For anyone managing or operating vessels that transport goods by sea, ensuring safety and maintaining compliance are top priorities. When your cargo includes potentially hazardous materials, the stakes become even higher. A single mistake can lead to catastrophic accidents, environmental damage, and severe legal penalties. The key to preventing such outcomes is a thorough understanding of the International Maritime Dangerous Goods (IMDG) Code.

Navigating the IMDG guidelines can seem complex, but having the right information and resources makes all the difference. Our guide provides a straightforward look at the IMDG code, breaking down the IMDG code classes and outlining the steps needed to keep your operations safe and compliant.

What is the IMDG Code and Why is Compliance Critical?

The IMDG Code is the globally accepted standard for the safe transportation of dangerous goods and marine pollutants by sea. Created by the International Maritime Organization (IMO), the code establishes a uniform set of rules that govern how hazardous cargo codes are classified, packed, marked, labeled, stowed, and documented. The IMDG meaning is rooted in universal safety and standardization.

Compliance is not optional. The IMDG code is enforced under two major international treaties: the International Convention for the Safety of Life at Sea (SOLAS) and the International Convention for the Prevention of Pollution from Ships (MARPOL). For the 175 IMO member states, this makes the code a mandatory legal requirement.

Failure to comply can result in port state control detentions, massive fines, and rejected shipments, causing costly operational delays. More importantly, non-compliance puts your crew, vessel, and the marine environment at serious risk. Research into maritime accidents has repeatedly shown that strict adherence to safety codes like the IMDG code is fundamental to preventing incidents (Celik & Cebi, 2009).

To ensure full compliance, your vessel must carry the latest edition of the official IMDG code book. The code is published in a two-volume set with a separate, essential supplement.

• The Core Rulebook: The definitive guide you need is the IMDG Code, Amendment 42-24, 2024 Edition. Volume 1 covers general provisions, training requirements, classification criteria, and consignment procedures. Volume 2 contains the Dangerous Goods List (DGL) , a detailed table of thousands of substances with their UN numbers, proper shipping names, and specific transport requirements.

• The Essential Supplement: The IMDG Code Supplement, 2024 Edition is a required companion. A crucial part of the IMDG code book, it contains the Emergency Response Procedures (IMDG Code EMS Guide), the Medical First Aid Guide (MFAG), and other critical safety procedures. You cannot be fully compliant without having this supplement on board.

As an ISO 9001 certified company and a top distributor for IMO publications, American Nautical Services provides the authentic, official publications you need to guarantee compliance .

What Are the 9 IMDG Code Classes of Hazardous Materials?

The IMDG code organizes hazardous materials into nine distinct classes of IMDG based on the primary danger they pose. Some IMDG classes are broken down further into divisions for greater specificity. A clear understanding of these IMDG code classes is the first step for any crew member or shore-side personnel handling hazmat.

Class 1: Explosives These are substances with an explosion hazard. Improper handling can lead to devastating consequences for the vessel and crew.

• Division 1.1: Mass explosion hazard (e.g., dynamite).

• Division 1.2: Projection hazard (e.g., certain ammunition).

• Division 1.3: Fire hazard with minor blast/projection (e.g., some fireworks).

• Division 1.4: Minor explosion hazard (e.g., consumer fireworks).

• Division 1.5: Very insensitive substances with a mass explosion hazard.

• Division 1.6: Extremely insensitive articles.

Class 2: Gases Gases are defined as substances that are completely gaseous at 20°C or have a vapor pressure of 300 kPa or more. A leak can create a flammable, toxic, or asphyxiating atmosphere.

• Division 2.1: Flammable gases (e.g., propane).

• Division 2.2: Non-flammable, non-toxic gases (e.g., carbon dioxide, nitrogen).

• Division 2.3: Toxic gases (e.g., ammonia, chlorine).

Class 3: Flammable Liquids This class covers liquids that give off flammable vapors. A spill in a poorly ventilated area can create a highly combustible environment, posing a severe fire risk.

• Examples: Gasoline, ethanol, paints, acetone.

Class 4: Flammable Solids & Other Combustible Materials A diverse class covering substances that can ignite easily or react dangerously.

• Division 4.1: Flammable solids (e.g., matches, sulfur).

• Division 4.2: Substances liable to spontaneous combustion (e.g., oily cotton waste).

• Division 4.3: Substances that emit flammable gas when in contact with water (e.g., calcium carbide).

Class 5: Oxidizing Substances and Organic Peroxides These substances may not be combustible themselves, but they can yield oxygen and cause or contribute to the combustion of other materials.

• Division 5.1: Oxidizing substances (e.g., ammonium nitrate).

• Division 5.2: Organic peroxides, which are often thermally unstable.

Class 6: Toxic and Infectious Substances Substances that can cause serious injury or death upon contact, inhalation, or ingestion. Exposure can have immediate or long-term health effects on the crew.

• Division 6.1: Toxic substances (e.g., pesticides, mercury compounds).

• Division 6.2: Infectious substances (e.g., medical waste, lab cultures).

Class 7: Radioactive Material Materials containing radionuclides. Transport is highly regulated due to the danger of radiation exposure.

• Examples: Medical isotopes, industrial gauges.

Class 8: Corrosive Substances Substances that cause severe damage to living tissue or can materially damage the vessel's structure upon leakage. A spill can eat through steel decks and compromise ship integrity.

• Examples: Sulfuric acid, sodium hydroxide (caustic soda), batteries.

Class 9: Miscellaneous Dangerous Substances and Articles A catch-all class for hazards not covered elsewhere. This class has grown in importance with the rise of new technologies.

• Examples: Lithium-ion batteries, dry ice, asbestos, and materials classified as marine pollutants.

For quick reference on the bridge or in the planning office, the Storck Guide: IMDG Code at a Glance 2024 is an invaluable tool that summarizes the key data for each class. We also carry the 2024 edition of the Storck Guide for your reference needs. 

How Can You Implement the IMDG Code for Full Compliance?

Implementing the IMDG code across your organization is a systematic process. Effective implementation relies on having the right resources, ongoing training, and clear internal procedures. Studies have shown that a strong safety culture, driven by management and continuous education, is key to successful code implementation (Ghani, 2013).

Here is a practical, step-by-step approach for captains and fleet managers to ensure compliance.

Step 1: Obtain All Required Regulatory Publications

You cannot follow rules you do not possess. The foundation of any compliance program is having the current, official regulatory texts on board. The IMDG code is amended every two years, so using an outdated IMDG book is a direct path to non-compliance. (The IMDG Code is valid for 3 years)

• Action: Equip your vessels with the complete set of required publications. The American Nautical Services IMDG Code collection has all the official IMO books you need in one place.

Step 2: Train Your Personnel

The IMDG code mandates that all personnel involved in transporting dangerous goods both shipboard and shore-based must receive training appropriate to their duties. This includes staff who classify goods, pack containers, prepare documentation, and handle cargo on the vessel.

• Action: Ensure your team is properly trained. American Nautical Services offers hazmat transportation consulting to help you identify and fulfill your training obligations.

Step 3: Master Consignment Procedures

This is the hands-on part of compliance, where cargo is prepared for shipment.

• Classify: Use the criteria in the IMDG code book to correctly identify the UN number, proper shipping name, class, and packing group for your goods.

• Package: Use only UN-approved packaging that meets the required performance standards for the substance being shipped.

• Mark and Label: The package must be marked with the UN number and proper shipping name. The correct hazard labels for the primary and any subsidiary risks must be applied. For cargo transport units like containers, corresponding placards must be displayed.

Step 4: Ensure Accurate Documentation

Every dangerous goods shipment must be accompanied by a Dangerous Goods Declaration (DGD). This legal document, filled out by the shipper, provides the master with complete information about the cargo. Any error on the DGD can lead to the shipment being rejected.

Step 5: Consolidate Your Regulatory Resources

Operations are rarely limited to one set of rules. If you call on U.S. ports, you must also comply with the U.S. Department of Transportation's hazardous materials regulations, found in Title 49 of the Code of Federal Regulations (49 CFR). If you also ship via air, you need the IATA Dangerous Goods Regulations (DGR).

• Action: Simplify your compliance library with our convenient bundles.

• For U.S. voyages, the IMDG Code + 49 CFR + ERG bundle provides a comprehensive solution.

• For multi-modal shipping, the IATA DGR + IMDG Code bundle ensures you are covered for both sea and air transport.

The IMDG definition of safety is comprehensive. Partnering with a knowledgeable supplier like American Nautical Services gives you more than just publications; you get a dedicated partner in safety and compliance. If you have questions about your vessel's specific needs, contact our team of specialists today.

Frequently Asked Questions

Q. What is the difference between the IMDG Code and the IMDG Code EMS?
The IMDG Code is the overall set of regulations for transport. The IMDG Code EMS Guide, found in the Supplement, provides specific Emergency Response Procedures for incidents involving dangerous goods, guiding the crew on what to do in case of a fire or spillage.

Q. What does "marine pollutant" mean in the IMDG Code?
A marine pollutant is a substance identified in the IMDG Code that is harmful to the marine environment. These goods have specific stowage and documentation requirements to prevent pollution.

Q. Who is responsible for classifying dangerous goods?
The shipper (or consignor) is primarily responsible for correctly classifying dangerous goods according to the criteria laid out in the IMDG code.

Q. Can I use an old version of the IMDG book?No. The IMDG code is updated every two years, and using an outdated version will make you non-compliant. There is a one-year transitional period where the old or new amendment may be used, but after that, only the latest amendment is valid. Each edition is valid for 3 years

Q. What is a UN Number?
A UN Number is a four-digit number assigned by the United Nations Committee of Experts on the Transport of Dangerous Goods. Each number identifies a specific hazardous substance or group of substances, allowing for universal recognition worldwide.