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The law · International

IMDG Code — dangerous goods by sea

International Maritime Dangerous Goods Code, IMO, mandatory under SOLAS Chapter VII and MARPOL Annex III

Last review · August 26, 2026

What it is

The IMDG Code is the IMO’s code for the carriage of dangerous goods by sea in packaged form: classification, packing, marking, labelling, placarding, documentation, stowage and segregation on board.

It is mandatory under SOLAS chapter VII and MARPOL Annex III, and it is amended every two years, with a one-year voluntary period before each amendment becomes compulsory.

Where it applies

Every ship flying the flag of a SOLAS state, which is nearly all international shipping, and every port that loads dangerous goods in packaged form.

What to know

  1. 01The same nine classes and UN numbers as the ADR and the IATA DGR, so a multimodal shipment keeps one classification along the chain.
  2. 02The Dangerous Goods List gives, for each UN number, the packing group, packing instructions, stowage category and segregation group.
  3. 03Segregation keeps incompatible classes apart on board and inside a container; the container packing certificate attests it was done.
  4. 04The shipper’s dangerous goods declaration and the container packing certificate must reach the carrier before loading.
  5. 05Marine pollutants carry an additional mark and are governed by MARPOL Annex III.
  6. 06Chapter 1.3 requires training for shore-side personnel involved in dangerous goods by sea.

Who needs to know it

  • Shippers and forwarders booking dangerous goods in containers.
  • Container packers, who sign the packing certificate.
  • Dangerous goods and air/sea students: IMDG is an examined block.

An informative summary, not legal advice. Always check the current text of the rule before deciding.