IMDG Code Classification: Classes 1–9 Explained And Examples

Categories
Recent Posts

IMDG Code classification is the system the shipping industry uses to group dangerous goods by the primary risk they present at sea. Set by the International Maritime Organization, it divides hazardous materials into nine classes (from explosives to miscellaneous hazards) and dictates how each must be packaged, labelled, documented, stowed and segregated on a vessel. Getting the class right isn’t just a paperwork exercise; it determines your UN number, packing and quantity limits, the marks and placards you need, and ultimately whether your shipment moves safely and lawfully.

This guide explains Classes 1–9 in plain English, with the key criteria, divisions and everyday examples you’ll recognise (think paints, aerosols, lithium batteries, peroxides and dry ice). You’ll learn how to identify the correct class from a Safety Data Sheet and the Dangerous Goods List, what the hazard labels mean, how packing groups, limited and excepted quantities work, and what to do about marine pollutants and materials hazardous only in bulk. We’ll also outline stowage and segregation basics and the core documents you must issue (including the DGD and container packing certificate). Let’s start with how classification works and how to identify your class.

How classification works and how to identify your class

IMDG Code classification starts by matching your product to a UN entry that reflects its primary hazard at sea. You use objective properties (e.g., flammability, toxicity, oxidising behaviour, reactivity with water) and any available test data. The outcome sets the class/division and any subsidiary risks, which then drive packaging, quantity limits, marks and stowage.

  • Find the UN entry: Take the UN number and Proper Shipping Name from the SDS (often Section 14) or determine them using test data.
  • Verify in the IMDG Dangerous Goods List: Confirm the Class/division, subsidiary hazard(s), and—where applicable—the Packing Group.
  • Check special instructions: Review special provisions, limited/excepted quantity allowances, EmS Guide codes, and stowage/segregation requirements.
  • Assess environment-specific flags: Identify if the substance is a marine pollutant (Class 9 if otherwise not dangerous) or an MHB when shipped in bulk only.
  • Handle mixtures and N.O.S. entries: If not named, choose the most appropriate “N.O.S.” entry by predominant hazard and add required technical names.
  • Classify articles by entry: Use article-specific entries (e.g., aerosols, batteries, gas cartridges) rather than raw substance criteria.

Class 1: explosives – divisions and examples

IMDG Class 1 covers substances and articles with explosive effects. The Code divides them into six divisions that determine stowage, segregation, quantity limits and emergency actions at sea.

  • 1.1: Mass explosion
  • 1.2: Projection hazard
  • 1.3: Fire with minor blast/projection
  • 1.4: No significant hazard
  • 1.5: Very insensitive, mass explosion
  • 1.6: Extremely insensitive, no mass explosion

Typical examples: dynamite, fireworks and ammunition.

Class 2: gases – divisions and examples

Class 2 covers gases that are compressed, liquefied or dissolved under pressure. Hazards include fire, explosion, asphyxiation and toxicity, so the IMDG Code separates them into three divisions.

  • 2.1 Flammable gases: Propane, butane, hydrogen.
  • 2.2 Non-flammable gases: Nitrogen, carbon dioxide, argon.
  • 2.3 Toxic gases: Chlorine, ammonia.

Common articles: aerosols and gas cartridges.

Class 3: flammable liquids – criteria and examples

Under IMDG Code classification, Class 3 covers liquids and liquid mixtures that emit flammable vapours and can ignite during transport. Criteria rely on flash point and initial boiling point, which set the packing group, limited/excepted quantity allowances, and stowage precautions.

  • Petrol/gasoline, ethanol and methanol.
  • Solvent-based paints, varnish and adhesives.
  • Acetone (e.g., nail polish remover).

Class 4: flammable solids – divisions and examples

Class 4 covers solids that ignite readily or generate flammable gases, creating major fire hazards on board. IMDG Code classification splits them by ignition behaviour and reaction with air or water.

  • 4.1 Flammable solids: matches, magnesium.
  • 4.2 Substances liable to spontaneous combustion: white phosphorus.
  • 4.3 Substances which, in contact with water, emit flammable gases: sodium, calcium carbide.

Class 5: oxidising substances and organic peroxides – subdivisions and examples

Class 5 covers oxidisers that feed fire and organic peroxides that can decompose violently. IMDG Code classification splits them into two subdivisions; both require temperature control and segregation from combustibles because they intensify burning and can self‑accelerate.

  • 5.1 Oxidising substances: Hydrogen peroxide solutions, potassium nitrate, sodium chlorate.
  • 5.2 Organic peroxides: Formulations that may burn rapidly and are sensitive to impact or friction (e.g., curing agents for resins).

Class 6: toxic and infectious substances – subdivisions and examples

Class 6 covers toxic chemicals and infectious materials that threaten human health. IMDG Code classification splits it into 6.1 toxic substances and 6.2 infectious substances; both demand secure packaging and marking to avoid exposure at sea.

  • 6.1 Toxic substances: cyanide, arsenic compounds, pesticides. Hazard: poisoning.
  • 6.2 Infectious substances: diagnostic specimens, clinical waste, cultures. Hazard: infection.

Class 7: radioactive material – categories and examples

Class 7 covers materials that emit ionising radiation. Under IMDG Code classification these are shipped in defined package categories (for example, excepted packages and Type A or Type B packages), with additional controls for fissile material. The aim is to limit dose rates and prevent any release in transport. Typical examples include uranium and plutonium in the fuel cycle, and medical isotopes such as radioactive iodine.

Class 8: corrosive substances – criteria and examples

Class 8 covers substances that severely damage living tissue and corrode metals. Under IMDG Code classification, assignment hinges on skin‑corrosion tests and attack on steel or aluminium, with Packing Groups I–III reflecting severity. Segregate incompatible substances and prevent leaks. Examples: sulfuric acid, hydrochloric acid, sodium hydroxide.

Class 9: miscellaneous dangerous substances and articles – common items

Class 9 in the IMDG Code covers miscellaneous hazards that don’t fit Classes 1–8 and includes environmentally hazardous substances otherwise not regulated. Controls are UN‑entry specific—always confirm packaging, marking and stowage in the Dangerous Goods List.

  • Lithium batteries (UN 3480/3481; UN 3090/3091).
  • Dry ice/Carbon dioxide, solid (UN 1845).
  • Environmentally hazardous substance N.O.S. (UN 3077/3082).

Marine pollutants and materials hazardous only in bulk (MHB)

Some dangerous goods are regulated because of their impact on the marine environment rather than an acute fire or toxicity risk. Under IMDG Code classification, substances identified as marine pollutants are listed in Class 9 when they are not otherwise dangerous, and are shipped under appropriate UN entries (often N.O.S.). Materials hazardous only in bulk (MHB) are flagged for bulk carriage only; the specific MHB rules do not apply when moved in closed freight containers, though prudent precautions may still be required.

Marking, labelling and placarding at sea

Clear, compliant identification links the package, the cargo transport unit (CTU) and the ship’s manifest. Under IMDG Code classification you must display the correct hazard label(s) for the class and any subsidiary risk, show the Proper Shipping Name and UN number, and apply any additional marks. CTUs (e.g., containers) require placards with the class symbol and the UN number visible on all four sides.

  • UN number and Proper Shipping Name: e.g., UN 1993 FLAMMABLE LIQUID, N.O.S.
  • Primary and subsidiary hazard labels: Class diamonds as specified.
  • Marine pollutant mark: Where applicable on packages and CTUs.
  • Limited Quantity mark: When shipped under LQ provisions.
  • Orientation arrows: For liquids in combination packagings.
  • Overpack mark: When packages are combined and labels/marks are obscured.
  • Elevated temperature mark: For substances shipped hot.
  • Fumigation warning sign: When the CTU has been fumigated.

Packing groups, limited quantities and excepted quantities

Once you’ve identified the correct UN entry via IMDG Code classification, the Dangerous Goods List tells you three levers that change how you pack and declare the goods: any Packing Group (PG), Limited Quantities (LQ) authorisation, and Excepted Quantities (EQ). These set performance levels for packaging and the size limits for inner/outer packagings, as well as the marks you must apply.

  • Packing Groups (PG): If assigned, PG I–III indicate the degree of danger and the required packaging performance.
  • Limited Quantities (LQ): Small retail‑type pack sizes permitted under specified inner/outer limits and the LQ mark.
  • Excepted Quantities (EQ): Very small inner quantities under strict set sizes, with the EQ mark; carrier conditions still apply.

Stowage, segregation and compatibility basics

Stowage under the IMDG Code is about preventing fires, leaks, gas build‑up and dangerous reactions at sea. Each UN entry in the Dangerous Goods List specifies stowage and segregation instructions; follow those, not assumptions based on class alone. Use them alongside EmS Guide codes to plan where cargo sits on board and what must be kept apart.

  • Check the UN entry: Apply the listed stowage/segregation codes and any special provisions.
  • Segregate incompatibles: Keep oxidisers (5.1) away from flammables (3/4.1); keep 4.3 strictly dry and away from water sources.
  • Control the atmosphere: Provide ventilation for gases (2) and volatile liquids (3); control temperature for peroxides (5.2).
  • Secure and protect: Lash to prevent movement, keep away from heat/ignition, and protect from physical damage.
  • Plan for emergencies: Maintain access routes and the specified fire‑fighting and spill gear for the EmS response.

Documentation you need for sea freight (DGD, CPC, MDGF)

Paperwork is the proof that your IMDG Code classification, packing and marking have been done correctly, and it equips the vessel and authorities with the information they need in an emergency. Prepare it accurately, sign where required, and ensure details match the packages and placards on your cargo transport unit.

  • Dangerous Goods Declaration (DGD): Completed by the shipper; shows UN number/Proper Shipping Name, class/division, subsidiary risks, packing group (if any), quantities/packaging, marks/labels, and marine pollutant status, plus shipper/consignee details.
  • Container/Vehicle Packing Certificate (CPC/CVPC): Signed by the packer; confirms the CTU was packed, secured, segregated and marked/placarded in full IMDG compliance.
  • Multimodal Dangerous Goods Form (MDGF): The standard IMO/ILO/UNECE model form that combines the DGD and the CPC on one document for door‑to‑door moves.
  • Dangerous goods manifest (ship copy): Compiled from your DGDs by the carrier/ship; keep your documents consistent with the sailed manifest.
  • Supporting approvals (as required): Any exemption/authorisation letters and special temperature or handling instructions requested by the carrier or competent authority.

Training and certification for IMDG compliance

The IMDG Code requires anyone preparing, offering, accepting or handling dangerous goods for sea to be trained appropriate to their duties—before they perform the function—and retrained when rules or roles change. Training must cover general awareness, function-specific and safety, with records kept for inspection. Practical, scenario‑based courses (classroom, e‑learning, virtual or in‑house) build confidence for shippers, packers, CTU packers, freight forwarders and port/line staff.

Key takeaways

Getting IMDG classification right sets everything else on the voyage: the correct UN entry, class/division and any subsidiary risks dictate how you pack, mark, document, stow and segregate your cargo. Always verify the UN entry in the Dangerous Goods List, apply the right marks and placards, and confirm whether marine pollutant or MHB rules apply. Then align packaging choices (PG, LQ, EQ) with stowage/segregation instructions and complete robust documentation and training.

  • Class drives compliance: Class/division and subsidiary risks determine every downstream requirement.
  • Use the DGL: Confirm UN entry details, special provisions and EmS guidance.
  • Mark, label, placard: Show UN number/PSN, primary/subsidiary labels and any extra marks.
  • Choose packing route: Apply PG, LQ or EQ correctly and within limits.
  • Plan stowage/segregation: Follow the UN entry codes; keep incompatibles apart.
  • Get the paperwork right: DGD plus CPC/CVPC (often on the MDGF).

Need clarity or team training? Speak to the experts at Logicom Hub for practical, compliant IMDG dangerous goods training and support.