How do IMDG classes relate to UN dangerous goods classes?

The IMO adopted the United Nations dangerous goods class system, so the class numbers are the same. An IMDG Class 3 substance is also UN Class 3. The IMDG Code adds maritime-specific detail such as divisions, packing groups, and segregation rules for carriage by sea.

What are the nine main dangerous goods classes?

Class 1 explosives, Class 2 gases, Class 3 flammable liquids, Class 4 flammable solids and reactive substances, Class 5 oxidisers and organic peroxides, Class 6 toxic and infectious substances, Class 7 radioactive material, Class 8 corrosives, and Class 9 miscellaneous dangerous substances and articles.

What do the division numbers like 2.1 or 4.3 mean?

Some classes are split into divisions for more specific hazards. Class 2 divides into 2.1 flammable gas, 2.2 non-flammable non-toxic gas, and 2.3 toxic gas. Class 4 divides into 4.1 flammable solids, 4.2 spontaneously combustible, and 4.3 dangerous when wet.

What is the difference between IMCO and IMO?

IMCO, the Inter-Governmental Maritime Consultative Organization, was the former name of the body now called the IMO, the International Maritime Organization. The IMDG Code is its set of rules for carrying dangerous goods by sea, so IMCO class and IMDG class refer to the same scheme.

Which class covers lithium batteries?

Lithium batteries are assigned to Class 9, miscellaneous dangerous goods. Class 9 covers substances and articles that present a danger during transport not covered by the other classes, which also includes dry ice, marine pollutants, and asbestos.

IMDG / IMO Class to UN Class Cross-Reference

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Mapping IMDG classes to UN classes

When dangerous goods move by sea they are regulated by the IMO’s IMDG Code, but the hazard classes themselves come from the United Nations dangerous goods system. This reference cross-references each IMDG class and division to its UN class number, with the hazard name and example substances, so you can confirm the class for a cargo or read a shipping document.

How it works

The key fact is that the class numbers are shared:

IMDG Class 3   ==  UN Class 3   (flammable liquids)
IMDG Class 4.3 ==  UN Class 4   (dangerous when wet)
IMDG Class 8   ==  UN Class 8   (corrosives)

The IMO adopted the UN class scheme, so there is no renumbering between the two; the class digit is identical. What the IMDG Code adds on top is maritime detail: the explosive divisions 1.1 to 1.6, packing groups I to III for the degree of danger, and segregation tables saying which classes must be stowed apart on board. Divisions such as 2.1, 2.2, 2.3 or 4.1, 4.2, 4.3 refine the broad class into specific hazards.

Tips and notes

The older abbreviation IMCO refers to the former name of the IMO and describes the same class scheme, so an IMCO class label is just an IMDG class. For a given substance the authoritative source is its UN number and proper shipping name in the dangerous goods list, which fixes the class, division, and packing group together. Marine pollutants and lithium batteries both fall under the catch-all Class 9.