• Per the IMDG Code, labels on dangerous goods identify the primary and subsidiary hazards of the material, as well as additional marks or symbols indicating precautions for handling and storage.

Labeling requirements in the International Maritime Dangerous Goods (IMDG) Code address danger labels. Additional marks or symbols indicating precautions for handling or storing a package (such as a symbol indicating that a package must be kept dry) may be displayed on a package if appropriate.

Labels must identify primary and subsidiary hazards according to the models in IMDG Code Section 5.2.2.2.2, which define and illustrate requirements for:

• Class, Division, or Category;
• Symbol and symbol color;
• Background color;
• Figure in bottom corner and figure color; and
• Other required aspects for each label.

For articles or substances specifically listed in the Dangerous Goods List, a danger class label must be affixed as indicated in:

• Column 3,
• Column 4, and
• Column 6.

A package containing a dangerous substance with a low degree of danger may be exempt from the labeling requirements. In this case, column 6 of the Dangerous Goods List will specify that no hazard label is required.

If a substance that meets the definition of more than one class is not specifically listed by name in the Dangerous Goods List, the provisions in chapter 2.0 must be used to determine the primary hazard class of the goods. In addition to the label required for that primary hazard class, subsidiary hazard labels must also be applied as specified in the List. However:

• Packagings containing substances of class 8 need not bear subsidiary hazard label model No. 6.1 if the toxicity arises solely from the destructive effect on tissue; and
• Substances of class 4.2 need not bear subsidiary hazard label model No. 4.1.

Three separate labels are provided for class 2:

• Red for flammable gases of class 2.1;
• Green for non-flammable, non-toxic gases of class 2.2; and
• White for toxic gases of class 2.3.

Requirements for labels for class 2 gases with subsidiary hazards are defined in IMDG Code Section 5.2.2.1.4.

Label placement

Each label must be:

• Located on the same surface of the package near the proper shipping name mark;
• Placed on the packaging so that it is not covered or obscured; and
• Displayed next to each other when primary and subsidiary hazard labels are required.

If a package is an irregular shape or small size and a label cannot be satisfactorily affixed, the label may be attached to the package by a securely affixed tag or other suitable means.

A placement exception may apply to cylinders for class 2. Due to their shape, orientation, and securing mechanisms for transport, these may bear labels that have been reduced in size, according to ISO 7225:2005, Gas cylinders, Precautionary labels, and displayed on the shoulder of the cylinders. Labels may overlap to the extent provided for by ISO 7225:2005; however, in all cases, the labels representing the primary hazard and the numbers appearing on any label must remain fully visible and the symbols recognizable.

Note: When the diameter of the cylinder is too small to permit the display of the reduced size labels on the shoulder of the cylinder, the reduced sized labels may be displayed on the cylindrical part. Intermediate bulk containers of more than 450 L capacity and large packagings must be labeled on two opposing sides.

Labels must be affixed on a surface of contrasting color.

Special provisions

Special labeling provisions apply to certain substances and materials, including:

• Self-reactive substances,
• Organic peroxides,
• Infectious substances,
• Radioactive material, and
• Articles containing dangerous goods transported as UN Nos. 3537, 3538, 3539, 3540, 3541, 3542, 3543, 3544, 3545, 3546, 3547 and 3548.

Format of labels

Labels must comply with provisions in IMDG Code Section 5.2.2.2 in terms of color, symbols, numbers, and general format.

Labels must:

• Be displayed on a background of contrasting color, or
• Have either a dotted or solid outer boundary line.

The label must be a square set at an angle of 45 degrees (diamond-shaped). The minimum dimensions must be 100 mm × 100 mm.

If the size of the package necessitates, the dimensions may be reduced proportionally, provided the symbols and other elements of the label remain clearly visible. Dimensions for cylinders must comply with IMDG Code Section 5.2.2.2.

With few exceptions, the upper half of the label must contain the pictorial symbol and the lower half must contain the class number.

On labels other than those for material of class 7, the insertion of any text (other than the class or division number) in the space below the symbol must be confined to particulars indicating the nature of the hazard and precautions to be taken in handling.

The symbols, text, and numbers must be shown in black on all labels except for:

• The class 8 label, where the text (if any) and class number must appear in white;
• Labels with green, red, or blue backgrounds, where they may be shown in white;
• The class 5.2 label, where the symbol may be shown in white; and
• Class 2.1 labels displayed on cylinders and gas cartridges for liquefied petroleum gases, where they may be shown in the background color of the receptacle if adequate contrast is provided.

When affixing labels or applying stencils of labels on packages containing dangerous goods, the method must be such that the labels or stencils will still be identifiable on packages surviving at least three months immersed in the sea.