The IMDG segregation table, in section 7.2.4 of the IMDG Code, shows the general segregation required between each pair of dangerous goods classes. Each cell holds a number from 1 to 4, which stands for a segregation term, or an “X”, which means you must check the Dangerous Goods List for specific provisions. This guide explains the terms, segregation groups, how to read the table and how to apply it, with two worked examples.
What segregation means under the IMDG Code
Segregation is the process of keeping apart substances or articles that are incompatible, so that leakage, spillage or another accident cannot cause them to react dangerously. Chapter 7.2 of the IMDG Code sets out the general segregation provisions. Later chapters in Part 7 apply them to particular ship types and cargo transport units, such as container ships, ro-ro ships and general cargo ships.
Segregation works in layers:
- The segregation table (7.2.4): general requirements between classes.
- The Dangerous Goods List, column 16b: substance-specific segregation codes, which take precedence over the general table where they conflict.
- The knowledge of the shipper and carrier: the chemical properties of the goods actually being shipped.
The four segregation terms
The table uses four terms, numbered from least to most strict:
| Number | Segregation term | In practice |
|---|---|---|
| 1 | “Away from” | Effectively segregated so the goods cannot interact dangerously in an accident, but they may be carried in the same compartment, hold or on deck. A minimum horizontal separation of 3 metres applies. |
| 2 | “Separated from” | In different compartments or holds when stowed under deck. On deck, a minimum horizontal separation of 6 metres applies. |
| 3 | “Separated by a complete compartment or hold from” | At least one complete compartment or hold between the goods, either vertically or horizontally. |
| 4 | “Separated longitudinally by an intervening complete compartment or hold from” | The strictest term. Vertical separation alone is not enough: there must be an intervening complete compartment or hold fore and aft. |
One rule applies to all four: any number in the table means the two classes cannot be packed in the same cargo transport unit (CTU), such as a container.
How to read the segregation table
To find the segregation between two classes, find the row for one class and the column for the other. Where they meet, you will see one of the following:
- 1, 2, 3 or 4: the segregation term shown above.
- X: the Dangerous Goods List must be consulted to check whether there are specific segregation provisions. X does not mean “no segregation required”.
- *: segregation between class 1 substances or articles is covered by separate provisions in chapter 7.2.
The table also requires you to take account of a single subsidiary hazard label. A substance with a subsidiary hazard must be segregated for that hazard as well as its primary class.
The table below is an extract showing a few common classes. Always use the full table in the edition of the Code you are applying.
| Class | 2.1 | 3 | 4.3 | 5.1 | 6.1 | 8 |
|---|---|---|---|---|---|---|
| 2.1 Flammable gases | X | 2 | 2 | 2 | X | 1 |
| 3 Flammable liquids | 2 | X | 2 | 2 | X | X |
| 4.3 Dangerous when wet | 2 | 2 | X | 2 | X | 1 |
| 5.1 Oxidizing substances | 2 | 2 | 2 | X | 1 | 2 |
| 6.1 Toxic substances | X | X | X | 1 | X | X |
| 8 Corrosive substances | 1 | X | 1 | 2 | X | X |
Segregation groups
The class alone does not capture every incompatibility. Two class 8 substances, an acid and an alkali, have the same class but can react violently with each other. To deal with this, the IMDG Code groups dangerous goods with similar chemical properties into 18 segregation groups:
- Acids
- Ammonium compounds
- Bromates
- Chlorates
- Chlorites
- Cyanides
- Heavy metals and their salts (including their organometallic compounds)
- Hypochlorites
- Lead and its compounds
- Liquid halogenated hydrocarbons
- Mercury and mercury compounds
- Nitrites and their mixtures
- Perchlorates
- Permanganates
- Powdered metals
- Peroxides
- Azides
- Alkalis
Where a segregation code in column 16b refers to a group, such as “away from acids”, it applies to every entry allocated to that group. The entries allocated to each group are listed in chapter 3.1, and the Dangerous Goods List shows each entry’s group as an SGG code (for example SGG1 for acids).
Not every substance in a chemical family is named in the Code. Many are shipped under N.O.S. (“not otherwise specified”) entries. In those cases the consignor must decide whether the goods belong in a segregation group and, if so, state this in the transport document.
Worked examples
These examples show how to apply the general table. In real shipments, always check column 16b of the Dangerous Goods List for each UN number, because specific provisions take precedence.
Example 1: A flammable liquid and an oxidizer
A shipper wants to load a class 3 flammable liquid and a class 5.1 oxidizing substance, neither with a subsidiary hazard, on the same container ship.
- Find the row for class 3 and the column for class 5.1. The cell shows 2.
- 2 means “separated from”.
- Because the cell holds a number, the two cannot be packed in the same container.
- Apply the container ship provisions for “separated from” to plan where each container goes on board.
- Check column 16b for each entry for any additional or stricter requirements.
Example 2: A substance with a subsidiary hazard
A class 3 flammable liquid with a class 8 subsidiary hazard is to be shipped with a class 4.3 substance, which emits flammable gas in contact with water.
- Primary hazard: class 3 against class 4.3 gives 2 (“separated from”).
- Subsidiary hazard: class 8 against class 4.3 gives 1 (“away from”).
- Apply the stricter of the two: “separated from”.
- Check column 16b for both entries, and any segregation group, before finalising the stowage plan.
How Hazcheck can help
Checking segregation by hand across a full stowage plan is slow and easy to get wrong. Hazcheck Validate and Hazcheck Validate Desktop check dangerous goods bookings against the IMDG Code, including segregation. Hazcheck Detect screens cargo descriptions to find dangerous goods that may have been misdeclared, which would otherwise escape segregation checks entirely. For staff who need to understand the rules, our IMDG Code e-learning covers segregation in depth, and the IMDG Code e-Reader gives quick access to chapter 7.2. Contact us to find out more.
Frequently asked questions
Where is the segregation table in the IMDG Code?
The segregation table is in section 7.2.4, in chapter 7.2 (general segregation provisions) of Volume 1.
What does “X” mean in the IMDG segregation table?
X means the Dangerous Goods List must be consulted to check whether there are specific segregation provisions for the entries concerned. It is not a blanket permission to stow the goods together.
What is the difference between “away from” and “separated from”?
Goods that are “away from” each other may be carried in the same compartment or hold, provided they are kept a minimum distance apart. Goods that are “separated from” each other must be in different compartments or holds when stowed under deck, with a greater distance on deck.
Can goods requiring “away from” be packed in the same container?
No. Any of the four segregation terms means the goods cannot be packed in the same cargo transport unit.
Does the Dangerous Goods List override the segregation table?
Yes. Where the specific provisions in column 16b of the Dangerous Goods List conflict with the general table, the specific provisions take precedence.
Do I need to segregate for subsidiary hazards?
Yes. Segregation must take account of a single subsidiary hazard label as well as the primary class, and the stricter requirement applies.
Sources
- Estonian Transport Administration: IMDG Code 37-14 extract, Part 7 stowage and segregation (7.2.4 segregation table, 7.2.5 segregation groups, 7.2.8 segregation codes)
- IMO: Dangerous goods (IMDG Code overview)
- The Compliance Center: Segregating dangerous goods under the IMDG Code
- Shashi Kallada: How to apply IMDG Code segregation rules