How To Ship Dangerous Goods by Sea

How to ship DG Cargo

One short article will not come close to cover the vast topics to comprehend the ins-and-outs of transporting dangerous goods.

With this article we will try to explain the process of transporting dangerous goods, here is how we are going to do it.

  • Introduce the International Maritime Organization (IMO)
  • Describe the 9 classes of dangerous goods and it’s divisions
  • Use real cargo examples to explain the key area to focus on


More often than not, the owners of the cargo know more about the dangerous goods than the transporter, good communication between exporters and importers is essential to safely transport goods that are dangerous in nature.

50 percent of cargoes transported by sea is dangerous in nature, for example, wood in its natural state is considered non-dangerous goods, but introduce it to fire and it’s flammable nature comes to fore.

Which is why we need a code of conducts, conventions and governing bodies to regulate the transportation of goods in order to keep safe from pollution or death of lives.

The International Maritime Organization (IMO) serves that sole purpose.


Many things happened in 1948, the inauguration of the General Agreement on Tariff and Trade (GATT), the assassination of Mathama Gandhi and the establishment of the World Health Organization (WHO) to name a few.

the International Maritime Organization (IMO) is established as the first international body solely devoted to maritime matters only, it is a significant event that shaped the way maritime transportation is conducted.

Since then, it has promoted 50 conventions and protocols and 1000 codes and recommendation concerning maritime safety and pollution prevention.


The IMO promptly erected the International Maritime Dangerous Goods Code (IMDG Code) and has since been accepted widely as an industry practice for safe transportation of dangerous goods by any mode of transportation.

Every two years a revised IMDG Code is issued by IMO to keep up the current times. If you are a regular in transporting or trading different chemicals, we suggest investing in purchasing the IMDG book.

At the end of the day, the objective of the IMDG Code is to ensure the safety of lives at sea and also prevent environmental pollution.


DG Class 1 comprises of explosive substances, whether it is a in a solid, liquid or gas state

Gas, vapour or dust emitted by a substance is not categorized in class 1

DG class 1 has 6 divisions, as we go from 1.1 to 1.6 the level of threat generally decreases with 1.1 the most dangerous to 1.6 the least dangerous

DG Class 1Class 1:
Comprises of explosive substances, whether it is in a solid, liquid or gas state
DG-Class-1.1Division 1.1
Substances and articles which have a mass explosion hazard.
DG Class 1.2Division 1.2
Substances and articles which have a projection hazard but not a mass explosion hazard
DG Class 1.3Division 1.3
Substances and articles which have a fire hazard and either a minor blast hazard or a minor projection hazard or both, but not a mass explosion hazard
DG Class 1.4Division 1.4
Substances and articles which present no significant hazard
DG Class 1.5Division 1.5
Very insensitive substances which have a mass explosion hazard
DG Class 1.6Division 1.6
Extremely insensitive articles which do not have a mass explosion hazard


Gas is a substance which, at 50°C has a vapor pressure greater than 300 kPa; or is completely gaseous at 20°C at a standard pressure of 101.3 kPa.

Gas can be in a state of liquefied or compressed.

According to their chemical properties or physiological effects, which may vary widely, gases may be: flammable; non-flammable; non-toxic; toxic; supporters of combustion; corrosive; or may possess two or more of these properties simultaneously.

Different chemical compound also have different placard that is specific to the hazard it carries. These labels and placards are the more commonly seen.

For further information, we stress that you should look at the IMDG Code book, it is updated once every 2 months, and you have to keep yourself updated.

Class 2:
Gasses, in its many states, that are dangerous in nature
DG Class 2.1Division 2.1
Flammable Gas
DG Class 2.2Division 2.2
Non Flammable Gas
DG Class 2.3Division 2.3
Toxis Gas


Dangerous Goods Class 3 consists of Flammable Liquids with a varying boiling point having different packing criteria.

DG Class 3Class 3:
Flammable Liquids


DG Class 4 are Flammable solids; Substances liable to spontaneous combustion; Substances which, in contact with water, emit flammable gases.

Class 4:
Flammable Solids
DG Class 4.1Division 4.1
Flammable solids. Solids which are readily combustible or
may cause or contribute to fire
DG Class 4.2Division 4.2
Substances which are liable to spontaneous combustion.
DG Class 4.3Division 4.3
Substances which, in contact with water, emit flammable gases.


DG Class 5 consists of oxidizing substances and organic peroxides.

Class 5:
oxidizing substances and organic peroxides.
Division 5.1
Oxidizing substances are substances that yields oxygen which can be
combustible in certain conditions
DG Class 5.2Division 5.2
Organic Peroxide may be considered a derivative of hydrogen peroxide, that has
organic radicals. They are thermally unstable


DG Class 6 consists of toxic and infectious substances

Class 6:
Toxic and Infections Substances
DG Class 6.1Division 6.1
These are substances liable either to cause death or serious
injury or to harm human health if swallowed or inhaled, or by skin contact.
DG Class 6.2Division 6.2
These are substances known or reasonably expected to contain pathogens.
Bio-hazardous materials which are infectious


Dangerous Goods Class 7 consists of Radioactive Materials

Class 7:
Radioactive substances comprise substances that emit ionizing radiation.


DG Class 8 consists of substances which, by chemical action, will cause severe damage when in contact with living tissue or, in the case of leakage, will materially damage, or even destroy, other goods or the means of transport.

DG Class 8Class 8:
Corrosive Material, capable of corroding live tissue or metal.


DG Class 9 consists of substances and articles (miscellaneous dangerous substances and articles) are substances and articles which, during transport, present a danger not covered by other classes.

DG Class 9Class 9:
Hazardous substances that do not fall into the other categories


The best way to explain the requirements of Dangerous Goods transportation is by giving an example

The information below are typically found when you search for the UN Number of a particular cargo, which can be pinpointed from the Material Safety Data Sheet.

Once you are able to find the proper UN Number for your cargo, it is just a matter of adhering to the conditions set by the IMDG Code book.

case study DG cargo
Case study DG Class 3


UN Number, assigned by the United Nations Committee of Experts on the Transportation of Goods, directly categorize the Dangerous Goods Class of the cargo.

For this case the UN Number of 1235 classifies the cargo as –

DG Class 3 – Goods Flammable Liquid with a subsidiary;
DG Class 8 – Goods Corrosive Substance


The standardized technical term for the underlying chemical/cargo. For example, Methylamine can also be called Aminomethane Monomenthylamine.

Additional, a chemical compound can be derived from other chemicals too, but the underlying characteristic of the chemical reflects that of Methylamine.

Since the cargo will exchange hands between multiple parties at multiple locations, it is better to standardize the shipping name so everyone knows for sure what the cargo is.

Alternatively, should you encounter a situation where you do not know the UN Number of the cargo, and a Proper Shipping Name is not determined?

You can refer to the Chemical Abstracts Service (CAS Number) which is available in the Material Safety Data Sheet and pair it to the UN Number


This is used as a mean to categorize the type of dangerous goods and it’s inherently dangerous properties. UN Number 1235 has a DG Class of 3 – Goods Flammable Liquids


This is used as a mean to categorize the type of dangerous goods and it’s inherent secondary dangerous properties. UN Number 1235 has a subsidiary

DG Class of 8 – Goods Corrosive Substance


There are 3 Packing Group any individual UN Number is properly categorized by the IMO IMDG Code book.

Packing Group I: High Danger, maximum segregation, and most protective packaging required
Packing Group II: Medium Danger
Packing Group III: Low Danger

What happen if there is a mixture of hazardous material?

Whenever there is a mixture of hazardous materials, we need to determine the packing group by first referring to the Precedence of Hazardous Table. The purpose is to determine the primary hazard class among the 2 mixed materials.

As a pure example, does not mean it is physically possible in a real scenario, UN Number 1235
(Methylamine) is physically mixed with UN Number 2295 (Menthyl Chloroacetate):-

UN Num PSN DG Class Description Packing Group
1235 Menthylamine 3 Goods Flammable Liquid II
1755 Chromic Acid Solution 8 Miscellaneous Dangerous Substances and Article III

Which Packing Group are we suppose to refer to?

Precedence of Hazard table
In this instance the Precedence of Hazardous Table is used below, the Packing Group to refer to is Packing Group II


For this example there are no special provision allocated for this chemical cargo.

Special provisions cover specific requirements for the relevant UN Number, it can come in form of packing method, the content of the chemical cargo, additional test requirements, and much more additional information pertaining to the cargo.


Limited Quantity indicates the maximum quantity per packaging.

For Menthylamine I L generally indicates that in one package the maximum packaging is up to One Liter.


Menthylamine has an excepted quantity of E2, referring to the graph below,

Code Maximum net quantity per inner packaging
(in grams for solids and ml
for liquids and gases)
Maximum net quantity per outer packaging
(in grams for solids and ml for liquids
and gases, or sum of grams and ml
in the case of mixed packaging)
E0 Not permitted as excepted quantity
E1 30 1000
E2 30 500
E3 30 300
E4 1 500
E5 1 300

Hazardous goods are always packed in the inner package and outer package. During transit, the cargo is subjected to forces that will unstabilize the goods.

The IMDG Code has specific requirements for the outer and inner packaging load capacity in order to keep it within the safe zone.


P001 – refers to the specifications of the packaging unit used for UN 1235 transportation. It details the specification for inner packaging materials, outer packaging material and the maximum capacity depending on the packing group mentioned above.

Packing Group I has the highest transport risk therefore the maximum capacity for packing group I is only 75kg. Packing Group III is low danger hence the maximum capacity is 400kgs.


IBC refers to Intermediate Bulk Containers, a form of reusable, industry grade container that comes in many shapes and forms. Primarily it is used for carrying hazardous materials.

Due to its wide use to transport hazardous material, and it’s wide ranging shapes and forms, the IMDG Code has special provisions and conditions for exporters to use as a guideline to transport goods.

In this instance, UN 1235 has an IBC02 instruction, which authorizes the use of metal, rigid plastic and composite containers to store it.


Tank Instruction refers to an alphanumeric design from (T1 to T75). It indicates the applicable conditions to transport dangerous goods in a portable tank.

In this instance, according to the IMDG Code, T7 allows the minimum test pressure (bar) of 4 and generally indicates the minimum steel shell thickness allowed to transport the UN Number 1235 Goods


This provides the response protocol in the event of an emergency like fire and spillage happens during transportation.

UN 1235’s F-E schedule indicates to the transporter:-

  1. How to approach the cargo on fire,
  2. How to put out the fire if cargo is on-deck or off-deck,
  3. How does the dangerous good react to water or other chemicals

UN 1235’s S-C spillage schedule indicates that liquid cargo is both flammable and corrosive, it teaches us:-

  1. How to handle spillage whether on-deck or off-deck,
  2. What other chemicals will react with it
  3. the general comments about what to expect from cargo spillage and how to prepare for it
  4. Who to report to in the event of spillage


UN DG Code also outlines the what dangerous cargo can be shipped together, what dangerous cargo cannot be staged at the same area.

With this cargo, the UN DG Code also detailed which Dangerous Goods Group in which this cargo has to be segregated.

Crucially, the segregation schedule gives the importer and exporters a firm reference to how NOT to ship multiple chemicals together so that no dangerous event that may occur will cause damage to the freight ship, the environment and most importantly endangering human lives.


Each package has to be labeled with the proper DG labels that correspond to UN Number 1235 which are the Class 3 and Class 8 labels with a minimum dimension of 100mm by 100mm in size

CTUs also has to be labeled with the Class 3 and Class 8 Placards prominently with a minimum dimension of 250mm x 250mm

Minimum Dimensions for Labels: 100mm by 100mm
Minimum Dimensions for CTU Placards : 250mm by 250mm


Proper care and caution has to be exercised whenever you transport dangerous goods by sea and air, and also to make sure that you have the proper marine cargo insurance covered and also be wary of the ocean freight rate fluctuations.



Hello! I'm Kelvin, I work as a custom broker and I'm thrilled with having the experience to share my industry knowledge with you. I hope that you enjoy reading them as much as I do posting them.

One thought on “How To Ship Dangerous Goods by Sea

  1. Hi Kelvin,

    I am a Business manager at J&K Scientific, a reagent distribution company.
    I am exploring the possibility of shipping by sea class 4.2 products
    Trichlorosilane, 98% (1 L)
    Lithium dimethylamide, 10% w/v in hexane
    from China to Singapore.

    Is this possible? What steps should I take?


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