Hazardous cargo moves by sea every day without incident, and the reason is a rulebook that leaves very little to interpretation. The International Maritime Dangerous Goods Code governs classification, packing, marking, documentation and segregation. Working inside it is straightforward. Working around it is how shipments get refused, fined or worse.
The nine classes
| Class | Covers |
|---|---|
| 1 | Explosives |
| 2 | Gases, flammable, non-flammable and toxic |
| 3 | Flammable liquids |
| 4 | Flammable solids and substances liable to spontaneous combustion |
| 5 | Oxidising substances and organic peroxides |
| 6 | Toxic and infectious substances |
| 7 | Radioactive material |
| 8 | Corrosives |
| 9 | Miscellaneous, including lithium batteries and environmentally hazardous substances |
Every substance has a UN number and a proper shipping name, and those two identify it in every language and in every filing. Gasoline is UN 1203. Paint is UN 1263. Lithium ion batteries fall in class 9 with their own detailed provisions.
What the shipper is responsible for
Classification, packing, marking, labelling and declaration are the shipper's obligations, not the carrier's. In practice that means:
- Obtaining a current safety data sheet and classifying from it
- Using UN specification packaging where required, within its permitted period of use
- Marking and labelling every package with the UN number, proper shipping name and hazard labels
- Placarding the container
- Issuing a dangerous goods declaration
- Issuing a container packing certificate confirming the container was loaded in accordance with the code
Personnel involved must be trained. That requirement applies to the people who classify and document as much as to those who load.
Segregation is why bookings get refused
The code sets out which classes may travel together and how far apart. A consolidator running mixed LCL cargo has to satisfy those rules for every combination in the box, which is why many consolidators refuse certain classes outright and why hazardous cargo is often better suited to a full container. Declare it at booking, not at the warehouse. Undeclared hazardous cargo discovered during loading gets the whole container refused, and the shipper carries the cost.
Limited quantities and excepted quantities
Small packages of some substances qualify for reduced requirements under limited quantity or excepted quantity provisions. The relief is real but narrow: quantity thresholds per inner and outer packaging, specific marking, and it does not remove the obligation to classify correctly. Treating a shipment as limited quantity because it is small is not the same as qualifying.
Documentation that travels with the cargo
The dangerous goods declaration, the container packing certificate, and the safety data sheet. These pair with the commercial invoice and packing list, and the descriptions have to agree across all of them. The manifest description also has to reflect the hazard, which links back to AMS filing.
What gets shipments rejected
Expired or reused UN packaging. Labels applied over old labels. A safety data sheet in the wrong language for the destination. A declaration signed by someone untrained. Marine pollutant marking omitted on substances that require it. Batteries shipped inside equipment without the provisions that apply. Every one of these is discovered at the gate, when the truck is already there.
FAQ
What is the IMDG Code?
The International Maritime Dangerous Goods Code, the framework governing the carriage of hazardous cargo by sea.
Who classifies dangerous goods?
The shipper, using the safety data sheet. Carriers and forwarders verify documentation but do not assume responsibility for classification.
Can dangerous goods be consolidated with general cargo?
Sometimes, subject to segregation rules and the consolidator's policy. Many classes are excluded from consolidated loads.
Do lithium batteries count as dangerous goods?
Yes, class 9, with detailed provisions depending on whether they ship alone, with equipment or inside equipment.
What is a container packing certificate?
A signed statement that the container was loaded in accordance with the code, including segregation, securing and placarding.
Shipping hazardous cargo into the Caribbean or Latin America? Send us the UN numbers and the safety data sheets and we will confirm what the lane accepts.