IMDG Class 9: Miscellaneous Dangerous Goods

Background

Why Class 9 exists at all

The International Maritime Dangerous Goods Code (IMDG Code), like its parent the United Nations Recommendations on the Transport of Dangerous Goods (the so-called Orange Book) and the modal codes derived from it (ICAO Technical Instructions for air, ADR for road, RID for rail), organises hazardous goods into nine classes based on the dominant physical or chemical hazard. Eight of those classes describe a single coherent hazard: explosives (Class 1) self-detonate or self-ignite from chemical instability; gases (Class 2) present pressure, asphyxiation or toxicity hazards by virtue of their gaseous state; flammable liquids (Class 3) ignite below a defined flash point; flammable solids, self-reactives and pyrophoric or water-reactive substances (Class 4) ignite under specific environmental conditions; oxidisers and organic peroxides (Class 5) accelerate combustion or self-decompose; toxic and infectious substances (Class 6) cause harm by inhalation, ingestion or skin contact; radioactive material (Class 7) emits ionising radiation; and corrosives (Class 8) destroy living tissue and damage other materials by chemical attack.

Class 9 is the catch-all for substances and articles that nevertheless present a real transport hazard but do not fit any of the eight defining hazard classes. The drafters of the UN Model Regulations recognised early on that some cargoes, while genuinely dangerous, did not fit neatly into any of the eight existing categories: a lithium-ion battery, for example, is not strictly an explosive, not a gas, not a flammable liquid in itself, not a self-reactive solid, not an oxidiser, not toxic, not radioactive and not (typically) corrosive, yet its potential for thermal runaway makes it one of the most hazardous cargoes a container ship can carry. Marine pollutants are a similar case: a substance may be perfectly benign in terms of fire, explosion and toxicity to humans, yet its release into the marine environment causes serious ecological damage. Class 9 was created to give such substances a regulatory home.

Class 9 as the modern container ship’s biggest risk

Class 9 was historically considered a low-risk class. That perception changed permanently in the 2010s as the volume of lithium-ion batteries shipped by sea climbed by orders of magnitude, driven by consumer electronics, electric vehicles and grid-scale energy storage. A series of major container-ship fires have since been attributed wholly or partly to lithium-cell thermal runaway: the Maersk Honam in March 2018 (five crew dead; $1.6 billion total loss; declared general average), the Yantian Express in January 2019, the APL Vancouver in January 2019, the MSC Flaminia in 2012 (although that fire’s primary trigger was DVB monomer in IBCs the cargo manifest also included Class 9 items), the Zim Kingston in October 2021, and the X-Press Pearl in May 2021 (a complete loss off Sri Lanka) all involved Class 9 lithium-cell or environmentally-hazardous-substance cargoes either as primary fire source or as fuel-load multipliers. Class 9 today drives container-ship insurance underwriting more than any other single hazard class, and many lines have tightened acceptance criteria, surcharges and stowage practice for UN 3480 and UN 3481 specifically. See container ship for the casualty context.

Class 9 vs MARPOL Annex III

Class 9 is also the principal regulatory bridge between the IMDG Code (which addresses safety of life and ship) and MARPOL Annex III, which addresses marine environmental protection from packaged dangerous goods. A substance that is identified as a marine pollutant under MARPOL Annex III must be transported under the IMDG Code with the marine-pollutant mark, and if it does not meet the criteria for any other IMDG class it is shipped as UN 3077 (environmentally hazardous substance, solid, n.o.s.) or UN 3082 (environmentally hazardous substance, liquid, n.o.s.), which are Class 9 entries. The full list of marine pollutants is maintained in IMDG Code Chapter 2.10 and, on a substance-specific basis, in the Dangerous Goods List (Chapter 3.2). For the operational mechanics of Annex III see MARPOL Annex III. For the ship-side framework that gates dangerous goods carriage in general see SOLAS Chapter VII.

Class 9 vs Class 4.1 self-reactives and Class 5.2 organic peroxides

A common classification confusion is between certain Class 9 polymerising substances and Class 4.1 self-reactive substances. Stabilised polymerising substances (added to the UN Model Regulations in 2017 as UN 3531-3534) are formally Class 4.1, not Class 9, even though they share some operational characteristics with Class 9 elevated-temperature substances. The boundary is whether the substance polymerises exothermically through a self-sustaining reaction (Class 4.1) or whether it is merely carried at elevated temperature without intrinsic self-reactivity (Class 9 UN 3257/UN 3258). Similarly, lithium batteries are sometimes confused with Class 5.2 organic peroxides because both can undergo thermal runaway; the distinction is that organic peroxides decompose chemically due to the intrinsic instability of the -O-O- bond, whereas lithium-cell runaway is triggered by internal short circuit, mechanical damage or external heat exposure rather than by any single self-decomposing molecule.

Lithium batteries: Class 9’s dominant cargo

UN numbers and the four entries

The IMDG Code assigns four UN numbers to lithium cells and batteries:

• UN 3480 Lithium-ion batteries (including lithium-ion polymer batteries) shipped on their own.
• UN 3481 Lithium-ion batteries (including lithium-ion polymer batteries) packed with equipment or contained in equipment.
• UN 3090 Lithium-metal batteries (including lithium alloy batteries) shipped on their own.
• UN 3091 Lithium-metal batteries (including lithium alloy batteries) packed with equipment or contained in equipment.

The chemistry distinction matters: lithium-ion cells use a lithium intercalation compound (typically lithium cobalt oxide, lithium iron phosphate, lithium nickel manganese cobalt oxide and similar variants) and a non-aqueous electrolyte containing lithium hexafluorophosphate dissolved in organic carbonates; the cells are rechargeable. Lithium-metal cells use elemental lithium (or lithium alloy) as the anode; they are typically primary (non-rechargeable) cells used in coin batteries, smoke detectors, military radios, certain medical devices and some specialised industrial applications. Lithium-metal cells in transport-relevant quantities are an even more sensitive thermal runaway risk than lithium-ion because elemental lithium reacts violently with water, including atmospheric moisture, and ignites spontaneously when exposed to air at sufficient surface area. Both chemistries are Class 9; both are subject to UN Manual of Tests and Criteria Section 38.3 transport testing; both have Special Provision 188 which sets the small-cell exemption thresholds; and both are stowed under broadly similar rules.

Section IA, IB and II, the watt-hour rating tiers

The IMDG Code (in alignment with ICAO and IATA for air, where the rules originated) divides lithium-battery shipments into three tiers based on energy content per cell and per battery:

• Section IA, full Class 9 dangerous goods consignment, applicable when the battery exceeds the small-cell thresholds (more than 20 Wh per cell and more than 100 Wh per battery for lithium-ion; more than 1 g lithium content per cell and more than 2 g lithium content per battery for lithium-metal). MDGF, full marking, full labelling, packing instruction P903, full segregation rules apply.
• Section IB, smaller cells but in larger packages: cells of not more than 20 Wh and batteries of not more than 100 Wh, but in packages exceeding the Section II quantity limits (typically more than 10 kg per package). Packing instruction P903 with relaxations.
• Section II, fully exempt from most IMDG provisions provided the cells are below the small-cell thresholds (≤20 Wh per cell, ≤100 Wh per battery for Li-ion; ≤1 g lithium content per cell, ≤2 g per battery for Li-metal) and the package weight is below the Section II limit. The package must still bear the lithium battery handling mark (the diamond-shaped label depicting two batteries) and the air waybill or transport document must include certain handling instructions, but no MDGF is required for the maritime mode.

The result is that the same physical product (a smartphone, a laptop, a power tool) can be shipped under Section II with minimal documentation, whereas a pallet of the same product packed for industrial supply may trigger Section IB or IA. Carriers’ booking systems must distinguish the three sections at booking time because the Class 9 segregation rules and stowage limits apply only to Section IA and IB consignments. The IMDG limited quantity calculator supports the small-quantity threshold check.

UN 38.3 testing and the 30% state-of-charge rule

Every lithium cell or battery design intended for international transport must be tested to UN Manual of Tests and Criteria Section 38.3, an eight-test sequence that includes altitude simulation, thermal cycling, vibration, shock, external short circuit, impact/crush, overcharge and forced discharge. The test report must be available on demand and is referenced by the consignor’s certification on the MDGF. Cells that have not been tested cannot be shipped as Section IA, IB or II, they fall under the more restrictive damaged or defective lithium battery entries (UN 3090/3091/3480/3481 with packing instruction P911 and special provision 376) and require approval from the competent authority of the country of origin.

ICAO and IATA introduced a 30% state-of-charge (SoC) limit for lithium-ion batteries shipped by air as cargo (effective 1 April 2016 under the Lithium Battery Guidance Document). The IMDG Code does not impose an explicit SoC limit for sea transport, but most carriers and many shippers apply the 30% SoC rule voluntarily for sea cargo as a conservative practice, particularly for transhipment cargo that may also be carried by air. A battery at 30% SoC has substantially less stored chemical energy available for thermal runaway than a battery at 100% SoC, and the energy released during runaway scales roughly linearly with SoC over the operational range.

Damaged, defective and waste lithium batteries

The most hazardous lithium-battery cargoes are those identified as damaged, defective or waste:

• Damaged or defective cells/batteries that are likely to liberate dangerous quantities of heat, are showing signs of impact damage (dented casing, leaked electrolyte, swollen pouch cells), or have been recalled by the manufacturer for safety reasons. Special Provision 376 applies; packing instruction P911 mandates a package designed to contain a thermal runaway event without external propagation, including thermal-insulation testing and active fire-suppression where required for larger consignments. Approval from the competent authority of the country of origin is mandatory.
• Waste lithium batteries collected for recycling. Special Provision 377 and packing instruction P909 (large-quantity waste shipments) apply. Many recycling operations have moved to dedicated bulk packaging in steel drums with vermiculite or sand cushioning.
• Battery-powered vehicles (UN 3171) carry their lithium battery as a sub-component but are themselves a Class 9 entry covering battery-powered cars, forklifts, motorcycles and similar conveyances. Stowage and segregation reference UN 3171 directly rather than UN 3480.

Stowage and segregation for lithium batteries

In container terms the IMDG Code currently stows Class 9 (including lithium batteries) under stowage category A (any deck or hold, no special restrictions) for most entries, a consequence of Class 9 being the residual class. In practice, however, all major container lines now apply enhanced stowage policies for lithium-battery cargoes: above-deck stowage in accessible bays, separation from heat-generating cargoes, separation from refrigerated containers’ compressors, and avoidance of co-location with reefer cargo demanding constant power feed (which can itself be a fire-initiation source). Some carriers refuse damaged/defective lithium batteries (UN 3480/3090 with SP 376) entirely; others accept them only on dedicated charters. The CINS (Cargo Incident Notification System) industry data show that Class 9 mis-declaration as Class 4 or Class 8 (or as a non-DG cargo) is the single most frequent root cause of container-ship fires investigated since 2018.

For the segregation matrix logic see the IMDG segregation calculator; for the per-class container hazard label specification see the container IMDG class lookup.

Environmentally hazardous substances and marine pollutants

UN 3077 and UN 3082

The two largest UN entries by tonnage in Class 9 (after lithium batteries on a packages-shipped basis) are UN 3077 (Environmentally Hazardous Substance, Solid, n.o.s. and UN 3082) Environmentally Hazardous Substance, Liquid, n.o.s.. These are the residual entries that capture any substance identified as a marine pollutant under MARPOL Annex III for which no more specific UN number applies. They are both Packing Group III (low danger to human health), with EmS F-A and S-F.

How a substance becomes a marine pollutant

The classification criteria for marine pollutants are set out in IMDG Code Chapter 2.10 and align with the Globally Harmonised System (GHS) environmental hazard categories:

• Acute aquatic toxicity Category 1 (acute LC₅₀ or EC₅₀ ≤ 1 mg/L for fish, crustaceans or algae); or
• Chronic aquatic toxicity Category 1 or 2 (chronic NOEC ≤ 0.1 mg/L for non-rapidly degradable substances, or ≤ 1 mg/L with high bioaccumulation potential).

Many heavy-metal compounds, organotin compounds (tributyltin and its analogues), certain pesticides (DDT, PCB-related compounds, lindane) and a wide range of agrochemical formulations qualify. Marine pollutants are identified in the Dangerous Goods List with the letter “P” in column 4. Use the marine pollutant lookup to check whether a specific substance triggers Annex III.

The marine pollutant mark

Packages containing marine pollutants must bear, in addition to the Class 9 label and the UN number, the marine pollutant mark: a black-and-white pictogram showing a dead fish and dead tree on a hatched diamond background. The mark must appear on packages of more than 5 L for liquids or more than 5 kg for solids; smaller quantities are exempt under IMDG 2.10.2.7. The mark must also appear on the container’s exterior on at least two opposing sides. The shipper’s MDGF must declare the marine-pollutant status by adding “MARINE POLLUTANT” to the proper shipping name.

Elevated-temperature substances

UN 3257 and UN 3258

Class 9 also captures substances carried at elevated temperature that are not intrinsically dangerous at ambient conditions but pose a thermal hazard during transport:

• UN 3257 Elevated Temperature Liquid, n.o.s., any liquid carried at or above 100°C and below its flash point if it has one. Typical entries: bitumen and asphalt (carried at 150-180°C), molten sulphur (carried at 130-150°C between its melting point of 113°C and its peak viscosity transition at around 159°C), molten paraffin and waxes, certain molten metal alloys (zinc, aluminium ingot transfer in dedicated tank vessels at 660-720°C, although such cargoes are normally regulated under local rules rather than IMDG).
• UN 3258 Elevated Temperature Solid, n.o.s., any solid carried at or above 240°C. Less common; some metallurgical intermediates fit this entry.

Dedicated tonnage and operational practice

Bitumen carriers and molten-sulphur carriers are highly specialised tonnage. The cargo tanks are heavily insulated and equipped with thermal-oil heating coils to maintain temperature throughout the voyage. The ship’s stability calculation must account for the free-surface effect of partially solidified cargo and for the substantial mass of insulation and heating piping. Loading and discharge are slow operations because the cargo is moved by positive-displacement screw pumps designed for high-viscosity fluid. Crew safety training emphasises steam and sulphur-vapour exposure rather than the chemical hazards typically associated with other classes.

For the cargo-tank arrangements relevant to elevated-temperature liquids see IMDG tank container for the container-cargo case; bitumen is normally carried in dedicated coastal and short-sea tankers rather than in tank containers.

EmS for elevated-temperature substances

EmS schedule F-A (general fire) and S-P (general spillage of high-temperature substances) apply. Fire response is unusual: water cooling of the tank exterior is acceptable but spraying water directly onto a molten cargo can cause a steam explosion, and the recommended response is to allow the cargo to cool naturally while preventing fire spread to surrounding compartments.

Safety devices, magnetised material and other Class 9 articles

UN 3268, safety devices

UN 3268 covers safety devices, electrically initiated containing pyrotechnic substances or hazardous components, designed to function as safety equipment in vehicles and other applications. The largest sub-category is automotive airbag inflators and seatbelt pretensioners, which contain a small charge of energetic material (sodium azide, ammonium nitrate-based propellants, guanidine nitrate composites or similar) designed to deflagrate rapidly to inflate the bag or tension the belt. Bare inflators (not yet installed in a vehicle) are UN 3268; once installed in a finished vehicle the vehicle is shipped under UN 3166 (Vehicles, internal combustion engine) or UN 3171 (Battery-powered vehicle) and the airbags are not separately declared.

Special Provision 280 sets the testing and approval requirements: the device must have been classified by the competent authority based on UN Test Series 6 results showing that it does not present an explosion hazard exceeding Class 9 thresholds. Without that classification the device defaults to Class 1 (explosive), which has dramatically more restrictive shipping rules.

UN 2807, magnetised material

UN 2807 Magnetised Material covers any package whose external magnetic field exceeds the threshold defined in IATA’s air-cargo rules (which the IMDG Code adopted by reference): a magnetic field of more than 0.418 A/m at 2.1 m from any external surface of the package. The hazard is deviation of the vessel’s magnetic compass, which is still a regulatory requirement under SOLAS Chapter V Regulation 19 even on vessels with multiple gyrocompasses, because the magnetic compass is the legal failsafe heading reference.

Typical magnetised material cargoes: industrial rare-earth permanent magnets (neodymium-iron-boron and samarium-cobalt), MRI magnet assemblies, large electric-motor stators and loudspeaker assemblies. Shipper packaging should include magnetic-field shielding (mu-metal or steel boxing) sufficient to bring the external field within the threshold; for cargoes that cannot be shielded below the threshold, stowage at the maximum practical distance from the bridge magnetic compass is required.

UN 1845, dry ice

UN 1845 Carbon Dioxide, Solid (Dry Ice) is a Class 9 entry because solid CO₂ at -78.5°C sublimates directly to gas at atmospheric pressure, displacing oxygen and creating an asphyxiation hazard within enclosed compartments. Dry ice is widely used as a refrigerant for perishables in transit, including pharmaceuticals (notably the cold-chain mRNA vaccines transported globally during 2020-2022) and biological samples. The principal Class 9 controls are:

• The package must be designed to vent CO₂ as it sublimates; sealed pressure-tight packages are not permitted because of the risk of overpressure rupture.
• The shipper must declare the mass of dry ice on the MDGF, because the carrier must verify ventilation in the stowage location is sufficient to keep CO₂ concentration below the asphyxiation threshold.
• For containerised consignments, the carrier should specify above-deck stowage or, if below-deck stowage is necessary, ventilation calculations must be on file.

The Section II small-quantity exemption applies for limited dry-ice quantities used as a refrigerant for non-DG cargo.

UN 2211, polymeric beads, expandable

UN 2211 Polymeric Beads, Expandable are pre-foamed polystyrene beads (used for expanded polystyrene insulation manufacturing) and similar pre-foam materials that contain a residual blowing agent (typically pentane or another C5 hydrocarbon). The blowing agent gradually evolves during storage and transport, creating a flammable atmosphere within the package and the surrounding cargo space. The hazard is moderate at ambient temperature but escalates rapidly above 50°C; stowage away from heat sources is the primary control.

UN 3245, genetically modified organisms and micro-organisms

UN 3245 Genetically Modified Micro-Organisms and UN 3245 Genetically Modified Organisms capture organisms that have been genetically engineered and that are not infectious substances of Category A or B (which would be Class 6.2). Typical shipments are research samples between laboratories. Special Provision 219 and packing instruction P904 apply.

UN 3334 and UN 3335, aviation regulated substances

UN 3334 Aviation Regulated Liquid, n.o.s. and UN 3335 Aviation Regulated Solid, n.o.s. are entries that exist in the IMDG Code only because the substance is regulated for air transport under the ICAO Technical Instructions; they are not actually regulated for sea transport beyond Class 9 marking, and many carriers ship them as non-DG when transhipment to air is not planned.

UN 1374, UN 2211, UN 2212, UN 3072 and other tail entries

A long tail of Class 9 entries covers substances of varied hazard:

• UN 1374 Fishmeal, Class 9 only when the moisture content and antioxidant content fall outside the IMSBC-Code-exempt range; otherwise covered by IMSBC Group B and B (combustible).
• UN 2212 Asbestos, Blue (crocidolite, amosite, anthophyllite, actinolite, tremolite), Class 9 because asbestos fibres themselves are not toxic in transport (the chronic-inhalation risk affects users, not transporters), but spillage requires controlled clean-up. Asbestos shipments have largely ceased due to national bans but legacy and demolition-waste shipments still occur.
• UN 3072 Life-Saving Appliances, not self-inflating, Class 9 because some life-saving appliances contain Class 1, Class 2 or Class 4.1 sub-components (pyrotechnic flares, compressed-gas inflation cylinders, pyrotechnic distress signals); rather than declaring each sub-component, the IMDG Code allows the assembled appliance to be shipped under UN 3072 with the dominant hazard captured.

UN 3166 vehicles and UN 3171 battery-powered vehicles

UN 3166 Vehicles, internal-combustion-engine, flammable-gas-powered or flammable-liquid-powered, and UN 3171 Battery-powered vehicle/equipment are Class 9 entries that capture finished motor vehicles and self-propelled equipment shipped as cargo. RoRo and PCTC trades (pure car and truck carriers; pure car carriers) move millions of UN 3166/UN 3171 units annually between Asian, European and North American ports. The IMDG Code requirements are limited (fuel level reduced as far as practicable, battery disconnected for vehicles not designed to be transported powered, secure stowage), and the bulk of regulatory burden falls on flag-state and class-society standards for ro-ro vessels rather than on per-vehicle IMDG paperwork. See container ship and PCTC tonnage profiles for the operational context.

Stowage and segregation for Class 9 generally

Stowage categories under IMDG Code 7.1

Class 9 entries are individually assigned stowage category in the Dangerous Goods List, but the default for the residual class is category A (any deck or hold, no special temperature, no special distance from sources of heat or living quarters). A small subset of Class 9 entries, notably elevated-temperature substances and certain large lithium-battery consignments, receive category C (on-deck only) or category D (on-deck only with specific restrictions).

In practice, however, commercial container lines have moved well ahead of the IMDG Code minimum for Class 9 lithium-battery cargoes. Most major lines now apply:

• Above-deck stowage for UN 3480/UN 3481 in any quantity.
• Mandatory separation from reefer plugs and power cabling.
• No co-location with Class 4.1 or Class 5.2 cargoes that may also undergo thermal runaway.
• Segregation distance from charcoal, coconut shell carbon and other self-heating IMSBC Group B cargoes.
• Surcharges and additional booking fees that vary by SoC declaration and watt-hour rating.

Segregation matrix

The IMDG Code segregation matrix in Chapter 7.2 sets the minimum required separation between any two classes. Class 9 segregation rules generally allow co-stowage with most other classes, with a few exceptions captured by per-entry segregation codes in the Dangerous Goods List:

• Lithium batteries carry segregation codes that require “separated from” Class 1 (explosives) and Class 5.2 (organic peroxides), and “away from” other Class 9 entries that include incompatible self-heating or self-reactive material.
• Marine pollutants generally segregate from foodstuffs (a non-DG segregation rule from the food-safety regimes) but are otherwise compatible with most cargoes.
• Elevated-temperature substances are kept “away from” all combustibles by virtue of the heat-source nature of the cargo.
• Magnetised material has no formal segregation requirement from the chemical perspective but must be stowed at maximum practicable distance from the magnetic compass.

The IMDG segregation calculator implements the matrix for arbitrary class pairs.

Container labelling and placarding

A Class 9 container must display the Class 9 label (a white square diamond with seven vertical black stripes on the upper half and the figure “9” in black at the lower vertex; the modern variant has a battery icon for lithium-cell consignments, IMDG 5.2.2.2.1.6) on at least two opposing sides plus front and back. The full UN number and proper shipping name must appear in alphanumeric characters at least 65 mm high. For marine pollutants the marine-pollutant mark accompanies the label. For lithium batteries shipped under Section IA or IB the lithium-battery handling mark plus the Class 9 label both appear; under Section II only the lithium-battery handling mark applies.

Emergency response

EmS schedules

The principal EmS schedules applicable across Class 9 entries:

• F-A General fire (apply to most Class 9 fires of low to moderate intensity).
• F-H Fire involving lithium batteries (specific sub-schedule introduced in IMDG Amendment 41-22).
• S-F General spillage of solid material with marine pollutant aspect.
• S-I Specific spillage schedule for lithium batteries with damage and electrolyte leak.
• S-P Spillage of high-temperature substances.

The IMDG EmS lookup returns the applicable schedule for any UN number.

Lithium-battery fire response

Lithium-cell fires involve metal-electrolyte chemistry that is not amenable to conventional fire-fighting tactics:

• Water is the recommended primary medium for lithium-ion battery fires despite the chemical reactivity of lithium with water. The reasoning is that the cooling effect of water (substantial latent heat of vapourisation) reduces the temperature of unaffected cells below the runaway threshold, which dominates over the secondary water-lithium reaction. This is contrary to the older fire-tactics intuition that lithium fires must be handled with dry powder.
• Carbon dioxide flooding is effective for confined-space suppression but not for cooling, so a CO₂ flood that knocks down the visible fire may permit thermal runaway to continue propagating cell-to-cell and reignite once CO₂ concentration falls. The lesson from container-fire investigations is that CO₂ flooding alone is insufficient for lithium-cell fires in cargo holds.
• Foam is not effective on lithium fires beyond cooling (which water alone provides better) and may interfere with subsequent post-fire investigation.
• Dry chemical powder (sodium bicarbonate, monoammonium phosphate) is acceptable for small fires but does not address the underlying cell-to-cell propagation.

The most recent industry guidance from CINS, TT Club and BMP recommends flooding the affected hold with water at the highest practicable rate while activating CO₂ flood as a secondary measure, then monitoring temperature continuously by infrared from outside the affected compartment.

Marine-pollutant spill response

For marine-pollutant spillage at sea, the response is governed by both MARPOL Annex III (which mandates retention of spilled material on board where practicable) and the OPRC Convention’s HNS Protocol (which sets the international response framework for hazardous and noxious substances spills). Containers lost overboard with marine-pollutant content trigger the casualty-reporting obligations under SOLAS Regulation V/31 and Annex III Regulation 7. The vessel’s Garbage Management Plan and Shipboard Oil Pollution Emergency Plan cover related but distinct response regimes.

Elevated-temperature substance fire

A fire involving an elevated-temperature substance presents two parallel hazards: the cargo itself at 100-180°C provides ignition energy to surrounding combustibles, and the structural insulation around the tank or cargo-block may itself burn (mineral wool insulation does not, but the binders and outer cladding sometimes do). The recommended response is exterior cooling of the tank wall with copious water, never internal water injection (which would cause a steam explosion in molten material), and isolation of the heating coils to prevent additional thermal input.

Documentation

MDGF for Class 9

The Multimodal Dangerous Goods Form (MDGF) for Class 9 follows the standard IMDG Code 5.4.1 format with several class-specific data elements:

• For lithium batteries: watt-hour rating per cell and per battery (Li-ion) or lithium content per cell and per battery (Li-metal); section (IA, IB, II); UN 38.3 test report reference; state of charge if declared; whether shipped under packing instruction P903, P911 (damaged/defective) or P909 (waste).
• For marine pollutants: the “MARINE POLLUTANT” annotation appended to the proper shipping name, plus the technical name of the dominant pollutant (in parentheses).
• For elevated-temperature substances: the actual transport temperature in °C, the flash point if applicable, the volume of the consignment.
• For dry ice: the mass of CO₂ in the package and the total package count (because the carrier needs both per-package and aggregate figures to size ventilation in stowage spaces).
• For UN 3268 safety devices: the SP 280 classification approval reference.

Container packing certificate

A signed Container Packing Certificate (sometimes integrated into the MDGF) is required for all containerised Class 9 cargo confirming that the packaging is undamaged, the load is properly secured, segregation within the container is observed, and the marking and labelling are correct.

Carrier acceptance and special declarations

Many carriers require additional documentation for Class 9 lithium-battery shipments beyond the IMDG minimum: a Lithium Battery Test Summary in the form prescribed by Special Provision 188, manufacturer cell-design documentation, and (for damaged or defective cargoes) the competent-authority approval letter in full, not merely a reference. Carriers’ Special Cargo Departments review these documents before booking confirmation.

Notable casualties

Maersk Honam, March 2018

The 15,200 TEU container ship Maersk Honam suffered a catastrophic cargo-hold fire on 6 March 2018 in the Arabian Sea while en route from Singapore to Suez. Five crew members were killed. The vessel was eventually towed to UAE waters; the fire burned for weeks and partial cargo recovery operations extended for months. Total loss exceeded $1.6 billion and the casualty was declared general average, at the time the largest GA in container-ship history. The investigation pointed to mis-declared dangerous goods, including Class 9 entries containing lithium cells alongside Class 4 self-heating materials, in cargo bays forward of the accommodation block. Following Honam, Maersk introduced a 70-point cargo-acceptance reform and prohibited certain combinations of Class 4.2 self-heating cargoes in adjacent stowage. The incident is widely cited as the inflection point for industry recognition of Class 9 cargo risk.

Yantian Express, January 2019

The Yantian Express suffered a container fire mid-Atlantic on 3 January 2019; the fire burned for nearly three weeks before being declared extinguished. Investigation pointed to lithium-ion cell thermal runaway in a deck-stow container as the likely initiation event, with subsequent escalation across multiple bays.

MSC Flaminia, July 2012

The MSC Flaminia explosion and fire on 14 July 2012 (mid-Atlantic) killed three crew members. The primary cause was identified as polymerisation of divinylbenzene (DVB) in IBC tanks within a deck-stow container; the cargo had been mis-classified as Class 3 when it should have been Class 4.1 self-reactive. While the initiation was not Class 9, the casualty contributed to the industry’s understanding of how mis-declared cargo across multiple classes drives container-fire risk, and several Class 9 entries (including marine pollutants and lithium batteries) were among the additional cargoes that contributed to the ultimately catastrophic fire load.

X-Press Pearl, May 2021

The X-Press Pearl was a 2,743 TEU feeder ship that caught fire off Colombo, Sri Lanka on 20 May 2021 and was a complete loss. Investigation identified leakage from a container of nitric acid (Class 8) as the initiation event, but Class 9 cargoes including marine pollutants and lithium batteries contributed to the fire propagation and to the marine-environment damage that followed (substantial release of plastic nurdles from the vessel onto Sri Lankan beaches, an environmental catastrophe in its own right). The incident drove regulatory and industry attention to plastic-pellet packaged cargo as a separate marine-pollutant category, work that is ongoing at IMO MEPC.

Zim Kingston, October 2021

The Zim Kingston lost approximately 109 containers overboard off the British Columbia coast on 22 October 2021 in heavy weather, then suffered a cargo-hold fire in the remaining stow shortly afterwards. The fire involved containers carrying mixed Class 9 cargoes including lithium-cell consignments and self-heating materials. The casualty highlighted the sequential relationship between container loss in heavy weather and fire, packages exposed to seawater incursion and physical damage during stack collapse become substantially more likely to enter thermal runaway.

MV Felicity Ace, February 2022

The pure-car carrier Felicity Ace, carrying about 4,000 vehicles including a substantial number of electric and hybrid vehicles (UN 3171), caught fire in mid-Atlantic on 16 February 2022 and sank with the loss of the ship. The fire’s exact origin was not conclusively identified, but the substantial fuel load from lithium-ion vehicle batteries was cited as a key factor in the fire’s intensity and the inability of fire-fighting parties to control it. The casualty has driven new class-society guidance on EV stowage and fire-detection on PCTC tonnage.

Class 9 in IMDG Code amendments

Class 9 has seen major regulatory development across the IMDG Code amendment cycle. Amendment 36-12 (in force 1 January 2014) introduced Section II for lithium batteries with the small-cell exemption and the lithium-battery handling mark. Amendment 38-16 (in force 1 January 2018) added Special Provision 376 for damaged/defective cells and packing instruction P911. Amendment 39-18 (in force 1 January 2020) further refined lithium-battery rules including state-of-charge guidance for waste batteries. Amendment 40-20 (in force 1 June 2022) introduced UN 3536 (lithium batteries installed in cargo transport units) for transport-unit-mounted battery installations such as battery-electric reefer power systems. Amendment 41-22 (in force 1 January 2024) introduced the new lithium-battery EmS schedule F-H and S-I, and clarified the boundary between damaged/defective batteries and waste batteries.

See also

• International Maritime Dangerous Goods (IMDG) Code overview
• IMDG Class 1 Explosives
• IMDG Class 2 Gases
• IMDG Class 3 Flammable Liquids
• IMDG Class 4 Flammable Solids
• IMDG Class 5 Oxidisers and Organic Peroxides
• IMDG Class 8 Corrosive Substances
• SOLAS Chapter VII Carriage of Dangerous Goods
• MARPOL Annex III Harmful Substances in Packaged Form
• Container Ship
• IMSBC Code
• IMSBC Group A Cargoes

References

• International Maritime Organization. International Maritime Dangerous Goods (IMDG) Code, 2022 edition (Amendment 41-22), Volumes 1 and 2. Chapters 2.9 (Class 9 classification criteria), 2.10 (marine pollutants), 3.2 (Dangerous Goods List), 3.3 (Special Provisions including SP 188, SP 280, SP 376, SP 377), 4.1 (packing instructions including P903, P904, P909, P911), 5.2 (marking and labelling), 5.4 (documentation), 7.1 (stowage categories), 7.2 (segregation matrix), 7.9 (transport of lithium batteries).
• United Nations. Recommendations on the Transport of Dangerous Goods, Model Regulations, 22nd revised edition (the Orange Book). UN Class 9 reference framework on which the IMDG Code is based.
• United Nations. Manual of Tests and Criteria, 8th revised edition. Section 38.3 lithium battery transport tests; Section 28 elevated-temperature substance criteria.
• IMO Resolution MSC.522(106) adopting IMDG Code Amendment 41-22 (May 2022).
• IMO Resolution MSC.477(102) adopting IMDG Code Amendment 40-20.
• IMO Resolution MSC.442(95) adopting IMDG Code Amendment 38-16.
• International Convention for the Prevention of Pollution from Ships, 1973, as modified by the 1978 Protocol (MARPOL), Annex III Regulations for the Prevention of Pollution by Harmful Substances Carried by Sea in Packaged Form.
• International Convention for the Safety of Life at Sea, 1974 (SOLAS), Chapter VII Part A Carriage of Dangerous Goods in Packaged Form, Chapter II-2 Fire Safety (Regulations 19 and 20 governing dangerous goods stowage and fire-fighting).
• International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (STCW), Section A-VI/1-4 dangerous goods training.
• CINS (Cargo Incident Notification System), annual industry reports on container fire causation, with statistical attribution to Class 9 mis-declaration as the leading single cause since 2018.
• TT Club / UK P&I Club / Skuld, series of joint loss-prevention bulletins on lithium-battery cargo risk, container-stuffing best practice and damaged-defective battery handling.
• CTU Code, IMO/ILO/UNECE Code of Practice for Packing of Cargo Transport Units (2014), with Annex 7 specifically addressing dangerous goods including Class 9.
• IATA Lithium Battery Shipping Guidelines and IATA Dangerous Goods Regulations, referenced by the IMDG Code for several lithium-battery specific provisions.
• ICAO Technical Instructions for the Safe Transport of Dangerous Goods by Air, modal counterpart to the IMDG Code; many lithium-battery rules were first developed for air transport and subsequently adopted for sea.
• IACS Recommendation No. 165 on Container Stowage Planning for Cargoes Including Dangerous Goods.
• Lloyd’s Register / DNV / ABS class notations for ships carrying dangerous goods (e.g. DNV “DG-P”, LR “LMC + DG”, ABS “DG”).
• Marine Accident Investigation Branch (UK), Federal Bureau of Maritime Casualty Investigation (Germany), Transport Safety Investigation Bureau (Singapore), published casualty reports for Maersk Honam, MSC Flaminia, Yantian Express and other cited incidents.