The CAS Number (CAS = Chemical Abstract Service) is used for identification of chemical substances. It is composed of numbers and dashes, and is structured as follows:

1. Sequence of digits with up to 7 digits
2. Dash
3. Sequence of exactly 2 digits
4. Dash
5. Check digit

Examples:

• 67-64-1 → Acetone
• 7440-17-7 → Rubidium
• 7647-01-0 → Hydrochloric acid

The class, also called hazard class, describes the dangers that can arise from a substance or object. The hazard classes range from 1 to 9. In IMDG there is also the value MHB.

A complete list of classes with their respective meaning can be found in the table below.

The classification code characterizes the dangerous properties of a substance or article, e.g. toxic (T) or flammable (F). These properties can also occur in combination, e.g. toxic and corrosive (TC).
For substances or articles in class 1, the classification code is made up of the subclass and compatibility group, e.g. 1.1F. For substances or articles in class 2, the code consists of a number and one or more letters representing the group of dangerous properties.

A complete list of classification codes with their respective meaning can be found in the table below.

The EC Number (EC = European Community) is an ordering criterion in the European chemicals legislation (REACH Regulation). It consists of 7 digits and dashes, and is constructed as follows:

1. Sequence of exactly 3 digits
2. Dash
3. Sequence of exactly 3 digits
4. Dash
5. 1 digit

Examples:

• 200-001-8 → Formaldehyde
• 200-659-6 → Methanol
• 231-126-6 → Rubidium

The hazard identification number (also known as HIN or Kemler number) is a number used to identify the dangers posed by a dangerous good and is placed on the orange plate above the UN number.

A complete list of hazard identification numbers with their respective meanings can be found in the table below.

The packing group divides the dangerous goods of certain classes according to their degree of danger. There are three different packing groups:

Transport units carrying dangerous goods shall display two rectangular orange-coloured plates conforming to 5.3.2.2.1, set in a vertical plane. They shall be affixed one at the front and the other at the rear of the transport unit, both perpendicular to the longitudinal axis of the transport unit. They shall be clearly visible.

The orange plate shows the hazard identification number at the top and the UN number at the bottom.

The UN number is a four-digit number to identify substances or objects in accordance to the UN Recommendations on the transport of dangerous goods. An UN number is assigned to each hazardous material in the dangerous goods lists of the regulations of all modes of transport.
Examples of UN numbers:

• 0004 → AMMONIUM PICRATE
• 0312 → CARTRIDGES, SIGNAL
• 2465 → DICHLOROISOCYANURIC ACID SALTS
• 3077 → ENVIRONMENTALLY HAZARDOUS SUBSTANCE, SOLID, N.O.S.

The terms ID number or substance number include additional numbers that are not regular UN numbers. They have been introduced for identification of certain substances or objects by transport regulations. ICAO includes ID numbers from 8000 and greater. ADN includes substance numbers from 9000 and greater.