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Hazardous Cargo Freight and Global Transport

Caution, long but essential read

When you think of dangerous goods & hazardous cargo freight, images of primed explosives or nuclear waste might spring to mind.

However, many of you reading this post will likely have many articles or substances in your own home that when part of a domestic or international supply chain will be considered as being a ‘dangerous goods’.

Given recent events in global transport and supply chains, not least the catastrophic explosion in Tianjin China, cargo shippers, forwarders, shipping lines / airlines / hauliers, warehousemen, cargo handlers and just about everyone else involved in the movement of goods considered dangerous are under increased pressure to ensure that each and every shipment complies with DG regulations.

What exactly are dangerous goods?

Dangerous goods can be defined as materials or items with hazardous properties which if not properly controlled, present a potential hazard to human and animal health and safety, the environment and infrastructure.

Dangerous goods can be solids, liquids or gases. They can be hot or cold, pungent or odourless, transparent or coloured and their hazardous effects can be anything from minimal to fatal. They may be pure chemicals, mixtures of substances, manufactured products or individual articles on their own.

Some hazardous effects of these goods can include acidic / caustic burning of skin tissue, the emission of flammable and/or toxic fumes, some products can be corrosive to metals and other materials, others can be explosive by nature or when exposed to sources of heat. Certain goods can be harmful to the environment if not contained properly and others can react dangerously to water.

The transportation of dangerous goods is regulated in order to prevent as far as possible, accidents involving people or property, damage to the environment, to the means of transport employed or to other goods being transported.  Each mode of transport, (air, sea, road, rail and inland waterway) has its own regulations.


IMDG Code bookIMDG Code
or International Maritime Dangerous Goods Code is accepted as an international guideline for the safe transportation of dangerous goods and hazardous materials by sea. The IMDG Code is intended to protect crew members and to prevent marine pollution by hazardous materials.

The implementation of the Code is mandatory in conjunction with the obligations of the members of United Nations Government under the International Convention for the Safety of Life at Sea (SOLAS) and the International Convention for the Prevention of Pollution from Ships (MARPOL 73/78) The code contains advice on terminology, packaging, labelling, placarding, markings, stowage, segregation, handling, and emergency response in relation to carrying dangerous goods by sea.

The 2014 Edition of the IMDG code Incorporating Amendment 37-14 became mandatory on 1 January 2016.


TImage for ADR - European Agreement concerning the International Carriage of Dangerous Goods by Roadhe ADR in Europe (European Agreement concerning the International Carriage of Dangerous Goods by Road) governs the carriage of dangerous goods by road in road vehicles. Its auspices have extended beyond Europe as certain CIS nations have adopted its regulations such as Tajikistan, Kazakhstan and Russia.

In the USA, transporting hazardous materials by road is governed by The Code of Federal Regulations 49, and covers the domestic transportation of hazardous materials for all modes of transport to, from, and within the United States. In Australia the Dangerous Goods act of 2008 governs DG movements by road.


The internationally agreed rules for transporting dangerous goods by air are covered by the International Air Transport Association (IATA) International Dangerous Goods Regulations.

Image for IATA DG BookTransporting dangerous goods globally means that these regulations must be in some way harmonious with one another, as what’s considered acceptable and in line with regulations in the USA for example must meet similar standards in other jurisdictions.

One way this is achieved is by the application of a universally recognised identification code assigned to individual dangerous articles….


The UN Number and what it identifies.

UN numbers are unique four digit numbers – preceded by the letters ‘UN’ – that identify dangerous goods and hazardous substances. Numbers are assigned by the United Nations Committee of Experts on the Transport of Dangerous Goods and are harmonized across the various international dangerous goods regulations.

For example;

Liquid Chlorine (for use in swimming pools) is listed under the entry no. UN1791 in both The ADR and IMDG codes. If one were to look up this entry in either code they would find that the article is listed under its proper shipping name which is ‘HYPOCHLORITE SOLUTION.’ The proper shipping name is the name / title that best describes the substance the entry refers to. PSNs are not always the names of chemicals or scientific sounding. For example, UN 1057s PSN is ‘Lighters or Lighter Refills’

By referring to the IMDG code or the text of the ADR, we can see from the entry under UN1791 that Liquid Chlorine is a ‘Class 8’ substance and can also be sub divided further into either ‘packing group II or packing group III’

Packing Groups are used to define the degree of danger a substance / article poses, with PG I being the most hazardous dangerous and PG II being less so and PG III being the least dangerous. Note: This is not to be confused with having no danger at all.


What are the hazard classes?

As mentioned above in our example, liquid chlorine / HYPOCHLORITE SOLUTION is assigned to ‘Class 8’. But what is Class 8?

Dangerous goods for transport (be it IMDG / ADR / IATA) are divided into separate 9 classes. Some classes are further subdivided into hazard divisions to allow more specific classification.

The following table identifies all 9 classes of dangerous good and also gives an indication as to the typical hazard associated with that class of substance.

image for hazard classes


Individual Hazard Classes are also assigned their own Hazard Danger Label.

These hazard danger labels can be seen on the actual cargo or on transport units such as road trailers or ISO containers containing dangerous goods.

Image for hazardous classes

Dangerous Goods implications on supply chains.

Now that we know what dangerous goods are, we can consider the implications they have on the supply chain.

The ADR and IMDG code could be considered ‘instruction manuals’ for the movement of dangerous goods in supply chains with respect to the relevant mode of transport. Each regulation will outline the certain criteria to be met with respect the type of goods being shipped.

The ADR and IMDG code will tell us – depending on the quantities being shipped – how the substance should be packed for transport for example in steel, wooden, plastics or cardboard packaging, what hazard labels should be placed on the cargo packing and transport unit (and where). It will identify any ‘special provisions’ pertaining to the goods in question, for example, certain goods may not actually be subject to IMDG provisions if less than a certain quantity or weight is actually shipped, or perhaps the special provisions may preclude the cargo from being carried in a unit that is carrying other dangerous goods. It may stipulate that the cargo must be transported under temperature control. Both codes also lay down provisions for the carriage of dangerous substances in portable tanks, tank containers and bulk containers. ADR will even categorize which road tunnels may/may not be used in a journey when a vehicle is carrying a particular substance.

These rules and regulations affect how dangerous goods move through the supply chain by creating maximum awareness of their existence in a shipment and how said shipment is treated. From the added costs incurred in packing and labelling a shipment, the extra scrutiny and attention transport units incur as regards loading and stowage on vessels, to the extra mandatory training required by drivers, warehousemen, cargo handlers and shore side shipping staff, implications can be far reaching.

The number of various instructions to be followed when carrying dangerous goods that can directly affect the supply chain is exhaustive, but nevertheless there is one for every UN number in the regulations, of which there are currently over 3500!


The dangers of un-declared hazardous cargo in supply chains.

Unfortunately, some unscrupulous (and sometimes ignorant) shippers insist on cutting corners and costs by not properly preparing and declaring shipments of hazardous goods. The investigation into the disaster that was the grounding of the MV Rena in 2011 uncovered almost 20 individual cargo containers containing hazardous cargo that was not declared to the shipping line at the time of sailing.

In much the same way that the actual weight of a laden shipping container is difficult to verify, it’s also difficult to verify its contents without inspecting each and every container booked on board a vessel. This is why it’s crucial that shipment contents are declared and verified before acceptance by shipping line, haulier or airline. Failure to do so could result in some potentially disastrous situations.

Cargo needs to be properly stowed on-board a vessel in accordance to its properties. Sometimes the IMDG code requires that transport units are stowed on deck on a vessel whether in a road trailer on a passenger ferry or in an ISO container on the Marco Polo. Undeclared units stowed below deck when they should be stowed on deck are much more difficult to access and tackle in the case of a fire for example.

Some dangerous goods even preclude transportation on board a ro/ro passenger ferry and stipulate that any sea crossing must be undertaken on a ro/ro freight vessel only.

Loaders and planners must know cargo contents so that mixed loading provisions of the codes can be complied with. For example, when goods of classes 6.2 & 3 form part of an IMDG journey, the code states that the goods must be segregated ‘by a complete compartment or hold.’ The reason for this is to prevent ‘incompatible’ goods being loaded and stowed together. Ships planners must also know where and how to position a transport unit containing dangerous goods, e.g. UN3397 – Category E, must be stowed Clear of living quarters and ‘’separated from acids’’ Stowage provisions also relate to positioning in proximity to foodstuffs, marine pollutants and other solutions and mixtures etc.

Cargo handlers need to be aware of what exactly they are handling. An innocent looking powder leaking from a sack could in fact be a caustic or toxic substance that could be fatal on inhalation. A spill from un-marked drums on exposed skin might not seem dangerous at the time, but on contact with water when washing, the substance could react dangerously and cause serious soft tissue damage.

Finally, there’s the possibility of damage to the transport unit itself. Mercury itself is a metal and asides from being poisonous if ingested etc, it can also be corrosive to other metals, particularly aluminium. There have been various incidences of aircraft being written off following a mercury spill in aircraft cargo holds.


Dangerous Goods Awareness.

Clues to identifying DGs that have slipped through supply chains….

Certain clues are obvious to some individuals but not to everybody. If you’re an individual involved with loading / unloading dangerous goods, then one should be aware of shipments that carry any one or more of the above listed Class Hazard Danger Labels. In the examples below, the shipment on the left can clearly be seen to carry a ‘Class 3 Flammable Liquid’ danger label on the package. Perhaps not so obvious is the ‘Class 8 Corrosive Substances’ label affixed to each individual package within the shipment on the right.
dgpacking1image for DG packing







Other marking and labelling to be aware of:

 LQs – Limited Quantities.

Image for limited quantityLimited Quantities as defined by the regulations for the relevant mode of transport allows for the carriage of certain hazardous substance(s) under relaxed guidelines providing certain conditions are met. The main condition being that quantity thresholds of the substance being shipped are limited. Often shippers falsely believe that complying with LQ quantity provisions means they are exempt from compliance in other areas such as declaring LQs shipments, labelling and placarding of transport units.


Excepted Quantity Mark

Image for expected quantityThis mark will generally be affixed to shipments that fall below the LQ threshold. Excepted Quantity shipments are generally very small in nature and as such benefit from very relaxed rules and guidelines. However, this is still an indication that dangerous goods are present within the shipment and due diligence should still be taken.


Orientation arrows

Image for orientation arrowsOften a prerequisite for shipping dangerous goods in liquid form in combination packages. Orientation arrows are required to be affixed to outer packages containing smaller inner packages such as vials and bottles containing hazardous substances.




Image for OverpackOverpack

The term OVERPACK is designated to packages used as an enclosure by a single shipper to contain one or more packages and to form one handling unit for convenience of handling and stowage.



Image for UN No.UN Number

Each package in a dangerous goods shipment (with the exception of certain Limited and Excepted Quantity shipments) are required to display the UN Number of the hazardous substance in the shipment which must be preceded by the letters ‘UN’


Environmentally Hazardous Substance MarkImage for environmental

Marine pollutants or environmentally hazardous substances are materials that pose a risk to aquatic ecosystems. Marine pollutant is a term mainly used by IMDG code while the term “environmentally hazardous substances” are used by other regulations (ADR and IATA)



Image for asphyxiationDanger of Asphyxiation Label

This label is used to warn cargo handlers / drivers of the potential hazards contained within a package or transport unit in circumstances where substances such as Solid Carbon Dioxide (Dry Ice) or Liquid Argon is used as a coolant in the package or transport unit / container.

The label would usually be marked with the name of the substance with the words “AS COOLANT” or “AS CONDITIONER” eg. UN 1845, CARBON DIOXIDE, SOLID, AS COOLANT.


The UN Packaging Code

Image for UN Packaging CodeShipments of Dangerous Goods (with the exception of Limited Quantities and Excepted Quantities) must be packed in UN approved packaging and conform to certain standards of construction and testing. The packing approval code denotes the type of packaging in question, the type of dangerous goods suitable for use within and manufacturer details among other details. It will be this identification mark on whatever type of packaging used in a shipment that may give an indication as to the packages contents in the absence of other marks / labels.

Other items that lend themselves to identifying undeclared dangerous goods, especially in instances where administrative staff are not privy to visuals of the cargo and (DGNs) dangerous goods notes do not exist, can be found on accompanying paperwork and transport documents.


Safety Data Sheets

Safety data sheets provide useful information on chemicals and other substances, describing the hazards the article presents, and giving information on handling, storage and emergency measures in case of an accident.

If a certain substance has been assigned a UN Number, this number will be present on the Safety Data Sheet and as such must comply with the regulations of whatever mode of transport is being used to ship the goods. Not every substance with a safety data sheet however will be classified as a dangerous or hazardous substance.


Terminology on Transport Documents

It is also possible that DGNs (dangerous goods notes) could innocently go missing or be separated from the rest of the consignments paperwork. Closely examining the CMR / Transport Note, B/L, or Airway Bill should also indicate whether or not the goods in question are hazardous. Personnel should be aware of the description of the goods. Keep an eye out for words and phrases like the UN Number – UN****, Hazard Class Number or Packing Group, Tunnel Code, PSN – proper shipping names. Other phrases such as ‘limited quantities’, ‘excepted quantities’, ‘wastes’, ‘salvage packaging’, ‘empty uncleaned’, ‘empty packaging containing residue’, ’environmentally hazardous substances’, ‘inner packing’, ‘outer packing’, ‘combination pack’, ‘used as coolant’, ‘exempt under…..’.

These are just a few examples.

Also, in the absence of other identifying information, always practice due diligence where the description of the goods being shipped sounds like a chemical substance. For example, Mercury Oxide, Carbonyl Fluoride, Ethylamine. However, this isn’t a failsafe method for identifying dangerous goods on documentation. Plenty of ‘everyday’ substances have been assigned a UN Number and must follow the DG instructions associated with the substance. Nicotine – UN1654, Compressed Air – UN1002, Alcoholic Beverages – UN3065, Matches – UN1944, Flares (numerous entries), First Aid Kits – UN3316.


‘Ordinary’ Dangerous Goods….

As mentioned at the beginning of this post, there are many everyday items that we may even have in our homes that fall under the auspices of International Regulations for the Carriage of Dangerous Goods when part of supply chains.

The following is a small example of some of those items so that shippers, cargo handlers and administrative staff might be more aware of the sensitive nature of certain cargoes that they’re handling.

  1. Batteries,
  2. paints,
  3. solvents and paint thinners,
  4. aerosols, perfumes, some deodorants,
  5. gases in the form of pressurised cylinders like portable camping stoves,
  6. compressed air canisters like oxygen tanks,
  7. corrosive substances like caustic soda and bleaches, dry ice for use as a coolant,
  8. firelighters, matches, cigarette lighters,
  9. air bag units for vehicles, emergency flares, self-inflating life jackets and rafts,
  10. certain magnetised materials,
  11. cell phones and other devices with chargeable lithium batteries,
  12. fire extinguishers,
  13. pesticides, insecticides,
  14. fertilizers,
  15. dry cleaning solvents,
  16. de-icer,
  17. glass cleaner,
  18. adhesives, glues………………

About the Author

David MuckianDavid Muckian is a director of a small independent freight forwarder based in Dublin..

David has been in the freight and transport industry for the past 10 years and hold numerous diplomas pertaining to the industry such as ‘International Transport Management for Road Freight Operations’, the ‘FIATA Diploma in Freight Forwarding’, ‘Diploma in International Trade and Finance’ (Institute of Export UK) along with vocational qualifications in ‘Customs Regulations and Dangerous Goods..

David is also a qualified Dangerous Goods Safety Advisor for both road (ADR) and sea (IMDG) shipments..

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  1. If cargo is hazardous under DOT classification but is not hazardous under IMDG classification; how would a shipper send the shipment by truck to a dock that has to be loaded on a boat then shipped offshore to an offshore facility? This creates a gray area in the aspect that if the truck were pulled over by DOT and wasn’t marked or manifested as hazardous they would be in violation of DOT Regs. So what happens if the truck does mark the cargo and manifest the cargo as hazardous cargo but now it’s deemed not hazardous under IMDG when shipping by sea? Does the IMDG Regs statement of this same cargo being considered non-hazardous now impose a violation of shipping hazardous cargo that is not considered hazardous cargo? This puzzles me… In addition if a hazardous cargo has an RQ (reportable quantity) and you don’t meet that reportable quantity is it still considered hazardous cargo or do you not have to report the quantity?

    Kindest Regards,
    Andy Luther

  2. I have couple of question on the Placarding of CTU, hope you are able to assist me to understand the requirements.

    1. Is UN number required for each product within the CTU with a gross weight exceeding 4000kg.”

    IMDG Code Section states: “packaged dangerous goods loaded in excess of 4000 kg gross mass, to which only one UN number has been assigned and which are the only dangerous goods in the cargo transport unit.” (see attached extract from IMDG 38-16).
    Going by what the IMDG Code states, does it mean that if more than one DG product, with each of the products having a gross mass greater than 4000kg, then you don’t have to display each of the UN Numbers on the FCL. If you have only one DG product in an FCL and it has a gross mass greater than 4,000kg, then the UN Number is required. Also, Section which states that you can place the UN Number in 120mm letters on the DG placard, however, if you had multiple products in a FCL of the same DG Class, there is insufficient room to add more than one UN Number on the placard so that they do not “…obscure or detract from the other required placard elements…” and only one placard for each DG Class, or Subsidiary Risk, is required on each side of an FCL.

    2. Is IMO Class and Subsidiary Risk required for each class of DG…..”,

    Under IMDG Code Section it states “…..cargo transport units containing goods of more than one class need not bear a subsidiary risk placard if the hazard represented by that placard is already indicated by a primary risk placard.”, ie., in an mixed FCL you have products with different UN Classes and one product has a Subsidiary Risk Class which is the primary risk Class of another product in the FCL, then you do not have to have the Subsidiary Risk placard for the first product.

    Summarising the above requirements, is it correct to say:
    1. Where multiple products of different DG Classes, each of gross greater than 4,000kg, are shipped in the same FCL, that the UN Numbers of each product do not have to be displayed. Only the placard for each DG Class within the FCL is required.
    2. Where multiple products of the same DG Class are shipped in the same FCL, the UN Numbers of the products do not have to be displayed, irrespective of whether or not the gross of any of the products is greater than 4,000kg.
    3. Where mixed FCLs of an FCL has product/s which have a Subsidiary Risk which is the same as the primary risk of another product within the same FCL, Subsidiary Risk placards are not required.

    Appreciate you help.

    Thank you.

    • Hi Thejo, David has responded as below.. Trust this helps..


      The first question is quite interesting, and your reader will be interested to know that this has been asked publicly before.

      The IMDG code, whilst having been revised to make this provision clearer, has not really gone far enough to ensure clarity. This link dated 2001 ought to answer this very question.

      The keyword that your reader must take into consideration in respect of this provision is the word only.


      “ packed dangerous goods loaded in excess of 4000kg gross mass to which ONLY one UN number has been assigned and which are the only dangerous goods in the transport unit……”

      So, a transport unit with more than one type of DG greater than 4000kg etc, is precluded from this provision.

      In question 2, your reader has effectively answered his own question. He is correct in interpreting the rules to mean that a sub risk placard is not required, on the provision that there exists a primary risk placard for another substance on board,

      For example.

      The concentrate product from which a lot of Coca Cola products is made, is manufactured in a factory in a little town on the west cost of Ireland called, Ballina, and then exported all over the world!

      This concentrate is considered a dangerous good and is a class three flammable liquid with a sub risk of class 8 corrosive properties. ( sounds healthy, right! )

      If mixed loading rules allows for it, and a different product of class 8 corrosive product can also be loaded on board the CTU, then the primary placard for the class 8 corrosive substance sufficiently covers the requirements for the sub risk placard for the concentrate product.


  3. Great article with a lot of detail which can be updated with the revised GHS symbols now in use. The whole question of cargo compatibility and formulated products is such a big subject with plenty of guidance literature available that I hope your readers explore themselves. Glad that the IMDG work is being more widely accepted.


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