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Since 1987 taking the danger out of dangerous goods

The IMDG Code defines “segregation” as the process of separating two or more substances or articles which are considered mutually incompatible wen their packing or stowage together may result in undue hazards in case of leakage, spillage or any other accident. Segregation is obtained by maintaining certain distances between incompatible dangerous goods, by requiring the presence of one or more steel bulkheads or decks between them, or a combination of the previous methods.

Amendment 39-18 of the IMDG has updated once again the segregation provisions for the safe maritime transport of dangerous goods. The information is now displayed in a more comprehensible way, especially regarding segregation groups, and some provisions have been updated to better reflect our knowledge of how dangerous goods might dangerously interact with each other.  

Segregation in the IMDG Code is not only a matter of checking the general segregation requirements in the segregation table ( Even if two classes of dangerous goods are compatible in principle, there might be specific provisions that take precedence and dictate that two substances must be segregated. These specific provisions often mention segregation groups, which are families of dangerous goods that share certain similar chemical properties.

Each segregation group is now identified with an alphanumeric code, starting with the letters SGG. For example, SGG2 corresponds to ammonium compounds, while SGG18 indicates alkalis. Acids might be identified by two codes: SGG1, or SGG1a in the case of strong acids.


Segregation Group Code Segregation Group Description
SGG1 1 acids
SGG1a 1, entries marked * * identifies strong acids 
SGG2 2 ammonium compounds 
SGG3 3 bromates 
SGG4 4 chlorates 
SGG5 5 chlorites 
SGG6 6 cyanides 
SGG7 7 heavy metals and their salts (including their organometallic compounds) 
SGG8 8 hypochlorites 
SGG9 lead and its compounds 
SGG10 10  liquid halogenated hydrocarbons 
SGG11 11  mercury and mercury compounds 
SGG12 12  nitries and their mixtures 
SGG13 13  perchlorates 
SGG14 14  permanganates 
SGG15 15  powdered metals 
SGG16 16  peroxides 
SGG17 17  azides 
SGG18 18  alkalis 

The complete list of segregation groups can still be checked in paragraph of the IMDG Code, just like in previous editions of the Code.

However, the segregation group codes also appear in Column 16b of the Dangerous Goods List (if that article or substance has been identified as part of one of the segregation groups). They share this space with the segregation codes (used for the segregation special provisions tied to a specific substance or article), which all begin with the letters SG. When looking at Column 16b, now we need to pay attention and not confuse the two codes:

  • Segregation group codes: beginning by SGG, followed by a number.
  • Segregation codes: beginning by SG, followed by a number.

Column 16b

The meaning of the segregation codes can be consulted on 7.2.8. Many of them have been updated in the new amendment, and three new ones have been added, for a total of 78 codes.

Lastly, several substances or articles have been assigned new SG codes, effectively making their segregation requirements stricter. In particular, the codes SG35 (stow separated from SGG1 – acids), SG36 (stow separated from SGG18 – alkalis) and/or SG49 (stow separated from SGG6 – cyanides) have been added to many entries in the Dangerous Goods List.

2019 is a transition year, in which maritime transport of dangerous goods may follow the provisions of either the previous amendment (38-16) or the new one (39-18). Starting in 1 January 2020, only the new version will be valid, so the new segregation provisions will be mandatory.

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