Dangerous Goods by Ocean: IMDG Classes, Documents and What Gets Rejected

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 (IMDG 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

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.

How the IMDG Code applies to US shipments

US hazardous materials regulations authorize shipments by vessel to follow the IMDG Code. Under 49 CFR 171.22, a shipment offered for transportation in accordance with the IMDG Code must conform to the Code and also to the applicable requirements of that subpart. A US export or import by sea is therefore checked against two rulebooks at once, and the stricter requirement wins.

What the shipper is responsible for

Classification, packing, marking, labelling and declaration are the shipper's obligations, not the carrier's. 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

The shipping description

The description on the shipping paper follows a fixed order under 49 CFR 172.202: the UN identification number, the proper shipping name, the hazard class and, where the material has one, the packing group. Each person who offers hazardous material for transportation also certifies on the shipping paper that it is offered in accordance with the regulations (49 CFR 172.204). A carrier cannot transport a hazardous material by vessel until that certificate has been received (49 CFR 176.27(a)).

The basic description appears in sequence with nothing interspersed, as in "UN 1760, Corrosive liquid, n.o.s., (Octanoyl chloride), 8, II". The same line also carries:

• the total quantity of hazardous material by mass or volume, with the unit, for example "200 kg";
• the number and type of packages, for example "12 drums";
• the technical name in parentheses for generic "n.o.s." entries (49 CFR 172.203(k));
• the words "Limited Quantity" or "Ltd Qty" for limited quantity shipments (172.203(b));
• the name of the component that makes the material a marine pollutant, in parentheses (172.203(l));
• "Poison-Inhalation Hazard" or "Toxic-Inhalation Hazard" plus the zone letter for materials poisonous by inhalation (172.203(m)).

The packing group is shown in Roman numerals, except for Class 1 explosives, self-reactive substances, Division 5.2 materials and entries that have no packing group, such as Class 7.

The container packing certificate

The person responsible for packing or loading a freight container with hazardous packages for a manned ocean vessel gives the vessel operator a signed container packing certificate when the shipment is offered for transportation (49 CFR 176.27(c)). The certificate states that the container is serviceable for the materials loaded, contains no incompatible goods and is properly marked, labeled or placarded. It states that the packages were inspected before loading, are not damaged, are properly marked and labeled, and are properly secured.

Training

Personnel involved must be trained. Under 49 CFR 172.704, a new hazmat employee completes the required training within 90 days after employment or a change in job function, and everyone repeats it at least once every three years. The employer keeps a training record for each employee covering the preceding three years, and keeps it for 90 days after the employee leaves the job. That requirement applies to the people who classify and document as much as to those who load.

Placards and marks

A freight container holding any quantity of hazardous material is placarded on each side and each end (49 CFR 172.504). A container with non-bulk packages from two or more categories that need different placards can carry a DANGEROUS placard in place of the separate ones. When 1,000 kg (2,205 lb) or more aggregate gross weight of one category is loaded at one loading facility, the placard for that category is also applied.

For vessel transport, a non-bulk package of a marine pollutant carries the marine pollutant mark. When the proper shipping name ends in "n.o.s." or is a generic entry, the package also carries the name of the component that makes the material a marine pollutant (49 CFR 172.322).

Segregation is why bookings get refused

Segregation under 49 CFR 176.83 applies to all cargo spaces, on deck and under deck, and to all cargo transport units. It is achieved by keeping set distances between incompatible materials, by steel bulkheads or decks between them, or by a combination of both. The general requirements between classes come from the segregation table, and a material can add its own requirement through the code numbers in column 10B of the hazardous materials table. Segregation is not required between materials of different classes that are the same substance varying only in water content, or between groups of substances that the regulation lists as compatible. The cargo spaces between segregated materials can hold other cargo that is not incompatible with them.

The code sets out which classes 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 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. For class 3 flammable liquids, 49 CFR 173.150(b) excepts limited quantities from labeling (outside air transport) and from specification packaging when they are packed in combination packagings that follow the section. The relief applies only where the hazardous materials table references the section for that specific material. Quantity thresholds per inner and outer packaging and specific marking apply, and the relief does not remove the obligation to classify correctly. A shipment qualifies as limited quantity by meeting those thresholds, not by being small.

Vehicles and batteries

A vehicle with an internal combustion engine, fuel cell or batteries is regulated cargo on a vessel. Under 49 CFR 176.905, each vehicle is inspected for leaks and electrical faults before loading, and a vehicle with either cannot be transported. A flammable-liquid tank is no more than one quarter full and the liquid does not exceed 250 L (66 gal). Lithium batteries installed in a vehicle must be of a type that passed the UN Manual of Tests and Criteria, and a damaged or defective battery is removed and shipped under the provisions for damaged batteries. See breakbulk vs container shipping for how vehicles are carried.

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.

On the vessel, the carrier and its agents prepare a dangerous cargo manifest, list or stowage plan, kept on or near the bridge, and it lists only materials subject to the hazardous materials regulations or the IMDG Code (49 CFR 176.30).

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. US regulations in 49 CFR 171.22 authorize shipments by vessel to follow it.

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?

Only when the segregation rules allow every combination in the container and the consolidator accepts the class. Many classes are excluded from consolidated loads, so the booking declares the hazard up front.

Do lithium batteries count as dangerous goods?

Yes, class 9, with separate provisions for batteries shipped alone, packed with equipment or installed in equipment. Installed batteries must be of a type that passed the UN Manual of Tests and Criteria.

What is a container packing certificate?

A signed statement that the container is serviceable, holds no incompatible goods, is marked, labeled or placarded and that the packages are inspected, undamaged and secured. The person who packed the container gives it to the vessel operator.

How often must hazmat employees be retrained?

At least once every three years, with initial training within 90 days of starting the job or changing function, under 49 CFR 172.704.

What does the dangerous goods shipping description contain?

The UN number, proper shipping name, hazard class and packing group, in that order, followed by the total quantity and the number and type of packages. Marine pollutant, limited quantity and inhalation hazard entries add words to the same line.

How is segregation achieved on board?

By set distances between incompatible materials, by steel bulkheads or decks between them, or by both, as 49 CFR 176.83 and the code's segregation table require.

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.