All About Dangerous Goods (IMO Cargo): SeaRates Guide

There is one category of goods that invariably draws higher revenue in the service of ports, carriers, and insurance companies in international trade. These are dangerous goods or IMO cargo consisting of goods that may pose a risk to human life, a ship, or the environment.

And with the adage "dangerous," most of these cargoes are, in fact, perfectly safe, doing things by the book laid down by the IMDG Code (International Maritime Dangerous Goods Code). Trouble arises when the exporter is either unaware or negligent of the finer details. 

This article is a neat guide for shippers, carriers, and freight forwarders working with or planning to ship IMO cargo. It examines what falls within the terminology of "dangerous" cargo, including which classes are most commonly "stuck" in ports, the documents a container must have to gain acceptance on a ship, and how to avoid the most common mistakes.

9 classes of dangerous goods

Note: Each class has its own packaging, marking, and placard instructions (markings on the container). If these markings are absent or wrong, as well as packing or loading, the container cannot be admitted into the port or onto the ship. So, pay attention to labeling and proper container loading to ensure efficient and secure delivery and unloading further.

Which cargo classes most often get “stuck” in ports?

Cargo delays in ports are generally not attributable to the "dangerous" nature of the cargo itself, but rather to human factors along with documentation issues, mostly. Here are some common scenarios:

Class 3 — Flammable liquids

Paints, varnishes, solvents, perfumes, disinfectants.

Most often detained and delayed for wrong or no declaration or absence of MSDS (material safety data sheet).

Typical situation: the exporter simply states “paint” instead of “Paint, flammable, UN1263, Class 3, PG II”.

You planned your route and made your reservations according to the shipping schedule to minimize the risk of losing your space while correcting your documents. However, the shipping line may block the container and require a DGD (dangerous goods declaration) correction, resulting in the loss of your shipment.

Class 5 — Oxidizers and organic peroxides

Chemical reagents, fertilizers, disinfectants.

Problems — incompatibility with other cargoes.

Example: a loader placed a Class 5 container next to a Class 3 container (flammable liquids). The port authority blocks the shipment right away for fear of a mutual reaction. The container has to be segregated, which may last for days.

Class 8 — Corrosive substances

Acids, alkalis, electrolytes.

Concerns are damage to the packaging. Even a small leak = automatic ban on loading.

Example: There was a slight acid stain on a pallet; the port service requires disposal of the packaging or repacking of the goods. Delay: 5 days maximum, plus additional cleaning charges.

Class 9 — Other dangerous substances (especially lithium batteries)

The most common “stuck” class in 2020–2025.

The problem is the inconsistency of documents and labeling.

Example: The company ships electric scooters with built-in lithium-ion batteries, but fails to state that the batteries are Class 9. While scanning, the port finds the batteries, and the container is blocked and blacklisted by the carrier.

After dispatch, keep track of the shipment status via SeaRates Container Tracking, as it helps you react quickly if the container is “stuck”.

Why are ports particularly vigilant?

After a number of major accidents, namely in Beirut, Tianjin, and Hamburg, seaports have been enforcing extreme controls.

The container may be:

• unpacked for inspection;

• sent to a special site for verification;

• disposed of without compensation (if the risk is high).

Thus, a small mistake in the UN number or an incorrect label can cause loss of thousands of dollars and a contract.

Documentation: essentials for the container to be accepted

Dangerous cargo is always subject to the rules of shipping documentation. For containers to be allowed for shipment, a complete set of IMO documentation must be submitted, with each document adhering to the IMDG standards.

1. Dangerous Goods Declaration (DGD)

This is the main document from the sender, which specifies:

• Proper Shipping Name (official name of the substance),

• UN Number,

• Class, Subclass, Packing Group,

• quantity, type of container, temperature, density,

• confirmation that the packaging complies with IMDG requirements.

The exporter or authorized representative signs the DGD. The container cannot gain entry into the port without this transportation document.

2. Material Safety Data Sheet (MSDS)

A safety data sheet from the manufacturer of the goods. It tells of the physical and chemical properties; hazards; safe handling measures; spill response, clean-up, etc. The carrier uses the MSDS to check whether the cargo does indeed fit its stated class.

3. Container Packing Certificate (CPC)

Proof that cargo has been loaded and packed correctly, free from damage or leakage; separation of incompatible substances has been taken care of. The CPC is usually signed by the forwarder or packing company.

4. Transport Document / Bill of Lading (B/L)

The field for the description should note that the cargo is an IMO cargo:

UN 3480, Lithium-ion batteries, Class 9, PG II, Marine pollutant

or a similar format for your product.

5. Packaging certificates (UN packaging certificate)

Every packaging for IMO cargo shall be capable of being certified under UN standards. The marking on the packaging shall be:

4G/Y30/S/23/UA/123456

where “UA” is the country that certified the packaging.

6. Container marking

Each side of the container will bear placards (stickers with the class symbol) and inscriptions with the correct Shipping Name. The stickers should be waterproof, with a minimum size of 250 mm, and in a contrasting color.

You can conveniently set rates and make bookings in the Logistics Explorer tool. For non-standard routes or digital support needs for your logistics, please submit your query via Request an IT Quote.

How does it work in practice?

If there is any document missing or if the details conflict (for example, a discrepancy between DGD and B/L), the container will not be allowed to be loaded.

Furthermore, the big carriers (Maersk, MSC, and CMA CGM) take the extra step to automatically boycott such a container inside their computer systems, where even a line manager cannot "push" it through without the updated documentation.

Common mistakes and how to avoid them

Even the very professional ones sometimes fall into the simplest former errors. Here is a list of the most common ones — compare it with your case:

1. “Hidden” dangerous cargo

Goods are declared as ordinary when they, in fact, fall under IMO.

Example: “cleaning agent” or “solvent” without specifying the class.

This means that the container is stopped, and a fine of up to $10,000 is imposed, plus a six-month ban on shipments.

2. Incorrect packaging

Plastic canisters are not used in accordance with UN certification, nor pallets meeting IMO requirements. On inspection, the port would ask for repackaging, which means missing the flight.

3. Discrepancies in documents

The UN Number on the DGD does not correspond to what is on the MSDS or B/L. The names must match absolutely, even the order of words.

4. No prior agreement with the line

Every shipping company has its own list of cargoes approved for IMO. If you do not get pre-approval, the container may not even be accepted with perfect documents.

5. Insufficient container labeling

Placards that are only affixed on two sides or are damaged are grounds for automatic “stopping” for further clarification.

Checklist “How to avoid delays and fines”

To avoid worries in coordinating the movement of your container with dangerous goods, work your way through this checklist:

✅ 1. Check the UN Number and classification

Check your goods against the IMDG Code or UN database before booking a container. This can be done online — the IMO has an open database.

✅ 2. Agree on the IMO cargo with the shipping line

Request pre-approval with the following data:

• MSDS,

• DGD (draft),

• cargo and route description.

You will accept the offer by declaring your agreement, and then you will be able to make a reservation without any risk.

✅ 3. Use certified packaging

Work only with vendors supplying containers conforming to the UN certification standards. All containers or boxes have to bear UN markings.

✅ 4. Check the markings

Ensure that IMO classification labels are affixed to the container on all four sides, are in a good state of visibility, and correspond to the class stipulated in the DGD.

✅ 5. Prepare a complete set of documents

• DGD (Dangerous Goods Declaration)

• MSDS

• CPC (Packing Certificate)

• Bill of Lading (with IMO mark)

• UN packaging certificates

• Insurance policy (recommended)

✅ 6. Coordinate with the forwarder and port

Give a prior notification to the port service that the cargo is IMO comprising. In most cases, the terminals arrange for a separate storage area, and in the absence of such an intimation, they will simply refuse to allow entry of the container.

✅ 7. Train your staff

All persons involved in packing or completion of paperwork should be IMO trained (at least should possess the Foundation Course in IMDG Code); it is a certification that at least 50 per cent of the staff should have, and more practically, all, if not all, of them.

Discover cases

At SeaRates, we see hundreds of cases every week when your cargo could potentially be delayed due to very minor errors. Let's look at a few examples of mistakes that are easy to fix.

Case 1. Paint and varnish products, Class 3

The exporter declared "paint materials" without indicating the class as Class 3.

MSC instituted a hold on the container before loading.

In result, there are delay for ten days, repackaging was necessary, and a fine of $2,500.

Lesson: check each time the UN Number (UN1263) and the full name with classification must be indicated.

Case 2. Fertilizers, Class 5.1

A container with nitrates was put next to food products.

The port detected a segregation violation during the inspection.

Cargo had to be relocated at a further cost of $1,200 and a lost slot. 

Lesson: Check the compatibility of the class before loading it into a container or anywhere nearby.

Case 3. Electric scooters with lithium-ion batteries, Class 9

The exporter did not state that batteries were in the package.

Maersk blocked the booking, after which the company received an official warning.

Lesson: Lithium batteries require UN 3480 or 3481 special markings and a separate declaration.

Why proper preparation is beneficial, not bureaucratic

Many exporters see IMO requirements as "unnecessary paperwork." In reality, however, they are your insurance against downtime, fines, and customer losses. If cargo is well packed, it will pass the port inspection on the first attempt, be expedited in loading, and after that generate positive reviews by the shippers and insurer.

If the documents are incorrect or the label is done "as is," a week's delay and tens of thousands of dollars in losses could be incurred, even for a very short voyage.

Conclusion

IMO cargoes are not just “chemicals” or “hazardous substances". They are a major part of modern trade-from cosmetic preparations to batteries for electronics. And the sooner you, as an exporter or freight forwarder, learn the complexities of working with the supply chain, the more predictable it will be for you.

Dangerous cargo is not the problem, but rather the cargo that needs special attention. As long as you abide by the rules, have proper documentation, and have the cooperation of the carrier, your IMO container should never “get stuck” at the port.

If you want to move cargo fast and save money, irrespective of IMO class, contact us at [email protected] for a personalized logistics solution for your business.