Stowage and Segregation of Dangerous Goods on Container Ships

Stowage of dangerous goods on board container ships are decided by two factors, Document of Compliance and IMDG Code. IMDG Code sets forth the Stowage and Segregation Rules which is executed on each vessel according to the Document of Compliance issued to her. Document of Compliance is issued to a vessel if it meets the requirements of SOLAS Regulation II-2/19, Construction – Fire protection, fire detection and fire extinction (Carriage of Dangerous Goods).

The Document of Compliance certifies that the construction and equipment of the mentioned ship have been found to comply with the provisions of regulation II-2/19 of the International Convention for the Safety of Life at Sea, 1974, as amended; and that the ship is suitable for the carriage of those classes of dangerous goods as specified in the appendix thereto, subject to any provisions in the International Maritime Dangerous Goods (IMDG) Code and the International Maritime Solid Bulk Cargoes (IMSBC) Code for individual substances, materials or articles also being complied with.

ISO Tanks loaded on Vessel
ISO Tanks loaded on Vessel- Photo Courtesy Ashwin Kakkadan 2nd Mate

In this document the under deck spaces and on deck spaces are marked separately for carriage of Packaged Dangerous Goods, Bulk Goods and what is not permitted.

Validity of the document of compliance will not exceed 5 years and will not be extended beyond the expiry date of the valid Cargo Ship Safety Construction Certificate issued to the ship concerned under the provisions of SOLAS regulation I/12. See Maritime Safety Committee Circular MSC.1/Circ.1266 for full details.

Coming to IMDG Code stowage and Segregation rules for dangerous goods vessels are categorized into two types, Cargo Ships and Passenger Ships. This categorization further divides cargo ships and passenger ships for carriage of Class 1, Explosives, and Classes 2 to 9. The differentiation is for Class 1, Explosives, Cargo ships (up to 12 passengers) and Passenger ships. For Classes 2-9 Cargo ships or passenger ships carrying a number of passengers limited to not more than 25 or to 1 passenger per 3 m of overall length, whichever is the greater number and Other passenger ships in which the limiting number of passengers transported is exceeded.

Stowage categories for Explosives (Class 1) – IMDG Code 36-12
Stowage categories for Explosives (Class 1) – IMDG Code 36-12

For other than class 1 (Explosives) each dangerous goods listed in IMDG Code 36th Amendment, Dangerous Goods List column 16 specifies stowage requirement. This is indicated by Category A, B, C, D or E.

On Deck only stowage is always prescribed for cases where:

  1. constant supervision is required; or
  2. accessibility is particularly required; or
  3. there is a substantial risk of formation of explosive gas mixtures, development of highly toxic vapours, or unobserved corrosion of the ship

Below dangerous goods when permitted to be loaded under deck by IMDG Code will additionally require mechanical ventilation for the cargo hold.

  • class 2.1;
  • class 3 with a flash point of less than 23°C c.c.;
  • class 4.3;
  • class 6.1 with a subsidiary risk of class 3;
  • class 8 with a subsidiary risk of class 3, and
  • dangerous goods to which a specific stowage requirement requiring mechanical ventilation in column 16 of the Dangerous Goods List is assigned.
 Stowage Categories for Goods other than Class 1 (Explosives)
Stowage Categories for Goods other than Class 1 (Explosives)

For example, UN 2076 Class 6.1 CRESOLS, LIQUID, stowage category in column 16 of dangerous goods list is Category B. Substances, Materials or Articles assigned with stowage Category B can be loaded on deck or under deck on a cargo ship but on a passenger ship where limiting number of passengers are exceeded Category B must be loaded on deck only!

Segregation between containers carrying dangerous goods are different for containerships with closed cargo holds and hatchless containerships. Vertical and horizontal segregation, athwart ships, fore and aft is defined for Closed Versus Closed, Closed Versus Open and Open Versus Open.

Two closed containers requiring segregation “separated from” each other when loading vertically or horizontally they need to be segregated as shown.
Two closed containers requiring segregation “separated from” each other when loading vertically or horizontally they need to be segregated as shown.

In IMDG Code 37th Amendment Stowage and Handling instructions are listed separately in column 16a in Dangerous Goods List with SW and H codes and column 16b lists out segregation codes, SG.



      1. Hello Lokesh,

        Below are the segregation and stowage sections in IMDG Code
        Chapter 7.1 General stowage provisions;
        Chapter 7.2 General segregation provisions;
        Chapter 7.3 Consigning operations concerning the packing and use of cargo transport units (CTUs) and related provisions;
        Chapter 7.4 Stowage and segregation on containerships;
        Chapter 7.5 Stowage and segregation on roll-on/roll-off ships;
        Chapter 7.6 Stowage and segregation on general cargo ships; and
        Chapter 7.7 Shipborne barges on barge-carrying ships.


  1. Good day, Im trying to find legislation regarding the opening of containers containing 1.4s goods. Please inform me of the designated authorities that must be present when these containers are to be opened at the harbour.
    Many Thanks

    1. Hi Mervin,
      I am not aware which country’s regulations you are asking about.
      Each country, with respect to their local rules, may have designated department responsible for granting permission as well to overseeing the operations of loading/discharging explosives from road vehicles or ships.


    1. Hello Kingsley,

      Classes 3 and 5.1 cannot be together
      Classes 5.1 and 8 cannot be together
      Classes 5.1 and 6.1 cannot be together
      and individual UN Numbers may also have segregation between them which can be checked in column 16b of dangerous goods list in IMDG Code.


  2. hello Shashi
    Please , is cleaning certificate a mandatory document required for an isotank to be loaded on a vessel?

  3. class 1 has 5 stowage categories i.e A to E.
    what about class 2 to 9,,i cant find anything on internet.
    Please guide at the earliest,i have my orals.

    1. Ravneet,

      Closed vs closed means both containers are completely closed containers. Open means a container which is open top or flatrack which is not a completely closed container.
      IMDG Code chapter 1.2 defintions says “Closed cargo transport unit, with the exception of class 1, means a cargo transport unit which totally encloses the contents by permanent structures with complete and rigid surfaces. Cargo transport units with fabric sides or tops are not considered closed cargo transport units; for definition of closed cargo transport unit for class 1, see 7.1.2.”

      “Open cargo transport unit means a unit which is not a closed cargo transport unit.”

      Trust this clarifies.

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