This session comes from a general dangerous-goods class in Malaysia rather than a UK ADR course, and the instructor reads from a combined “DG book” that mixes regimes. The good news is that the UN packaging mark itself comes from the UN Model Regulations, so the string stamped on a fibreboard box or plastic drum reads the same under ADR, IMDG and IATA. What differs is the law that binds the driver. For a driver in Great Britain that is ADR 2025, applied through the Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations, and the mark is specified at ADR 6.1.3.
Packing groups and the letters X, Y and Z
ADR 2.1.1.3 assigns most substances in Classes 3, 4.1, 4.2, 4.3, 5.1, 6.1, 8 and 9 to one of three packing groups according to their degree of danger. The packaging mark does not print “I”, “II” or “III”. It uses a performance letter, which tells you the most severe group the packaging has been tested for.
| Packing group | Degree of danger | Mark letter | Packagings that may be used |
|---|---|---|---|
| I | High | X | X only |
| II | Medium | Y | X or Y |
| III | Low | Z | X, Y or Z |
An X-marked packaging can therefore carry Packing Group II or III goods, subject to the mass or density figure that follows the letter. A Z-marked packaging can never carry Packing Group I or II goods. The transcript gets this right, and it is the single most useful thing to remember on a loading bay.
Combination and single packagings
The instructor demonstrates the two designs a package driver meets most often. ADR 4.1 packing instructions decide which design a substance may travel in, and the marking differs slightly between them.
| Design | What it is | Typical mark | What the number after the letter means |
|---|---|---|---|
| Combination packaging | Inner packagings (bottles, tins, bags) inside an outer packaging | UN 4G/X5/S/18/GB/AB123 | Maximum gross mass of the whole package in kg |
| Single packaging for liquids | One packaging holding the liquid directly | UN 1H1/Y1.4/150/17/F/VL823 | Maximum relative density of the liquid it was tested for |
| Single packaging for solids | One packaging holding the solid directly | UN 1A2/X50/S/18/GB/AB123 | Maximum gross mass in kg |
The transcript describes a 4G fibreboard box marked X5 as “5 kilogram maximum”. Under ADR 6.1.3.1 that figure is the maximum gross mass of the assembled package, inners included, so overfilling a box beyond its marked mass voids the test that the mark represents. The “S” that follows shows the packaging was tested for solids or for inner packagings. A single packaging for liquids replaces the “S” with the hydraulic test pressure in kilopascals, and the density figure may be omitted where it does not exceed 1.2.
Reading the mark element by element
ADR 6.1.3.1 sets the order and meaning of each element. Working through the transcript’s box mark, UN 4G/X5/S/18/MY/PB, the pieces read as follows.
| Position | Example | Meaning under ADR 6.1.3.1 |
|---|---|---|
| Symbol | UN in a circle | The packaging conforms to a tested design type |
| Packaging code | 4G | Type 4 (box), material G (fibreboard); see ADR 6.1.2 |
| Performance letter | X | Tested to Packing Group I level |
| Mass or density | 5 | Maximum gross mass 5 kg (combination) or relative density (single liquids) |
| Solids or pressure | S or 150 | “S” for solids or inner packagings; test pressure in kPa for liquids |
| Year | 18 | Last two digits of the year of manufacture |
| State | MY, F, GB | Distinguishing sign of the state that authorised the mark |
| Manufacturer | PB or VL823 | Manufacturer name or symbol assigned by the competent authority |
The packaging code is the part most drivers skim past, yet it tells you in two characters what the container is made of and what shape it takes.
| First numeral | Packaging kind | Letter | Material |
|---|---|---|---|
| 1 | Drum | A | Steel |
| 3 | Jerrican | B | Aluminium |
| 4 | Box | G | Fibreboard |
| 5 | Bag | H | Plastics |
| 6 | Composite packaging | D | Plywood |
The instructor’s “plastic Gilligan” is a plastics jerrican, code 3H1 or 3H2, and the plastic drum is 1H1 (non-removable head) or 1H2 (removable head). Plastics drums and jerricans of types 1H and 3H also carry the month of manufacture, because ADR 4.1.1.15 gives them a five-year service life from that date unless the competent authority allows otherwise.
What the mark does not tell a driver
The mark proves the design passed drop, stacking and leakproofness tests. It does not prove that this package was correctly filled, closed or chosen for the substance inside. Those are consignor duties, but the driver still needs a clean picture before departure.
- The consignor selects packaging against the packing instruction in ADR 4.1, not against the mark alone.
- Packages with a UN mark still count towards the 1.1.3.6 load-points threshold unless another exemption applies.
- Limited quantity packages under ADR 3.4 do not carry a UN mark at all; they carry the diamond LQ mark and package gross mass limits instead.
- A damaged, leaking or overfilled package must not be loaded, however sound the printed mark looks.
- The transport document under ADR 5.4.1 must still name the UN number, proper shipping name, class and packing group of the contents.
If a mark shows a letter lower than the packing group on the document, for example Z packaging carrying a Packing Group II substance, the package is non-compliant and the load stops there. Raise it with the consignor or the DGSA rather than assuming someone else checked it.
How ADR Driver Pro Fits Into This
Packaging marks sit inside the Packages route, one of the 6 driver routes in ADR Driver Pro described in the training routes guide. The 13 modules cover the core syllabus plus each hazard class, so the packing group of a Class 3 flammable or a Class 8 corrosive is revised alongside the packaging that carries it. The 8 quick reference sets include a packaging code and marking lookup, useful when a 4G, 1H1 or 3H2 mark needs decoding at the tailgate. The 5 calculators include the 1.1.3.6 load-points tool for working out whether those marked packages push a load over the threshold, and the 6 field tools sit alongside the load documents where they are needed. Of the 1820 revision questions in the app, 110 are free, so the packing group and packaging mark items can be tried before committing to the full bank.
