What are "segregation groups" and how are they applied to "N.O.S." entries?

Modified on Fri, 09 Sep 2022 at 10:28 PM

"Segregation groups" are defined as dangerous goods with similar chemical properties. There are 18 segregation groups defined in the IMDG Code as listed at

Grouping dangerous goods entries together in this way provides an additional layer of regulation to occur for the segregation of dangerous goods, both within a Cargo Transport Unit (CTU) and on the vessel itself.

Segregation groups are unique to the IMDG Code and for named entries are assigned in Column 16 of the IMDG Code Dangerous Goods List.

Incompatible entries can then be identified as requiring specific segregation from a certain group of substances. For example, acids (segregation group 1 - SGG1), generally, require segregation from alkalis (SGG 18).

So far so good? Yes. But life is never that straightforward. Where it becomes complicated is the application of segregation groups to "N.O.S." - Not Otherwise Specified entries. This is required by the IMDG Code at However, it is stated in the regulation in such a way, as to require a decision to be made by the consignor (to whom the legal obligation exists via this provision) to assign a segregation group, if required, to a N.O.S. entry.

This starts to make the requirement open to interpretation, with no guidance or rule on when a segregation group should be applied.

Where issues seem to arise currently with dangerous goods acceptance, is that if no assignment is made, this is not made clear, because it is not required to be. 

Therefore a shipping line does not know whether assignment has been considered, but then rejected by the consignor as not applicable (and therefore deliberately not mentioned), or has been overlooked and not mentioned by mistake or ignorance of the provisions, which could lead to incompatible goods being loaded together. 

This often leads to the rejection of DGNs (Dangerous Goods Notes - the dangerous goods transport document including the shipper's declaration and packing certificate used for sea transport).

The consignor therefore needs to complete three steps for a N.O.S. entry:

1. Decide whether or not their goods, which may be a complicated mixture, should be assigned to a segregation group.

2. Decide which segregation group is applicable.

3. Mention this in the DGN, in accordance with IMDG using the text "IMDG Code segregation group 1 - acids" for example.

It is our advice that, in some circumstances the consignor needs to consider and implement a fourth step:

4. If the decision is made that no segregation group is applicable, especially for N.O.S. entries of Class 8, either mention this in the transport document, e.g., "segregation group not applicable" which is completely valid in some circumstances (such as a product mixture classified as corrosive by default using a summation method, but where the components effectively neutralise each other), or, inform your forwarder of this, so that they may include direction to the shipping line when seeking acceptance. 

This will therefore stop your DGN being rejected and save a lot of time for all parties involved, which in today's logistics environment, may involve a considerable chain of people before the DGN meets the shipping line. Who subsequently all have to pass the DGN back to the one before, like a game of "pass the parcel" but with a DGN, and typically with the loss of explanation somewhere along the chain.

Please remember that if you are shipping dangerous goods, you are required to have had the relevant training. We offer a full IMDG Code online training course, available at: https://www.dangerousgoodstrainingonline.com 

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