Quick answer: A UN Approval Marking is an internationally recognised code displayed on dangerous goods packaging that confirms the packaging has been independently tested and certified to United Nations performance standards.
The UN marking is made up of a sequence of letters and numbers printed on packaging that has been tested for the transport of dangerous goods. It tells you the packaging type and material, the packing group it was tested to, its mass or density limit, whether it is approved for solids or liquids, the year and country of manufacture, and the approval holder’s certificate number.
If you ship dangerous goods by road, sea or air, you need to be able to look at a the packaging and tell within whether it is right for the job. This guide walks through every element of the mark, gives you the full code tables, and covers the traps that catch people out.
You can download our printable PDF one page UN approval quick reference guide or further information can be found below in our detailed guide.
What is a UN approval marking?
UN Approval Markings are internationally recognised identification codes applied to packaging that has been tested and certified for the transport of dangerous goods.
Rather than identifying the chemical or hazardous material inside the package, the marking confirms that the packaging itself has successfully passed a series of demanding performance tests.
These tests are designed to simulate the conditions packaging may experience during transport, including:
- Drop testing
- Leak testing
- Hydrostatic pressure testing
- Stacking tests
- Vibration and handling stresses
Only packaging that successfully passes the required tests may display an official UN approval marking.
A typical UN approval marking can provide information including:
- Packaging type
- Construction material
- Open head or tight head design
- Packing Groups the packaging has been certified for
- Maximum specific gravity (liquid packaging)
- Maximum gross mass (solid packaging)
- Hydrostatic pressure rating
- Year of manufacture
- Country of certification
- Manufacturer identification
As these markings are internationally standardised, a UN approved drum manufactured in one country can generally be recognised and understood anywhere in the world.
For businesses transporting chemicals, paints, oils, adhesives, food ingredients, pharmaceuticals and many other regulated products, understanding these markings is essential for selecting compliant packaging.
Packaging carrying the mark is commonly described as UN approved or performance tested packaging. Both usually the same thing.
Which regulations require it?
The markings are based on the United Nations Recommendations on the Transport of Dangerous Goods (Model Regulations) and are recognised worldwide through transport regulations including:
- ADR (Road Transport)
- IMDG Code (Sea Freight)
- RID (Rail Transport)
- ICAO Technical Instructions
IATA Dangerous Goods Regulations (Air Transport)
The anatomy of a UN marking
Every UN mark is built from the same eight elements in the same order. Two of those elements change meaning depending on whether the packaging was tested for solids or for liquids, which is the single biggest source of confusion.
The mark may be applied on one line or split across several, and the forward slashes are a convention rather than a strict requirement, but the sequence never changes. If you read left to right, top to bottom, you will always hit the elements in this order.
Once you understand the structure, reading a UN marking becomes straightforward. Each section follows a logical order, allowing you to quickly determine:
- What type of packaging it is.
- Whether it is suitable for liquids or solids.
- Which hazard level it has been approved for.
- The maximum performance it has been tested to.
- Where it was certified.
- Who manufactured it.
In the following sections, we’ll examine every part of the marking in more detail, explaining exactly what each letter and number means and how it affects the packaging’s intended use.
Understanding Every Part of the Code
Now that you’ve seen the overall structure of a UN approval marking, let’s look at what each section means in more detail.
1. The UN symbol
The circled un symbol, or the letters UN where the symbol cannot be reproduced. On embossed metal packaging you will often see the plain capital letters instead. Its presence signals that everything following it is a UN specification, not a manufacturer’s part number.
2. Packaging identification code
Immediately after the UN symbol is the packaging type code. This first number simply tells you the general style of packaging. The letter following the packaging type identifies the material used to manufacture the outer packaging
Type digit
| Code | Packaging type |
| 1 | Drum |
| 2 | Barrels |
| 3 | Jerrican |
| 4 | Box |
| 5 | Bag |
| 6 | Composite packaging |
Material letter
| Code | Material |
| A | Steel |
| B | Aluminium |
| C | Natural wood |
| D | Plywood |
| F | Reconstituted wood |
| G | Fibreboard |
| H | Plastics |
| L | Textile |
| M | Paper, multiwall |
| N | Metal other than steel or aluminium |
| P | Glass, porcelain or stoneware |
Category digit
Where a type and material combination comes in more than one form, a third character distinguishes them. For drums and jerry cans it identifies the “head”:
Head type
| Code | Packaging type |
| 1 | Tight Head (Closed Head) |
| 2 | Open Head (removable Lid) |
Examples:
1A1 = Steel Tight Head Drum
1H2 = Plastic Open Head Drum
A tight head drum has permanently fixed ends and is generally used for liquids.
An open head drum has a removable lid secured with a locking ring, making it suitable for solids, powders, pastes and products that require easier filling or emptying.
Some codes carry no category digit at all, for example, a fibreboard box is simply 4G.
Qualifying letters
A letter appended after the identification code signals a special packaging type:
| Letter | Meaning |
| V | Special packaging tested with a defined range of inner packagings, giving flexibility over what may be packed inside (e.g. 4GV) |
| U | Special packaging for infectious substances |
| W | Same packaging type, manufactured to a different specification but assessed as equivalent |
| T | Salvage packaging, for recovering damaged or leaking packages |
The distinction between 4G and 4GV matters more than almost anything else in the mark. A plain 4G is approved only with the specific inner packaging named in its test report. A 4GV has been tested to a tougher standard and permits a broader range of inners within stated limits.
3. Packing group tested to
After the packaging code you’ll normally see one of three letters; X, Y or Z. This is one of the most important parts of the entire marking because it identifies which Packing Groups the packaging has successfully passed testing for.
| Letter | Packing group | Also permitted for |
| X | I — high danger | II and III |
| Y | II — medium danger | III |
| Z | III — low danger |
As X-rated packaging has passed the most demanding performance tests, it can also be used where Y or Z packaging is required, provided all other limitations are satisfied. However, the reverse is not true. For example, a Y-rated drum cannot normally be used for a Packing Group I product.
4. Gross mass or relative density
Here the mark forks depending on what the packaging was tested with.
Solids: a whole number giving the maximum gross mass in kilograms ie the packaging plus everything in it. Y15 means 15 kg gross, not 15 kg of product.
Liquids: a decimal figure giving the relative density (specific gravity) the design was tested to. Where the relative density does not exceed 1.2 it may be omitted from the mark entirely, and a mark with no density figure should be read as 1.2.
Reading a solids figure as a volume is one of the most common misreadings in the whole mark. It is mass, and it is gross.
5. Solids designation or hydraulic test pressure
Solids: the letter S.
Liquids: a number giving the hydraulic test pressure in kilopascals, rounded down to the nearest 10 kPa.
If you see an “S”, the packaging is not approved for liquids as a single packaging. It may still legitimately carry liquids in a combination packaging, where the liquid sits in tested inner packaging and the marked outer is approved for those inners but that permission comes from the test report, not from the mark.
Where a design has been tested for both solids and liquids it carries two separate marks, one for each.
6. Year of manufacture
Most UN markings include the year in which the packaging was manufactured. For example 26 indicates the packaging was manufactured during 2026.
The manufacturing year provides traceability and helps identify the production batch if required.
7. Country of Approval
The following letters identify the country that authorised the UN approval.
Examples include:
Code Country
GB United Kingdom
NL Netherlands
DE Germany
FR France
IT Italy
US United States
This identifies the competent authority responsible for the approval rather than the country where the packaging is necessarily being used.
8. Approval holder’s code
A code allocated to the certificate holder, sometimes combined with a manufacturer’s symbol. Every manufacturer has its own unique approval code. This provides full traceability should regulators or customers need to verify the packaging’s origin.
Worked example: a 1A1 steel drum
UN 1A1/X1.4/250/26/GB/1234
1A1 – A steel drum with a non-removable head
X – Tested to Packing Group I, so usable for PG I, II and III goods
1.4 – Tested with a liquid of relative density up to 1.4
250 – Hydraulic test pressure of 250 kPa
26 – Manufactured in 2026
GB – Authorised in Great Britain
1234 – Approval holder’s code
The absence of an S and the presence of a density and pressure figure tell you immediately that this is a liquids approval. The same drum with a removable head would be marked 1A2.
Quick reference tables
Packaging types
| Code | Type |
| 1 | Drum |
| 2 | Reserved |
| 3 | Jerrican |
| 4 | Box |
| 5 | Bag |
| 6 | Composite |
Materials
| Code | Material |
| A | Steel |
| B | Aluminium |
| C | Natural wood |
| D | Plywood |
| F | Reconstituted wood |
| G | Fibreboard |
| H | Plastics |
| L | Textile |
| M | Paper, multiwall |
| N | Other metal |
| P | Glass, porcelain, stoneware |
Packing groups
| Letter | Group | Danger | Covers |
| X | I | High | I, II, III |
| Y | II | Medium | II, III |
| Z | III | Low | III |
Common codes you will see in the field
| Code | Packaging |
| 4G | Fibreboard box |
| 4GV | Fibreboard box, variable inners |
| 4D | Plywood box |
| 4H2 | Solid plastics box |
| 1A1 | Steel drum, closed head |
| 1A2 | Steel drum, open head |
| 1H1 | Plastic drum, closed head |
| 1G | Fibreboard drum |
| 3H1 | Plastic jerrican, closed head |
| 5H4 | Plastics film bag |
Frequently asked questions
What does UN approved packaging mean?
It means the packaging design has been performance tested and certified against the UN Model Regulations for the transport of dangerous goods. Testing typically covers drop, stack and leak proofness, with a hydraulic pressure test for liquid packaging.
What is the difference between X, Y and Z on UN packaging?
They show the packing group the design was tested to. X was tested to Packing Group I and may be used for Packing Group I, II or III. Y was tested to Packing Group II and may be used for Packing Group II or III. Z was tested to Packing Group III only.
What does the S mean in a UN marking?
S means the packaging is approved for solids or for use with inner packaging. Where there is no S, the two figures in its place give the relative density and the hydraulic test pressure, indicating a liquids approval.
Does UN approved packaging expire?
The UN approval itself does not have an expiry date. However, some packaging types, particularly plastic drums and jerry cans used for transporting certain dangerous goods, may be subject to maximum service life requirements under transport regulations. Packaging should always be inspected before reuse and must remain in good condition.
Where should the UN marking appear on the package?
It must be durable, legible and readily visible, positioned and sized in proportion to the packaging. On drums it is usually embossed or printed on the body or head; on boxes it is normally printed on a side panel.
Can I use packaging rated for a higher packing group?
Yes. Approval runs downward, so X-rated packaging may be used for PG II and PG III goods and Y-rated for PG III. The reverse is never permitted.
What does 1A1 mean on a drum?
1 is a drum, A is steel, and the final 1 indicates a non-removable (closed) head. A 1A2 is the same drum with a removable head.
What is specific gravity?
Specific gravity measures the density of a liquid compared with water. Water has a specific gravity of 1.0. If a drum is marked Y1.9, it has been tested for liquids with a maximum specific gravity of 1.9. Using a container for liquids heavier than its certified specific gravity may not comply with dangerous goods regulations.
What is hydrostatic pressure?
Hydrostatic pressure is the pressure exerted by a liquid inside a container. During UN performance testing, liquid packaging is subjected to internal pressure to ensure it can safely withstand transport conditions without leaking or bursting. The hydrostatic pressure rating shown on the approval marking confirms the pressure the packaging successfully passed during testing.
Is every hazardous product required to be transported in UN approved packaging?
Whether UN approved packaging is required depends on the classification of the substance, the quantity being transported, any applicable exemptions and the transport regulations being followed. Always refer to the relevant dangerous goods regulations or seek professional advice if you’re unsure.
Can I transport food products in UN approved drums?
Yes, provided the drum is manufactured from a food contact compliant material where required and is suitable for the intended contents. A UN approval marking confirms the packaging has passed dangerous goods performance testing, but it does not automatically indicate food grade compliance. Always verify both the UN certification and any applicable food-contact approvals.
Need help selecting compliant packaging?
Reading the mark is the first step; matching it to your substance, packing instruction and mode of transport is the part that takes experience. Get in touch with the team at ITP Packaging and we will help you confirm whether a packaging specification is right for what you are shipping.
This guide is provided for general information and was correct to the best of our understanding at the time of publication. Always refer to the current edition of the applicable modal regulation and the test report for your specific packaging.