Every approved dangerous goods drum, jerrican, box and IBC carries a short string of codes that shows what it was built and tested to hold. Packaging manufacturers often explain it in terms of the UN Model Regulations (the “Orange Book”). For road transport in Great Britain, the same marks are set out in ADR 6.1.3 for packagings and ADR 6.5.2 for IBCs. The mark is the same, but the legal source is ADR.
The packer and the consignor are responsible for choosing the right packaging (ADR 1.4.2.1 and 1.4.3.2). Even so, a driver who can read the mark will notice sooner when something on the load doesn’t fit.
The type code: what the packaging is
After the circled “UN” symbol, the first group of characters identifies the packaging. It is built from three parts:
| Position | Meaning | Common values |
|---|---|---|
| Number | Kind of packaging | 1 = drum, 3 = jerrican, 4 = box, 5 = bag, 6 = composite |
| Letter | Material | A = steel, B = aluminium, G = fibreboard, H = plastics, N = other metal |
| Final number | Category within the type | For drums and jerricans: 1 = non-removable head, 2 = removable head |
Some common examples:
| Code | What it is |
|---|---|
| 1A1 | Steel drum, non-removable (tight) head |
| 1A2 | Steel drum, removable (open) head |
| 1H1 | Plastics drum, non-removable head |
| 3H1 | Plastics jerrican, non-removable head |
| 31HA1 | Composite IBC for liquids, rigid plastics inner receptacle |
Tight-head drums are normally used for liquids. Open-head drums are mostly used for solids and pastes, although some are approved for liquids.
The performance letter: X, Y or Z
Next comes a single letter. It refers to packing groups, not to hazard classes. This is a common mistake, and even some manufacturer explainers mix the two up. The packing group shows how dangerous a substance is within its class. The letter shows the most dangerous packing group the packaging passed its tests for.
| Letter | Tested to | May carry goods of |
|---|---|---|
| X | Packing group I (high danger) | PG I, II and III |
| Y | Packing group II (medium danger) | PG II and III |
| Z | Packing group III (low danger) | PG III only |
A Y-marked drum is fine for a PG III substance. A Z-marked drum must never be used for PG II goods. The packing group appears in the transport document entry required by ADR 5.4.1, so you can compare the two. The UN packaging mark and packing groups post covers this check in more detail. If you need the class background, see dangerous goods classes explained.
The rest of the string
After the letter, the mark gives figures that differ for liquids and solids:
| Element | Packaging for liquids | Packaging for solids or inner packagings |
|---|---|---|
| Number after X/Y/Z | Relative density the design was tested to (may be omitted if 1.2 or less) | Maximum gross mass in kg |
| Next field | Hydraulic test pressure in kPa | The letter “S” |
| Year | Last two digits of the year of manufacture | Same |
| Country | Distinguishing sign of the authorising state (GB for the UK) | Same |
| Manufacturer | Name or code of the maker or approval holder | Same |
Two worked examples:
| Mark | Reading |
|---|---|
| UN 1A2/Y225/S/26/GB/… | Open-head steel drum, PG II and III, maximum 225 kg gross, for solids, made in 2026, approved in Great Britain |
| UN 1A1/X1.4/250/26/GB/… | Tight-head steel drum, PG I–III, liquids up to relative density 1.4, tested at 250 kPa, made in 2026 |
Some packagings carry extra marks:
| Packaging | Additional marking |
|---|---|
| Plastics drums and jerricans | Month of manufacture, often shown as a clock dial |
| Reconditioned drums | “R”, the reconditioner and the date of reconditioning (ADR 6.1.3) |
| Recycled plastics | “REC” |
| IBCs (ADR 6.5.2) | Stacking load, tare mass, and the date of the last leakproofness test and inspection |
For plastics packagings and IBCs, the chemical compatibility testing the manufacturer mentions takes place before approval. The mark shows that the design passed the test. It does not show that the packaging suits every substance. Compatibility is still the packer’s decision.
What this means at the loading bay
You are not certifying the packaging. You are, however, the last person to see the load before it goes on the road. Treat these as stop-and-ask signs:
- a packing group in the paperwork that the X/Y/Z letter doesn’t cover;
- a solids mark (“S”) on a drum that is obviously holding liquid;
- a gross mass in the mark that the package plainly exceeds;
- missing, painted-over or illegible UN marks; and
- damage, corrosion or leakage. Do not accept a damaged or leaking package.
If any of these turn up, don’t load it. Refer it to the consignor, the loader or your DGSA. Taping over a split or swapping a label is never an acceptable fix. Package counts also affect your load thresholds under ADR 1.1.3.6, which is covered in ADR 1.1.3.6 load points.
How ADR Driver Pro Fits Into This
Packaging marks, packing groups and package-level checks are part of the core packages content in ADR Driver Pro. They come up across the 13 modules, which cover the core syllabus and the individual hazard classes. The packages route is one of the app’s 6 driver routes and focuses on the knowledge you need when you’re carrying drums, jerricans and IBCs rather than tanks.
To practise, the app has 1820 revision questions, of which 110 are free, including questions on reading UN marks and matching X, Y and Z to packing groups. The 8 quick reference sets give you the marking tables offline. The 5 calculators include the 1.1.3.6 load-points calculation, and the 6 field tools are there for when you’re standing at the back of the trailer with the documents.
