IMDG Code Quick Reference for Marine Shippers

The International Maritime Dangerous Goods Code (IMDG Code) is the IMO instrument that governs dangerous goods carried by sea. It is published by the IMO in two volumes plus a Supplement and is updated on a two-year cycle (Amendment 41-22 was the previous edition; Amendment 42-24 is the current one for 2026). This is a quick field reference, not a substitute for the Code itself.

Structure of the IMDG Code

• Volume 1 — Parts 1, 2 and 4–7. General provisions, classification, packing, consignment procedures, container traffic, ship operations.
• Volume 2 — Part 3 (Dangerous Goods List, limited and excepted quantities, special provisions) and the appendices.
• Supplement — EmS (Emergency Schedules), MFAG (Medical First Aid Guide), reporting procedures, IMO/ILO/UNECE Code of Practice for packing CTUs, and the INF Code.

The Dangerous Goods List

Located in Chapter 3.2. Use it the same way you would the IATA DGL — find the proper shipping name, read the class, packing group, subsidiary risks, packing instructions, IBC and tank instructions, special provisions, limited quantities, EmS reference and stowage and segregation entries. The IMDG DGL is denser than the IATA equivalent because it carries the EmS / segregation columns.

Segregation

The segregation table in chapter 7.2 gives the rule for stowing incompatible goods together on a ship. The codes you will see constantly:

• 1 — Away from: at least 3 m apart in the same compartment.
• 2 — Separated from: in different compartments / holds.
• 3 — Separated by a complete compartment or hold from.
• 4 — Separated longitudinally by an intervening complete compartment or hold from.
• X — No general segregation; refer to DGL.

Segregation rules are looser on deck than under deck and looser between closed CTUs than between open ones. The standard CTU-to-CTU rules in 7.2.4 are what most freight forwarders consult.

Marine pollutants

A substance is a marine pollutant when listed in 2.10.3 of the Code or, by UN criteria, when it is acutely or chronically toxic to aquatic life and meets the GHS H400/H410/H411 criteria. Marine pollutants must be marked with the dead-fish-and-tree symbol on packages and CTUs, and they must be declared as such on the Dangerous Goods Declaration. UN3077 (solid) and UN3082 (liquid) are the generic entries for environmentally hazardous substances.

Container Packing Certificate

For any DG carried in a CTU (container, swap body, vehicle), the person responsible for packing must issue a Container/Vehicle Packing Certificate (CPC) under section 5.4.2 of the Code. It declares that:

• The CTU was clean, dry and fit for purpose.
• Goods authorised to be stowed together were so stowed.
• Packages were inspected for damage and only sound packages loaded.
• Drums are upright.
• All packages are properly secured and braced.
• The unit and packages are properly marked, labelled and placarded.

Documents you carry

1. Dangerous Goods Declaration (DGD) — section 5.4.1 form, with UN number, PSN, class, PG, packing group, marine pollutant flag, EmS reference, flashpoint where applicable.
2. Container Packing Certificate — section 5.4.2.
3. Bill of lading — references the DG declaration and the EmS schedule.
4. For limited quantities (LQ): the LQ mark on the package and the LQ statement in the DGD.

Stowage categories A–E

Stowage category determines whether the package or CTU may be carried on deck only, under deck only, or anywhere. Categories A and B generally allow both; C and D restrict carriage; E is the most restrictive and applies primarily to certain explosives. Always confirm the stowage category from the DGL before booking.

EmS — Emergency Schedules

The EmS Guide in the Supplement gives the master with a fire and spill response procedure for the substance, indexed by an F-letter and an S-letter (e.g. F-A, S-Q). The EmS reference appears in the DGL and on the DGD.

Limited and excepted quantities

Limited Quantities (LQ) and Excepted Quantities (EQ) provide reduced burden for small inner packagings of low-risk DG. For sea transport, LQ shipments still require an LQ-marked package and a DGD with the LQ statement, but they are exempt from many marking, labelling and segregation requirements.

For broader background on UN numbers, classes and packing groups across all modes, see our complete guide to UN numbers and hazard classes. If your shipment includes lithium batteries, head to the lithium battery shipping guide.