UN packaging codes, field by field

On the base of a jerrican or the side of a box you will often find a string like 4G/Y145/S/02, with a small u over n in a circle in front of it. That is the UN packaging mark. It tells you which design type passed testing, what the packaging is fit to carry and who made it. Once you know the order of the fields, you can read it in a few seconds. Below we take it apart piece by piece, using the examples ADR itself prints in 6.1.3.11.

What the mark is made of

As a rule, dangerous goods may only travel in packagings whose design type has passed testing (ADR 4.1.1.3.1). The mark is the proof. It has to be durable, legible and easy to see. On a package with a gross mass over 30 kg it goes on the top or a side (ADR 6.1.3.1).

The elements always come in the same order, separated by a slash or a space (ADR 6.1.3.7):

1. (a) the UN packaging symbol. Embossed metal packagings may show the letters "UN" instead.
2. (b) the code for the type of packaging, such as 4G or 1A1.
3. (c) a letter for the packing groups (X, Y or Z), followed by the maximum gross mass in kg or, for liquids, the relative density.
4. (d) an "S" for solids and inner packagings or, for liquids, the test pressure in kPa.
5. (e) the last two digits of the year of manufacture.
6. (f) the State that authorised the mark, shown by its distinguishing sign for vehicles in international road traffic.
7. (g) the manufacturer's name or another identification set by the competent authority.

Characters are at least 12 mm high, or at least 6 mm on packagings of 30 litres or 30 kg net or less. On packagings of 5 litres or 5 kg net or less they only need to be of a suitable size (ADR 6.1.3.1). The mark can run over one line or several, as long as the order is kept (ADR 6.1.3.13, Note).

The type code: number, letter, number

The packaging type code starts with a number for the kind of packaging. A capital letter for the material follows, then, where needed, a second number for the category within that kind (ADR 6.1.2.1).

• Kind (first number): 1 drum, 3 jerrican, 4 box, 5 bag, 6 composite packaging, 0 light gauge metal packaging. Numbers 2 and 7 are reserved (ADR 6.1.2.5).
• Material (letter): 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 (ADR 6.1.2.6).

For drums and jerricans the last number separates two designs. 1A1 is a steel drum with a non-removable head, 1A2 one with a removable head. 3H1 is a plastics jerrican with a non-removable head (ADR 6.1.2.7).

• Composite packagings have two letters: first the inner receptacle, then the outer packaging. 6HA1 is a plastics receptacle in a steel drum (ADR 6.1.2.2 and 6.1.2.7).
• Combination packagings, meaning inner packagings inside an outer one, carry only the code of the outer packaging (ADR 6.1.2.3).
• T, V or W after the code: T marks a salvage packaging, V a special packaging, and W a packaging made to a different specification that still counts as equivalent (ADR 6.1.2.4).

Example 1: a fibreboard box for solids

For a new fibreboard box, ADR gives this mark (ADR 6.1.3.11):

4G/Y145/S/02 NL/VL823

Part	Meaning
4G	box (4) made of fibreboard (G)
Y	tested for packing groups II and III
145	maximum gross mass 145 kg
S	for solids or inner packagings
02	made in 2002
NL	mark authorised in the Netherlands
VL823	manufacturer or authority identification (only an example in ADR)

The packing group letter decides what can go inside. X covers packing groups I, II and III, Y covers II and III, and Z covers III only (ADR 6.1.3.1 (c)). A packing group II substance can therefore go in an X or a Y packaging, but never in a Z.

Example 2: a steel drum for liquids

For a new steel drum carrying liquids, the ADR example reads (ADR 6.1.3.11):

1A1/Y1.4/150/98 NL/VL824

Part	Meaning
1A1	drum (1) made of steel (A) with a non-removable head (1)
Y	tested for packing groups II and III
1.4	tested for a relative density of 1.4
150	test pressure 150 kPa
98	made in 1998
NL/VL824	State and manufacturer, as in the first example

The density only appears on packagings without inner packagings that are meant for liquids. If it is 1.2 or less, it can be left out. The test pressure is rounded down to the nearest 10 kPa (ADR 6.1.3.1 (c) and (d)). That is why the ADR example for a remanufactured steel drum reads 1A2/Y/100/01 USA/MM5. There is no density after the Y, and 100 is the test pressure in kPa.

Plastics drums and jerricans (1H and 3H) also show the month of manufacture. It may sit away from the rest of the mark, and the usual way is a small clock symbol (ADR 6.1.3.1 (e)).

Reconditioned, REC and multiple marks

• Reconditioned packagings: after reconditioning, the reconditioner adds the State, their name or identification, the year and the letter "R". If the packaging has passed the leakproofness test, an "L" follows (ADR 6.1.3.8). ADR example: 1A1/Y1.4/150/97 NL/RB/01 RL (ADR 6.1.3.12).
• REC: packagings made from recycled plastics material carry "REC" next to the mark (ADR 6.1.3.10).
• RID/ADR instead of UN: this symbol goes on composite packagings of glass, porcelain or stoneware and on light gauge metal packagings that meet simplified conditions. They are approved for rail, road and inland waterway carriage (ADR 6.1.3.1 (a) (ii)).
• More than one mark: a packaging that meets several tested design types may carry several marks. They must sit close together and each must be shown in full (ADR 6.1.3.14).

IBCs and large packagings carry a similar mark that adds the month and year of manufacture, the stacking test load and the maximum permissible gross mass (ADR 6.5.2.1.1 and 6.6.3.1).

For limited quantities, the tested design type requirement does not apply. For packagings, only the general construction rules in 6.1.4 still apply (ADR 3.4.1). An LQ carton therefore needs no UN mark.

Put it into practice

The UN mark says nothing about what is inside. The UN number and the danger labels do that. Next time you load, read the codes on the jerricans and drums in order: kind, material, X/Y/Z, mass or density, S or pressure, year.

In the free test you get an explanation and the ADR reference after every answer. The app has the full syllabus.

Sources

ADR 2025 (UNECE English text): 4.1.1.3.1, section 6.1.2 (6.1.2.1 to 6.1.2.7), section 6.1.3 (6.1.3.1, 6.1.3.7, 6.1.3.8, 6.1.3.10 to 6.1.3.14), 6.5.2.1.1, 6.6.3.1 and 3.4.1. The codes in the examples come from 6.1.3.11 and 6.1.3.12. In Great Britain, ADR applies through the Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations 2009. This guide explains the basics. For an actual consignment, the wording of ADR is what counts.