Hazard identification numbers utilized under European and some South American regulations, may be found in the top half of an orange panel on some intermodal bulk containers. The United Nations 4-digit identification number is in the bottom half of the orange panel.

The hazard identification number in the top half of the orange panel consists of two or three digits. In general, the digits indicate the following hazards:

2 - Emission of gas due to pressure or chemical reaction

3 - Flammability of liquids (vapors) and gases or self-heating liquid

4 - Flammability of solids or self-heating solid

5 - Oxidizing (fire-intensifying) effect

6 - Toxicity or risk of infection

7 - Radioactivity

8 - Corrosivity

9 - Risk of spontaneous violent reaction

NOTE: The risk of spontaneous violent reaction within the meaning of digit 9 include the possibility, due to the nature of a substance, of a risk of explosion, disintegration and polymerization reaction followed by the release of considerable heat or flammable and/or toxic gases.

• Doubling of a digit indicates an intensification of that particular hazard (i.e., 33, 66, 88).
• Where the hazard associated with a substance can be adequately indicated by a single digit, the digit is followed by a zero (i.e., 30, 40, 50).
• A hazard identification number prefixed by the letter "X" indicates that the substance will react dangerously with water (i.e., X88).