IMDG Code in Shipping: Dangerous Goods Classes, Declaration, Stowage, and Charterparty Duties

The International Maritime Dangerous Goods Code (IMDG Code) is the principal international framework for the safe carriage of dangerous goods by sea in packaged form. The IMDG Code is maintained by the International Maritime Organization (IMO) and is used by shipowners, charterers, ship masters, shippers, freight forwarders, port authorities, terminal operators, and container operators to identify dangerous goods, classify hazards, apply correct packing and marking standards, and determine safe stowage and segregation on board a ship.

In practical shipping terms, the IMDG Code helps ensure that dangerous goods are described accurately, packed safely, marked and labelled correctly, documented properly, and stowed in a position that does not endanger the ship, crew, cargo, port personnel, or marine environment. The IMDG Code is especially important in container shipping, breakbulk cargo operations, and any trade where hazardous materials may be carried in packaged form. In dry bulk shipping, related safety duties may also arise under the IMSBC Code when dangerous solid bulk cargoes are carried without packaging.

For chartering and ship operations, the IMDG Code is not merely a technical reference. It affects cargo acceptance, charterparty clauses, ship suitability, freight negotiations, stowage planning, port approvals, cargo documentation, insurance, liability, delay risk, and the ship master’s right to refuse unsafe or improperly declared cargo. A dangerous cargo mistake can lead to fire, explosion, toxic exposure, pollution, port detention, cargo rejection, demurrage disputes, loss of insurance protection, or serious casualty.

What is the IMDG Code?

The IMDG Code is an internationally recognized code for the maritime transport of dangerous goods and marine pollutants. It provides detailed requirements for the safe shipment of hazardous materials by sea, including the classification of dangerous goods, UN numbers, packing groups, packaging standards, marking, labelling, placarding, documentation, stowage, segregation, and emergency response guidance.

The IMDG Code was developed to create a uniform system for dangerous goods shipped internationally. Without such a common system, ship operators and port authorities in different countries would face inconsistent descriptions, labels, packing practices, and safety procedures. The IMDG Code reduces that uncertainty by providing a shared language for dangerous goods carriage.

The IMDG Code is closely connected with SOLAS and MARPOL. Its purpose is to protect life at sea, prevent accidents on board ships, reduce the risk of marine pollution, and support the safe flow of international trade. Although the IMDG Code began as guidance, its key provisions became mandatory under SOLAS for the international carriage of dangerous goods by sea.

Dangerous Goods and Hazardous Materials at Sea

Dangerous goods are substances, materials, or articles that may present a risk to people, property, ships, cargo, or the marine environment during transport. These risks may arise from explosion, fire, toxicity, radioactivity, corrosive action, oxidizing properties, spontaneous combustion, dangerous reaction with water, or environmental harm.

Dangerous goods can include industrial chemicals, paints, solvents, acids, batteries, gases, pesticides, fertilizers, radioactive materials, oxidizing agents, explosives, aerosols, flammable liquids, self-heating products, and environmentally hazardous substances. Some cargoes are obviously dangerous, while others may appear harmless unless their chemical properties, moisture content, temperature sensitivity, or reaction risks are understood.

For this reason, proper cargo identification is the first step in safe dangerous goods carriage. A shipowner or ship master cannot safely assess the cargo if the shipper has provided an incomplete, misleading, or incorrect description. Misdeclaration is one of the most serious risks in dangerous goods shipping because it may cause incompatible cargoes to be stowed together, emergency responders to receive wrong information, or the crew to be unaware of the real danger on board.

The 9 Classes of Dangerous Goods under the IMDG Code

The IMDG Code organizes dangerous goods into nine internationally recognized hazard classes. These classes are used in documentation, labels, placards, emergency response planning, and stowage decisions.

Class 1: Explosives – substances and articles capable of explosion, mass explosion, projection hazard, fire hazard, or other explosive effects.
Class 2: Gases – compressed, liquefied, refrigerated, dissolved, flammable, non-flammable, non-toxic, or toxic gases.
Class 3: Flammable Liquids – liquids that give off flammable vapours and may ignite under transport conditions.
Class 4: Flammable Solids and Related Substances – flammable solids, self-reactive substances, substances liable to spontaneous combustion, and substances that emit flammable gases when in contact with water.
Class 5: Oxidizing Substances and Organic Peroxides – cargoes that may cause or intensify fire, release oxygen, or decompose dangerously.
Class 6: Toxic and Infectious Substances – substances that may cause death, injury, illness, or infection through inhalation, ingestion, or skin contact.
Class 7: Radioactive Material – materials containing radionuclides above defined activity limits.
Class 8: Corrosive Substances – substances that can destroy living tissue or damage other cargo, packaging, equipment, or ship structure.
Class 9: Miscellaneous Dangerous Goods – dangerous substances and articles that do not fall neatly into the other classes but still present a transport risk, including marine pollutants and certain lithium battery cargoes.

What Information Does the IMDG Code Provide?

The IMDG Code provides practical transport instructions for each regulated dangerous good. This information allows the shipper, carrier, port, terminal, and ship master to understand how the cargo must be prepared and handled before it is loaded on board a ship.

The IMDG Code commonly addresses:

Proper Shipping Name and technical cargo description.
UN Number used to identify the dangerous good internationally.
Hazard Class and Division for the type of danger presented.
Packing Group where applicable, indicating the degree of danger.
Packing Instructions and permitted packaging types.
Marking, Labelling, and Placarding requirements.
Dangerous Goods Declaration and transport documentation.
Stowage Category and permitted stowage location.
Segregation Requirements for incompatible cargoes.
Marine Pollutant identification where relevant.
Emergency Response and medical first aid guidance through IMDG Code supplementary materials.

IMDG Code and Ship Chartering

In ship chartering, the IMDG Code becomes a commercial and contractual issue as well as a safety issue. A charterer may wish to load cargo that is classified as dangerous goods. Before accepting that cargo, the shipowner must confirm whether the ship is suitable, whether the cargo is permitted under the charterparty, whether the cargo can be stowed safely, and whether all documentation has been provided correctly.

Many charterparties include cargo exclusion clauses or dangerous goods clauses. These clauses may prohibit certain dangerous cargoes entirely, restrict their quantity, require prior written approval from the shipowner, or oblige charterers to provide complete IMDG Code documentation before shipment. In time charterparties, this is particularly important because charterers normally have wide employment rights, but those rights do not entitle charterers to expose the ship to unlawful, unsafe, or misdeclared cargo.

A shipowner may also reserve the right to reject, discharge, land, destroy, neutralize, or make harmless any dangerous goods that were shipped without proper notice or contrary to the contract and applicable law. Under the Hague and Hague-Visby Rules, dangerous cargo provisions may impose serious consequences on shippers who load dangerous goods without the carrier’s informed consent.

Charterparty Clauses for Dangerous Goods

Dangerous goods clauses should be drafted clearly. A general permission to carry lawful merchandise may not be sufficient where a cargo requires special ship equipment, special crew training, temperature control, segregation, ventilation, fire protection, or port permission. A properly drafted clause should state whether dangerous goods are allowed, which cargoes are excluded, what documents must be provided, and what rights the shipowner has if the cargo is unsafe or misdeclared.

Key points to consider in charterparty drafting include:

Prior Approval: whether dangerous goods require the shipowner’s written approval before shipment.
Cargo Description: whether charterers must provide full Proper Shipping Name, UN Number, class, packing group, quantity, and packaging details.
Compliance Warranty: whether charterers warrant compliance with the IMDG Code, port rules, flag requirements, and applicable law.
Stowage Responsibility: whether charterers or shipowners are responsible for stowage and segregation.
Indemnity: whether charterers indemnify shipowners for loss, delay, fines, claims, and expenses caused by dangerous cargo non-compliance.
Right to Refuse Cargo: whether the ship master may refuse unsafe, wrongly declared, leaking, damaged, or improperly packed dangerous goods.
Emergency Rights: whether the shipowner may discharge, destroy, or render harmless dangerous goods that threaten the ship or other cargo.

Dangerous Goods Declaration in Shipping

The Dangerous Goods Declaration is a central document in dangerous goods transport. It is a formal declaration by the shipper confirming the nature, identity, classification, packing, quantity, and safety information relating to the dangerous cargo. The declaration allows the carrier and ship master to decide whether the cargo may be accepted and where it may be safely stowed.

A Dangerous Goods Declaration usually includes the shipper’s details, consignee’s details, Proper Shipping Name, UN Number, hazard class, subsidiary risk, packing group, number and type of packages, quantity, flashpoint where applicable, marine pollutant status, emergency contact details, and a signed shipper’s certification that the cargo is correctly classified, packed, marked, labelled, and in proper condition for carriage.

The duty to prepare and submit the Dangerous Goods Declaration rests primarily with the shipper. The shipper is the party that knows or should know the real nature of the cargo. The carrier, shipowner, charterer, and ship master rely on the shipper’s declaration, but they should not ignore warning signs. If cargo descriptions are vague, inconsistent, commercially unusual, or unsupported by proper documents, further inquiry is necessary before loading.

Marking, Labelling, and Placarding of Dangerous Goods

Marking, labelling, and placarding are essential because they allow everyone in the transport chain to identify hazards quickly. A dangerous goods package or container must display the correct hazard labels and marks, including the UN Number and any marine pollutant mark where required. Container placards must correspond with the dangerous goods inside.

Incorrect or missing labels can cause serious operational problems. Cargo handlers may stow the cargo in the wrong place, incompatible dangerous goods may be placed together, emergency responders may apply the wrong firefighting method, and port authorities may detain the cargo or ship. For this reason, visual checks of packages, containers, marks, placards, and documents should be part of the dangerous goods acceptance process.

Stowage and Segregation under the IMDG Code

Stowage and segregation are among the most important operational parts of the IMDG Code. Some dangerous goods must be kept away from accommodation spaces, sources of heat, foodstuffs, living quarters, machinery spaces, or other sensitive areas. Others must not be stowed together because they may react dangerously if leakage, fire, or contamination occurs.

Segregation requirements are designed to prevent incompatible substances from interacting. For example, acids may need to be segregated from alkalis, oxidizing substances from flammable materials, and water-reactive cargoes from sources of moisture. In container shipping, segregation must be considered not only inside individual containers but also between containers and within the whole stowage plan.

The ship master and officers must have access to accurate cargo information before loading so that dangerous goods can be placed in the correct location. Late or incorrect dangerous goods information may cause cargo restowage, port delay, additional costs, and disputes between shipowners, charterers, shippers, and terminals.

IMDG Code and Dangerous Dry Bulk Cargoes

The IMDG Code primarily governs dangerous goods in packaged form. Dangerous solid bulk cargoes carried without packaging are generally regulated by the International Maritime Solid Bulk Cargoes Code (IMSBC Code). This distinction is important in dry bulk shipping because many hazardous cargoes are carried loose in bulk rather than in packages or containers.

Dangerous dry bulk cargoes may present risks such as liquefaction, self-heating, oxygen depletion, toxic gas emission, corrosive action, fire, explosion, or dangerous reaction with water. Examples may include certain coal cargoes, metal sulphide concentrates, seed cake, direct reduced iron, sulphur, fertilizers, ores, and cargoes liable to emit toxic or flammable gases.

For dangerous dry bulk cargoes, the shipper must provide correct cargo information and any required certificates under the IMSBC Code. Depending on the cargo, this may include moisture content, Transportable Moisture Limit, chemical properties, ventilation requirements, trimming requirements, and emergency precautions. The ship master should not accept dangerous bulk cargo unless the cargo is properly declared and the ship can carry it safely.

Misdeclaration of Dangerous Cargoes

Misdeclaration is one of the most dangerous problems in maritime transport. A shipper may wrongly describe dangerous cargo as harmless cargo, use an incorrect trade name, omit a UN Number, hide the cargo’s hazardous properties, or provide documents that do not match the cargo actually presented for shipment. Misdeclaration can be accidental, but it may also be deliberate to avoid higher freight, special handling costs, rejection by carriers, or regulatory restrictions.

Misdeclared dangerous goods can expose the ship to catastrophic risk. If a cargo is wrongly declared, it may be stowed near incompatible cargo, placed close to heat sources, loaded in a hold without proper ventilation, accepted on a ship lacking the necessary equipment, or handled by crew who have not been warned of the danger. A fire or chemical reaction involving misdeclared dangerous goods can spread quickly and become extremely difficult to control at sea.

Shipowners and charterers should be alert to warning signs such as unfamiliar shippers, vague cargo descriptions, unusual routing, inconsistent documents, missing safety data, pressure to load quickly, reluctance to provide samples, and refusal to allow independent inspection. When doubt exists, the safer course is to delay loading until the cargo is properly identified and documented.

What Can Shipowners Refuse to Carry?

Shipowners may refuse cargo that is outside the charterparty description, prohibited by the contract, unlawful, unsafe, misdeclared, improperly packed, inadequately documented, or unsuitable for the ship. Even where charterers have employment rights under a time charterparty, those rights do not permit orders that expose the ship to an unsafe or illegal voyage.

Before entering a charterparty, shipowners should consider whether dangerous goods will be permitted and, if so, under what conditions. Long-term time charterparties require particular care because the ship may be employed in many trades over a long period. Instead of relying on general wording, shipowners may choose to list prohibited cargoes, require prior approval for dangerous goods, or identify only the cargoes that may be carried without further consent.

Where dangerous goods are accepted, the shipowner should confirm that the ship has suitable firefighting arrangements, ventilation, segregation capability, emergency equipment, crew training, and documentary support. Smaller ships may have limited space for safe segregation, and some ships may not be suitable for certain classes or quantities of dangerous goods.

Ship Master’s Role in Dangerous Goods Carriage

The ship master plays a critical role in protecting the ship, crew, and cargo. The ship master must be given sufficient information before loading to make safe operational decisions. If dangerous goods are not properly declared or appear unsafe, the ship master may need to stop loading, request clarification, demand further documents, consult the shipowner or P&I Club, or refuse the cargo.

The ship master and officers should know where dangerous goods are stowed, what hazards they present, how they should be monitored, and what emergency procedures apply. Crew members should receive relevant information before loading and should understand the early warning signs of leakage, heating, gas emission, smoke, abnormal smell, container damage, or cargo instability.

Dangerous goods must not be treated as an administrative matter only. The documents are important, but the physical condition of the cargo, packaging, container, markings, and stowage arrangement must also be checked where possible. A document stating that cargo is safe does not cure visible leakage, damaged packaging, wrong labels, or unsafe stowage.

Emergency Response and Crew Preparedness

Emergency preparedness is essential when dangerous goods are carried by sea. The crew should have access to emergency schedules, medical first aid guidance, firefighting instructions, spill control equipment, personal protective equipment, and communication procedures. Drills and briefings are especially important when the ship carries cargoes with fire, toxicity, corrosive, or gas emission risks.

Response time at sea may be long, and external assistance may not be available quickly. Therefore, the ship must be prepared to manage the first stage of any dangerous goods incident independently. Early detection and correct action can prevent a manageable incident from becoming a major casualty.

Dangerous goods emergency planning should consider fire, explosion, toxic exposure, marine pollution, container leakage, cargo reaction, crew injury, port refuge, and the possibility that cargo may need to be isolated, cooled, jettisoned, discharged, or otherwise rendered harmless in accordance with law and the ship master’s authority.

Insurance and P&I Club Considerations

The carriage of dangerous goods can affect insurance and P&I Club cover. A shipowner should not assume that insurance will respond if the ship knowingly carries dangerous goods in breach of law, class requirements, charterparty restrictions, or safety regulations. Some policies may contain express warranties or conditions dealing with dangerous cargoes. Even where no express warranty exists, a substantial change in trading pattern or risk profile may need to be disclosed to insurers.

If a ship changes from carrying ordinary dry cargo to carrying significant quantities of dangerous goods, the shipowner should consider whether this alters the insured risk. The shipowner should also check whether the ship has the required certification, equipment, crew competence, and operational procedures. P&I Club guidance should be obtained where cargo risk, documentation, or charterparty wording is uncertain.

From a claims perspective, dangerous goods incidents often create disputes over misdeclaration, seaworthiness, cargoworthiness, stowage responsibility, charterers’ orders, shipper liability, Hague-Visby Rules, general average, salvage, pollution, port costs, cargo damage, and delay. Clear documents and early advice are essential.

Dangerous Goods, Delay, Demurrage, and Port Problems

Dangerous goods non-compliance can cause serious delay. A port may refuse entry, require restowage, demand additional documents, order cargo inspection, impose fines, require discharge, or detain the ship until safety concerns are resolved. If containers or packages are incorrectly declared or damaged, terminals may refuse to handle them.

In chartering, these delays may lead to demurrage, detention, deviation costs, loss of laytime, off-hire disputes, freight disputes, and claims for additional expenses. The allocation of these costs depends on the charterparty wording, the cause of the delay, the party responsible for the cargo information, and whether the shipowner or charterer failed to comply with applicable duties.

For that reason, dangerous goods clauses should be connected with demurrage, detention, indemnity, delay, port charges, and cargo rejection provisions. The contract should make clear who bears the time and cost consequences if dangerous goods are misdeclared, wrongly packed, improperly labelled, rejected by authorities, or found unsafe after loading.

Practical Precautions Before Accepting Dangerous Goods

Before accepting dangerous goods, shipowners, operators, and charterers should consider the following practical safeguards:

Identify the Shipper: check the shipper’s reputation, history, and experience with dangerous goods.
Confirm the Cargo: obtain the Proper Shipping Name, UN Number, hazard class, packing group, quantity, packaging, and safety data.
Check the Contract: confirm whether the charterparty permits or excludes the cargo.
Verify Ship Suitability: ensure the ship has the required equipment, space, certificates, and segregation capability.
Review Documentation: examine the Dangerous Goods Declaration, safety data sheets, certificates, and port documents.
Inspect Where Possible: check packaging, containers, marks, labels, placards, and cargo condition.
Plan Stowage Early: confirm segregation, ventilation, deck or underdeck stowage, and emergency access.
Consult Experts: involve the P&I Club, technical consultants, surveyors, or dangerous goods specialists when needed.
Brief the Crew: ensure officers and crew understand the cargo hazards and emergency procedures.
Refuse Unsafe Cargo: do not load cargo that is misdeclared, undocumented, leaking, damaged, or outside the ship’s capability.

Why the IMDG Code Matters in Modern Shipping

The IMDG Code matters because dangerous goods are carried daily in global trade, often inside containers or packages that may not reveal their true risk from outward appearance. A single undeclared or wrongly stowed dangerous cargo can endanger an entire ship. The IMDG Code provides the common rules needed to prevent such risks from becoming casualties.

For shipowners, the IMDG Code helps protect the ship, crew, and commercial position. For charterers, it helps ensure that cargo can be shipped lawfully and without avoidable delay. For shippers, it defines the minimum standard for correct classification, packing, marking, documentation, and declaration. For ship masters, it provides the information needed to make safe operational decisions.

In both containerized and dry cargo trades, dangerous goods must be approached with caution, accurate information, and disciplined compliance. Safe carriage depends on honest declarations, competent packing, correct documentation, careful stowage, proper segregation, trained crew, and clear contractual allocation of responsibility. When these safeguards are ignored, the consequences can be severe. When they are applied correctly, dangerous goods can be transported safely and efficiently as part of normal maritime trade.