Packaging Technical Library › Hazmat Packaging › Drums · Document TL-001
Every UN-certified drum carries a coded mark that says what it was tested to carry. This guide decodes the mark on a 1A2 open-head steel drum certified for solids, field by field, and lists the rules to check before you fill one.
Example mark. Read it as: a steel open-head drum, tested for Packing Group II and III solids up to 400 kg gross, made in 2026, certified in the USA by registrant M1234, with a 1.2 mm body.
Reading the UN mark, field by field
| Field · example | What it means | |
|---|---|---|
| 1 | UN packaging symbolu/n | Certifies that the drum design passed UN performance tests. Embossed metal drums may show the capital letters “UN” instead of the circled symbol. |
| 2 | Packaging type code1A2 | 1 = drum · A = steel · 2 = removable head (open head). A 1A1 is the non-removable (tight-head) version. |
| 3 | Packing group ratingY | The highest hazard level the design was tested for: X = PG I, II and III · Y = PG II and III · Z = PG III only. |
| 4 | Maximum gross mass400 | For solids, the highest gross mass in kilograms (drum plus contents) the design was tested at. Do not exceed it. |
| 5 | Solids indicatorS | The drum is certified for solids or for inner packagings. It is not rated for liquids unless it carries a separate liquids mark. |
| 6 | Year of manufacture26 | The last two digits of the year the drum was made. |
| 7 | CountryUSA | The country (state) that authorized the mark, shown with its international vehicle registration code. |
| 8 | Manufacturer / certifierM1234 | The name or registered symbol of the manufacturer or approval agency. In the U.S., symbols are registered with PHMSA. |
| 9 | Metal thickness1.2 | Nominal body thickness in mm, required on metal drums meant for reuse or reconditioning. When the heads are thinner than the body, all three are shown as top–body–bottom, e.g. 1.0-1.2-1.0. |
Drum type codes
| Code | Drum |
|---|---|
1A1 | Steel, non-removable head (tight head) |
1A2 | Steel, removable head (open head) |
1B1 / 1B2 | Aluminum, non-removable / removable head |
1N1 / 1N2 | Other metal, non-removable / removable head |
1H1 / 1H2 | Plastic, non-removable / removable head |
1G | Fiber |
1D | Plywood |
Solids mark vs. liquids mark
Solids: 1A2/Y400/S/26/… — max gross mass (kg) + “S”.
Liquids: 1A2/Y1.4/150/26/… — max specific gravity + hydrostatic test pressure (kPa).
Marking rules to check
- Permanent on the bottom. Metal drums over 100 L must carry the mark on the bottom head in permanent form, such as embossing. A printed or labeled mark on the side or top is extra.
- Legible size. Characters at least 12 mm tall on packagings over 30 L or 30 kg, and at least 6 mm on those of 5 to 30 L.
- The rating is a ceiling. A
Ydrum may carry PG II or III material, never PG I. AnXdrum covers all three. - Stay at or under the tested mass. Contents plus drum must not exceed the marked kilograms.
- Close it as tested. The certification applies only with the closure (ring, bolt or lever lock and gasket) closed per the manufacturer’s instructions.
- Reconditioned drums carry an added mark with the reconditioner’s country, an
R(orRLif leakproofness-tested), and the reconditioner’s symbol.
Before you fill: a four-step check
X. PG II needs X or Y. PG III can use X, Y or Z.S mark, closed exactly as the maker’s instructions say.Frequently asked questions
What does 1A2 mean on a drum?
1A2 is the UN packaging code for a steel drum with a removable (open) head. The 1 means drum, A means steel and 2 means removable head. A 1A1 is a steel drum with a non-removable (tight) head.
What do X, Y and Z mean in a UN marking?
They give the packing groups the design was tested for. X covers Packing Groups I, II and III; Y covers II and III; Z covers III only.
What does the S mean in a UN drum marking?
S means the drum is certified for solids or inner packagings. The number before it is the maximum gross mass in kilograms.
Can an open-head drum marked for solids carry liquids?
Not on the strength of a solids mark. A drum must carry a liquids mark (specific gravity and hydrostatic test pressure) to be used for liquid hazardous materials.
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- How to Read UN Packaging Markings (Code Guide) · TL-004
- UN Markings: Tight-Head Steel Drums (Liquids) · TL-002
- IBC Tote UN Codes and Markings · TL-003
For reference only. This guide explains the marking format and does not replace the regulations or your packaging’s test report. Confirm against 49 CFR 178.503, 49 CFR 173.28 and the UN Recommendations on the Transport of Dangerous Goods, Model Regulations, Chapter 6.1. The mark shown is an example, not a real certification.