippers and regulators to verify that a specific container is authorized for a specific material. Third, they provide traceability, linking the container back to its manufacturer and date of production.
For hazardous materials transportation, using an IBC without valid UN markings (or with expired markings) is a violation of DOT regulations under 49 CFR Part 178, Subpart N. Fines for shipping hazmat in a non-certified or expired IBC can exceed $50,000 per violation. For more on transportation regulations, see our guide on transporting IBC totes safely.
Anatomy of a UN Marking: Line by Line
A typical UN marking on a composite IBC (HDPE bottle in a steel cage) looks something like this:
UN 31H1/Y/1900/0822
USA/M5678
SG 1.9 / TP 2650 / 275 GAL
Schütz / Milwaukee WI
Let us decode each element of this marking system.
Element 1: The UN Symbol and IBC Type Code
The marking always begins with “UN” (often displayed as the stylized UN emblem — a lowercase “u” over a lowercase “n” inside a circle). This symbol confirms that the IBC has been certified under the UN system. Immediately following the UN symbol is the IBC type code, which is a combination of numbers and letters that identifies the container type and material.
| Code | IBC Type | Description |
|---|---|---|
| 11A | Metal, steel | Rigid metal IBC for liquids, made entirely of steel |
| 21H1 | Rigid plastic | HDPE rigid plastic IBC with structural equipment (no cage) |
| 31H1 | Composite, rigid plastic inner | HDPE bottle inside a rigid outer cage (most common IBC type) |
| 31HA1 | Composite, rigid plastic inner, steel cage | HDPE bottle specifically in a steel cage structure |
| 13H1 | Flexible | Flexible IBC (woven fabric) with plastic liner |
The first digit indicates the IBC category: 1 = rigid, 2 = rigid with structural equipment, 3 = composite. The second digit indicates whether the IBC is for 1 = solids (with a gravity discharge), 1 = solids (pressure discharge), or 1 = liquids. The letter indicates the material: A = steel, B = aluminum, H = plastic, N = wood. The final digit (1 or 2) specifies the sub-type within that category.
Element 2: Packing Group Rating
Immediately after the type code, a single letter indicates the packing group rating:
- •X: Approved for Packing Groups I, II, and III (most stringent — suitable for high-danger materials)
- •Y: Approved for Packing Groups II and III (medium danger)
- •Z: Approved for Packing Group III only (minor danger)
Most composite IBCs (31H1) carry a Y or Z rating. An X-rated IBC has passed more demanding drop and pressure tests and is required for transporting Packing Group I materials, which include the most dangerous substances in each hazard class. If you need to ship a Packing Group I material, you must use an X-rated IBC — a Y or Z container is not legally permitted regardless of how sturdy it appears.
Element 3: Maximum Gross Mass
The marking includes the maximum gross mass in kilograms (or sometimes pounds). This figure represents the total weight the IBC is rated to carry, including the weight of the contents plus the weight of the container itself. For a standard 275-gallon composite IBC, the maximum gross mass is typically 1,500 kg (3,307 lbs). Never exceed this weight limit, as doing so voids the UN certification and creates a significant safety and liability risk. For dense chemicals, the maximum gross mass may be the limiting factor rather than the volume capacity — see our article on chemical compatibility for specific gravity considerations.
Element 4: Date of Manufacture
The date code indicates when the IBC was manufactured, typically expressed as a two-digit month and two-digit year (e.g., 08/22 for August 2022) or as a four-digit year-month (0822). This date is critically important because UN certification has a limited validity period. For composite IBCs used to transport hazardous materials, the maximum service life from date of manufacture is typically 5 years. After 5 years, the IBC must be requalified (retested and reinspected by an approved facility) or retired from hazmat service. Non-hazmat applications have no regulatory expiration, but the date code still helps assess the age and expected remaining service life of the container.
Element 5: Country and Approval Number
The marking includes the country code (e.g., USA, D for Germany, NL for Netherlands) and the approval or registration number assigned by the national competent authority. In the United States, this number is assigned by DOT through registered third-party testing laboratories. The country code and approval number allow regulators to trace the IBC certification back to the specific design test report and the laboratory that conducted the testing.
Element 6: Specific Gravity and Test Pressure
Two additional performance parameters are encoded in the marking:
- •Specific Gravity (SG): The maximum specific gravity of the contents for which the IBC is rated. For example, SG 1.9 means the IBC is approved for liquids with a density up to 1.9 g/cm³. Water has an SG of 1.0; sulfuric acid (concentrated) has an SG of 1.84. If your chemical has an SG exceeding the IBC's rating, you cannot legally use that container for transport.
- •Hydraulic Test Pressure (TP): The pressure in kPa (kilopascals) at which the IBC was hydraulically tested. The test pressure must equal or exceed the vapor pressure of the contents at 55°C plus the hydrostatic head of the contents. A typical test pressure for a composite IBC is 75-100 kPa (approximately 11-15 psi).
Element 7: Manufacturer and Location
The final line of the UN marking typically identifies the IBC manufacturer and their location. Major IBC manufacturers whose markings you will frequently encounter include Schütz, Mauser Packaging Solutions (now part of MAUSER Group), Greif, and Time Technoplast. The manufacturer name is important for sourcing replacement parts (valves, gaskets, caps) and for verifying the authenticity of the container. Counterfeit or unauthorized IBCs bearing fraudulent UN markings do exist in the market — purchasing from reputable suppliers like IBC Recycle Services ensures authenticity.
Reconditioned IBC Markings
When an IBC is reconditioned (fitted with a new bottle inside the existing cage), additional markings are applied. The reconditioned IBC receives a new UN marking from the reconditioner that includes:
- The reconditioner's UN marking:A complete new UN marking reflecting the reconditioned IBC's type, packing group, gross mass, and test date. This marking supersedes the original manufacturer's marking for regulatory purposes.
- The reconditioning date: The date the reconditioning was performed, which resets the 5-year service life clock for hazmat use.
- The reconditioner's identification: Name and location of the facility that performed the reconditioning.
- The letter “R” or “L”:“R” indicates a rebuilt IBC (new bottle, may include cage repair), while “L” indicates a routine maintenance reconditioning.
The original manufacturer's marking should still be visible on the cage, but it is the reconditioner's marking that determines the IBC's current certification status. For more information on industry standards, visit our industry standards page.
How to Read the Marking on Your IBC
Here is a step-by-step process for reading and interpreting the UN marking on any IBC you encounter:
- Locate the marking. On composite IBCs, look for a molded or embossed marking on the HDPE bottle (usually near the top) and/or a metal data plate riveted to the steel cage.
- Confirm the UN symbol.The presence of “UN” or the UN emblem confirms this is a certified container. If there is no UN marking, the IBC is not certified for hazmat transport.
- Read the type code. Identify the type (e.g., 31H1 = composite with HDPE inner, rigid outer) to confirm it matches your application requirements.
- Check the packing group. Verify that the rating (X, Y, or Z) is sufficient for the packing group of the material you intend to ship.
- Verify the date. Calculate whether the IBC is within its 5-year service life for hazmat use. For non-hazmat applications, note the age as a general condition indicator.
- Check specific gravity. Ensure the SG rating meets or exceeds the specific gravity of your intended contents.
Key Takeaways
- The UN marking confirms the IBC has been tested and certified to international standards
- 31H1 is the most common type code for composite HDPE/steel IBCs
- Packing group ratings (X, Y, Z) determine which hazard levels the IBC can carry
- Composite IBCs have a 5-year hazmat service life from date of manufacture
- Reconditioned IBCs receive new UN markings that reset the certification clock
Complete UN IBC Type Code Reference
While the most common codes were covered above, the UN system includes a comprehensive set of type codes for every IBC configuration. This expanded reference table covers all major types you may encounter.
| Code | Category | Material | Description | Use |
|---|---|---|---|---|
| 11A | Rigid Metal | Steel | All-steel rigid IBC for liquids | Solvents, fuels, aggressive chemicals |
| 11B | Rigid Metal | Aluminum | All-aluminum rigid IBC for liquids | Lightweight, corrosion-resistant applications |
| 11N | Rigid Metal | Other metal | Rigid IBC of other metal (e.g., alloys) | Specialty chemical applications |
| 21H1 | Rigid Plastic | HDPE | Rigid plastic IBC with structural equipment | Standalone plastic tanks without cage |
| 21H2 | Rigid Plastic | HDPE | Rigid plastic IBC, freestanding | Self-supporting plastic vessels |
| 31H1 | Composite | HDPE + Rigid Outer | HDPE bottle in rigid outer packaging | Most common IBC type worldwide |
| 31HA1 | Composite | HDPE + Steel Cage | HDPE bottle specifically in steel cage | Standard cage-frame composite IBC |
| 31HB1 | Composite | HDPE + Aluminum Cage | HDPE bottle in aluminum cage | Lighter weight, corrosion-resistant cage |
| 13H1 | Flexible | Woven Plastic | Flexible IBC with plastic liner | Dry bulk solids (powders, granules) |
Real-World Scenario: How a Misread Marking Led to a $55,000 Fine
Case Study: Regional Chemical Shipper
A regional chemical shipping company in Ohio received a DOT inspection during a routine traffic stop. The inspector examined eight IBCs on the flatbed trailer, all containing Packing Group II corrosive liquids (sulfuric acid at 40% concentration). The IBC UN markings showed “31H1/Z” — Packing Group III only. The “Z” rating was insufficient for Packing Group II materials.
The root cause: the warehouse team had been trained to check for the UN symbol but not to verify the packing group letter. They assumed all UN-certified IBCs were interchangeable for all hazmat classifications. The DOT inspector issued citations for all eight IBCs, resulting in fines totaling $55,200 ($6,900 per container). The shipment was placed out of service until Y-rated or X-rated IBCs could be sourced and the product transferred.
The company subsequently implemented a three-step verification checklist that every loader must complete before sealing a hazmat IBC shipment:
- Confirm the UN symbol is present and legible on every IBC
- Verify the packing group rating (X, Y, or Z) matches or exceeds the material's packing group
- Check the manufacture date to confirm the bottle is within the 5-year service life
Since implementing this checklist, the company has had zero DOT marking violations in three years of inspections.
Pro Tips: Working with UN Markings
Purchasing Tips
- 1.Always request a photo of the UN marking plate before purchasing used or reconditioned IBCs remotely. A legible marking is essential for compliance — if it is faded, corroded, or missing, the IBC cannot legally be used for hazmat transport.
- 2.When buying reconditioned IBCs, verify that the reconditioner's marking is present in addition to (not replacing) the original manufacturer's cage marking. Both should be visible and legible.
- 3.If you ship Packing Group I materials, specify X-rated IBCs in your purchase order explicitly. Do not assume that a “UN-certified” IBC meets your needs without checking the rating letter.
Compliance Tips
- 1.Maintain a digital database of all IBCs in your fleet with their UN marking data, including type code, packing group, manufacture date, and SG rating. This allows instant compliance verification and simplifies DOT inspection responses.
- 2.Set up automatic alerts for IBCs approaching their 2.5-year inspection interval and 5-year bottle expiration. Proactive scheduling prevents compliance gaps and avoids the scramble of emergency replacements.
- 3.Train forklift operators and warehouse staff to report damaged or illegible marking plates immediately. A DOT inspector can cite any IBC with an unreadable marking, regardless of the container's actual condition or age.
Common Mistakes to Avoid with UN Markings
- 1.Using a reconditioned IBC with only the original manufacturer's markings.
When an IBC is reconditioned, the reconditioner must apply their own UN marking that reflects the new bottle's test results and date. Using a reconditioned IBC that lacks the reconditioner's marking is a regulatory violation, even if the original marking is still visible. The original marking applies to the original bottle, which has been replaced.
- 2.Confusing the bottle date with the cage date.
Composite IBCs have two date codes: one for the bottle (on the HDPE itself) and one for the cage (on the metal data plate). The 5-year service life limit applies to the bottle date, not the cage date. An IBC with a 2019 cage date and a 2024 bottle date (rebottled) is fully compliant for hazmat use through 2029.
- 3.Painting over or obscuring UN markings during container refurbishment.
When cleaning, painting, or labeling IBCs, ensure that the UN marking plate remains fully visible and legible. Painting over the data plate, covering it with adhesive labels, or allowing rust to obscure it renders the IBC non-compliant for hazmat transport.
- 4.Ignoring the SG (specific gravity) rating for dense chemicals.
A 275-gallon IBC rated for SG 1.5 can only hold approximately 220 gallons of a chemical with SG 1.9 without exceeding the maximum gross mass. Filling to full volume with a dense chemical overloads the container structurally and voids the UN certification. Always calculate the maximum fill volume based on both the volumetric capacity and the gross mass limit.
- 5.Applying the 5-year rule to non-hazmat applications.
The 5-year bottle service life is a DOT hazmat transport requirement. IBCs used for non-regulated products (water, food, non-hazardous chemicals) have no regulatory age limit. A 7-year-old HDPE bottle that passes visual inspection and is structurally sound can continue in non-hazmat service indefinitely. Replacing containers prematurely based on a misunderstanding of this rule wastes money.
Myths vs Facts: UN IBC Markings
Myth: Any IBC with a UN marking can carry any hazardous material.
Fact:The UN marking specifies exactly which hazard levels (packing groups), maximum densities (SG), and test pressures the IBC is approved for. A Z-rated IBC can only carry Packing Group III materials. An IBC rated for SG 1.5 cannot carry liquids denser than 1.5 g/cm³. The marking must match or exceed the requirements of the specific material being shipped.
Myth: UN markings are only important for international shipping.
Fact: The United States has adopted the UN marking system through 49 CFR and requires it for all domestic hazardous material transport in IBCs. Whether you are shipping across state lines or across town, the UN marking requirements are identical. Even intrastate movements of hazmat in IBCs require valid UN certification.
Myth: Once the 5-year service life expires, the IBC must be scrapped.
Fact: An IBC that exceeds its 5-year bottle limit can be reconditioned (rebottled), which resets the clock. Alternatively, it can be repurposed for non-hazmat applications where the 5-year rule does not apply. The cage, which typically has a 15-25 year structural life, should not be scrapped just because the bottle has expired for hazmat service. Reconditioning maximizes the value of the long-lived cage.
Myth: The 2.5-year periodic inspection must be performed by the original manufacturer.
Fact: Periodic inspections can be performed by any qualified person or facility, including the container owner, as long as the inspection follows the requirements of 49 CFR 180.352. The inspector does not need to be the manufacturer or an authorized distributor. However, the inspection must be documented with date, inspector identification, findings, and pass/fail determination.
Frequently Asked Questions
Where exactly is the UN marking located on a composite IBC?+
Composite IBCs typically have two marking locations. The HDPE bottle has the UN marking molded or embossed directly into the plastic, usually near the top of the bottle on the front face. The steel cage has a metal data plate riveted to one of the cage uprights, usually on the front near the top. The bottle marking contains the bottle-specific data (material, date, manufacturer), while the cage plate may contain cage-specific information. For reconditioned IBCs, the reconditioner's marking is typically a separate metal plate or adhesive label attached to the cage.
Can I get a replacement UN marking plate if mine is damaged?+
You cannot simply fabricate a replacement marking plate — that would constitute counterfeiting a UN certification. If the cage data plate is damaged but the bottle marking is legible, the IBC may still be identifiable. If both markings are lost, the IBC must be returned to a certified reconditioner who can test and remark the container, or it must be retired from hazmat service. For non-hazmat use, a container with missing markings can continue in service.
What does the “R” vs “L” designation mean on a reconditioned IBC marking?+
The letter “R” indicates a rebuilt IBC, meaning the bottle has been replaced and the cage may have undergone structural repairs. This is the most common reconditioning type. The letter “L” indicates routine maintenance, which includes activities like cleaning, replacing gaskets and valves, and minor repairs that do not involve bottle replacement. An “L” marking does not reset the 5-year service life clock because the original bottle is still in use. An “R” marking does reset the clock because a new bottle has been installed.
Do IBCs used for non-hazardous materials need UN markings?+
No. UN markings are required only for IBCs used to transport hazardous materials as defined under DOT regulations (49 CFR). IBCs used exclusively for non-hazardous products (water, food ingredients, non-regulated chemicals) do not need UN certification. However, even non-hazmat IBCs must meet general transportation requirements for safe loading, securement, and handling. Many buyers prefer UN-marked IBCs even for non-hazmat use because the certification provides assurance of design quality and structural testing.
How do I calculate the maximum fill volume for a dense chemical?+
The maximum fill volume is determined by the lesser of two limits: the volumetric capacity (e.g., 275 gallons) and the gross mass capacity divided by the product density minus the tare weight. For example, if an IBC has a gross mass rating of 1,500 kg (3,307 lbs) and a tare weight of 130 lbs, the maximum product weight is 3,177 lbs. For a chemical with SG 1.8 (15.0 lbs/gallon), the maximum fill volume would be 3,177 / 15.0 = 212 gallons — significantly less than the 275-gallon volumetric capacity. Always perform this calculation for chemicals with SG above 1.3.
Need UN-Certified IBC Tanks?
All IBC tanks from IBC Recycle Services come with verified UN markings and full documentation. Browse our inventory or contact us for specific certification requirements.