SOLAS Chapter VII: Carriage of Dangerous Goods

Background

Scope and structure of Chapter VII

Chapter VII is the SOLAS regulatory shell for the carriage of dangerous goods by sea. It does not itself contain the engineering detail of carriage; instead, it imports four detailed mandatory codes through SOLAS reference, each covering a specific dangerous-goods carriage mode:

• IMDG Code (Part A) for packaged dangerous goods.
• IMSBC Code (Part A-1) for solid bulk dangerous goods (also referenced from Chapter VI Part B).
• IBC Code (Part B) for liquid chemicals in bulk.
• IGC Code (Part C) for liquefied gases in bulk.
• INF Code (Part D) for packaged irradiated nuclear fuel and high-level radioactive waste.

Each code addresses the unique hazard profile of its cargo class with proportionate engineering and operational requirements. The IMDG Code, the largest of the five, runs to thousands of pages across two volumes plus a supplement; the IBC and IGC Codes are dense engineering references; the INF Code is short but consequential.

The chapter interlocks with:

• Chapter II-2 Regulation 19 (carriage of dangerous goods) for fire protection of dangerous-goods cargo spaces.
• Chapter VI Regulation 2 (cargo information) for the shipper’s declaration.
• MARPOL Convention Annex II (noxious liquid substances) and Annex III (harmful substances in packaged form) for environmental dimensions.
• STCW Convention for crew training in dangerous goods handling.

Major amendment history

• 1965-1981: The IMDG Code was first adopted in 1965 as a recommendation, then progressively expanded through the 1970s and 1980s. It was voluntary and not all flag states required compliance.
• 2002 (entered into force 2004): IMDG Code made mandatory through Resolution MSC.122(75), with simultaneous restructuring of Chapter VII to import the code through SOLAS reference. The mandatory transition was driven by the recognition that voluntary application had produced inconsistent compliance across flag states and ports, with ongoing dangerous-goods incidents that the code could have prevented.
• 1971 (IBC) and 1975 (BCH Code precursor): The IBC Code traces its origins to the Bulk Chemical Code adopted in the 1970s as a recommendation. The IBC Code became mandatory in 1986 for ships built after 1 July 1986, with the predecessor BCH Code applying to existing ships.
• 1976 (IGC) and earlier: The IGC Code traces its origins to the Gas Carrier Code adopted in 1976 as a recommendation. The IGC Code became mandatory in 1986 for ships built after 1 July 1986, with the predecessor GC Code applying to existing ships.
• 2014 IGC Code rewrite: A substantial rewrite under Resolution MSC.370(93) updated the IGC Code to reflect modern containment systems, dual-fuel propulsion, and the integration with the IGF Code under Chapter II-1 Part G.
• 1993 INF Code adoption, 1999 mandatory entry: The INF Code addresses the safe carriage of packaged irradiated nuclear fuel, plutonium and high-level radioactive waste. It was adopted in 1993 and made mandatory under SOLAS in 1999.
• Continuous IMDG biennial amendments: The IMDG Code is amended every two years (current cycle: amendment 41-22 in force from 1 January 2024) with new UN entries, updated test methods, and operational improvements.

The dangerous goods regulatory ecosystem

The four codes do not operate in isolation. They are coordinated with:

• UN Recommendations on the Transport of Dangerous Goods (UN Model Regulations): the parent document from which IMDG, IATA Dangerous Goods Regulations (air), ADR (European road) and RID (rail) are derived. The UN classification system (Class 1 to Class 9 with packing groups, UN numbers, proper shipping names) is consistent across all transport modes.
• MARPOL Annex III: the marine pollutant designation aligned with IMDG marine pollutant flagging.
• Hazardous and Noxious Substances (HNS) Convention: the liability and compensation regime for HNS spills (not yet in force globally as of 2026).
• ISPS Code (Chapter XI-2): security implications of dangerous goods cargo.

Part A: Carriage of dangerous goods in packaged form (IMDG Code)

Scope of the IMDG Code

The IMDG Code governs the carriage of dangerous goods in packaged form on ships subject to SOLAS. Packaged form includes:

• Drums, jerricans, bags, boxes, and other primary packaging containing the dangerous substance.
• Intermediate Bulk Containers (IBCs) of various types (rigid, flexible, composite) holding up to 3,000 litres or 3,000 kg.
• Tank containers (T-codes T1 to T75) for liquid and gas dangerous goods at intermediate scale.
• Portable tanks for cryogenic or pressurised cargo.
• Containers (general-purpose and tank containers) used for consolidated dangerous-goods shipments.

The IMDG Code does not apply to:

• Bulk dangerous goods (solid bulk: IMSBC; liquid chemical bulk: IBC; gas bulk: IGC).
• Dangerous goods carried as ship’s stores (fuel, lubricants, paints) which are governed by the relevant SOLAS chapters and MARPOL Annexes.
• Quantities below the excepted quantity thresholds, which are exempt from full IMDG requirements.
• Limited quantities (small consumer-pack sizes) which have abbreviated requirements.

IMDG Code structure

The IMDG Code is structured into seven Parts:

• Part 1: General provisions, definitions and training.
• Part 2: Classification (the UN Class system: Class 1 explosives, Class 2 gases, Class 3 flammable liquids, Class 4 flammable solids and self-reactive substances, Class 5 oxidising substances and organic peroxides, Class 6 toxic and infectious substances, Class 7 radioactive material, Class 8 corrosive substances, Class 9 miscellaneous dangerous goods including marine pollutants).
• Part 3: Dangerous Goods List, Special Provisions and Exceptions: the alphabetical and numerical listing of UN-numbered substances with their classifications, packing groups, packing instructions, EmS references, MFAG references, stowage and segregation requirements.
• Part 4: Packing and tank provisions: the detailed packaging requirements by UN entry.
• Part 5: Consignment procedures: marking, labelling, placarding, documentation, training certificates.
• Part 6: Construction and testing of packagings, IBCs, large packagings, portable tanks, multi-element gas containers, road tank vehicles and bulk containers.
• Part 7: Provisions concerning transport operations: stowage, segregation, fumigation, security, additional requirements for certain types of cargo, classification societies and competent authorities.

The Code is supplemented by:

• The EmS Guide (Emergency Response Procedures for Ships Carrying Dangerous Goods): emergency response schedules referenced by EmS code in the Dangerous Goods List.
• The MFAG (Medical First Aid Guide for Use in Accidents Involving Dangerous Goods): medical first-aid guidance for crew exposed to dangerous goods.
• The CTU Code (Code of Practice for Packing of Cargo Transport Units): the loading guidance for containers.

Document of Compliance for the carriage of dangerous goods

Every ship intending to carry IMDG-regulated dangerous goods must hold a Document of Compliance for the Carriage of Dangerous Goods (DoC) issued by the flag state. The DoC:

• Lists the IMDG classes the ship is approved to carry.
• Records the segregation arrangements between cargo holds (e.g. which holds can carry Class 1 simultaneously with Class 5).
• Specifies any exclusions for specific UN entries.
• Is checked at PSC inspections against the actual cargo manifest.

The Reg VII/3 DG carriage calculator returns the DoC content for a given ship.

IMDG class deep dives

ShipCalculators.com has dedicated wiki articles for each IMDG class:

• IMDG Class 1 Explosives, divisions 1.1 to 1.6 by mass-explosion characteristic, compatibility groups A to S.
• IMDG Class 2 Gases, division 2.1 flammable gases, 2.2 non-flammable non-toxic, 2.3 toxic.
• IMDG Class 3 Flammable Liquids, packing groups by flash point and initial boiling point.
• IMDG Class 4 Flammable Solids, divisions 4.1 flammable solids, 4.2 spontaneously combustible, 4.3 water-reactive.
• IMDG Class 5 Oxidisers and Organic Peroxides, division 5.1 oxidisers, 5.2 organic peroxides with SADT temperature control.
• IMDG Class 8 Corrosive Substances, packing groups by skin destruction time and corrosion rate on steel.

Class 6 (toxic and infectious substances), Class 7 (radioactive material) and Class 9 (miscellaneous dangerous goods) are addressed in the Chapter VII article through their interaction with the relevant IMDG Code sections.

Multimodal Dangerous Goods Form and shipper declaration

For each consignment of dangerous goods, the shipper must complete a Multimodal Dangerous Goods Form (or equivalent shipper’s declaration) including:

• UN number and proper shipping name.
• Class and (where applicable) division and compatibility group.
• Packing group.
• Packaging type and certification mark.
• Quantity (mass or volume).
• Number and type of packages.
• Marine pollutant designation (under MARPOL Annex III).
• EmS code reference.
• Special provisions reference.
• Container/vehicle identification.
• Shipper and consignee details.
• Emergency contact information.

The form is signed by the shipper and accompanies the cargo as a regulatory and operational document. Mis-declaration is an offence in flag-state and port-state law.

Container Packing Certificate

For containerised dangerous goods, the shipper or packer issues a Container Packing Certificate confirming that the container has been packed in accordance with the IMDG Code Part 7 (stowage and segregation within the container, blocking and bracing, placard application, documentation accompaniment).

The post-incident pattern of container ship fires (Maersk Honam 2018, X-Press Pearl 2021) has driven industry-led initiatives to verify these certificates through random inspection (NCB, terminal inspections, random verification programmes by major carriers).

Marking, labelling and placarding

Dangerous goods packages must be marked with:

• UN number with the prefix “UN” (e.g. UN 1230 for methanol).
• Proper shipping name.
• Class label(s) in the prescribed shape, colour and symbol.
• Marine pollutant mark (where applicable).
• Orientation arrows for liquids in non-vertical packagings.
• Limited quantity mark (where applicable).

Containers and other cargo transport units carrying dangerous goods must be placarded on each long side and each short side with:

• The class placard for each class carried.
• The UN number panel for the largest UN number carried (or for each UN number for tank containers).
• Marine pollutant placard where applicable.

EmS schedules and MFAG

The IMDG Code’s emergency response is coordinated through:

• EmS schedules: numbered fire schedules (F-A, F-B, …, F-J) and spillage schedules (S-A, S-B, …, S-Z) prescribing the response action for fire or spillage of cargoes in each schedule. Each UN entry in the Dangerous Goods List references one fire and one spillage schedule.
• MFAG: medical first-aid guidance for crew exposed to dangerous goods, with specific antidotes, treatment protocols and evacuation criteria.

The IMDG EmS lookup returns the EmS reference for any UN entry.

Segregation rules

The IMDG Code Chapter 7 sets out segregation rules between dangerous goods classes and between dangerous goods and foodstuffs. The segregation table specifies a numerical level (1 to 4) for each class-versus-class combination, with each level corresponding to a minimum physical separation:

• Segregation 1 (“Away from”): stowed in different stowage location, no minimum distance.
• Segregation 2 (“Separated from”): separated by an effective distance.
• Segregation 3 (“Separated by a complete compartment or hold”): separated by a watertight bulkhead or deck.
• Segregation 4 (“Separated longitudinally by an intervening complete compartment or hold”): maximum separation, used for incompatibilities that produce serious reactions on contact.

The IMDG segregation calculator computes the required segregation between any pair of UN entries.

Part A-1: Carriage of dangerous goods in solid form in bulk (IMSBC Code)

Part A-1 imports the IMSBC Code (already covered in Chapter VI Part B) for solid bulk cargoes carried under dangerous-goods classifications. The cross-reference avoids duplicating the IMSBC requirements between Chapters VI and VII while keeping the dangerous-goods regulatory framework coherent.

The principal solid bulk dangerous goods are Group B cargoes under the IMSBC: coal (CO emission, oxygen depletion, self-heating), direct reduced iron (hydrogen emission and self-heating), sulphide ores (SO2 and H2S emission), fishmeal (CO emission and self-heating), various mineral concentrates with chemical hazards.

The IMSBC Code article and the IMSBC Group A cargoes article cover the detail.

Part B: Construction and equipment of ships carrying dangerous liquid chemicals in bulk (IBC Code)

Scope of the IBC Code

The IBC Code (International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk, Resolution MSC.4(48)) governs the construction, equipment and operation of chemical tankers: ships designed and used for the bulk carriage of any dangerous chemicals listed in Chapter 17 of the IBC Code (the IBC Code’s Cargo Lists).

The IBC Code applies to chemical tankers built after 1 July 1986. Earlier-built ships are governed by the BCH Code (Bulk Chemical Code, the predecessor to IBC, with similar but less stringent requirements).

Ship type classifications

The IBC Code classifies chemical tankers into three types based on the cargoes they are designed to carry:

• Type 1: ships intended to transport products with very severe environmental and safety hazards. Survival of damage is the highest priority. Hold construction provides maximum survivability.
• Type 2: ships intended to transport products with appreciable environmental and safety hazards. Significant preventive measures are needed.
• Type 3: ships intended to transport products with sufficiently severe environmental and safety hazards to require a moderate degree of containment to increase survival capability in damaged conditions.

The Cargo List specifies which cargoes can be carried on each ship type.

Cargo containment and structural requirements

Specific IBC requirements include:

• Cargo tank arrangement with double bottom and double hull (depending on ship type), providing barrier against collision and grounding damage.
• Tank materials compatible with the cargo: stainless steel, special coatings, certain other materials approved per the Cargo List.
• Independent piping systems for incompatible cargoes (acid versus base, oxidiser versus reductant, water-reactive versus aqueous).
• Cargo tank ventilation with vapour control to prevent atmospheric release of vapours and to maintain inert atmosphere where required.
• Cargo handling pumps of approved type for the cargo, with material compatibility and explosion-proof certification where flammable cargoes are carried.
• Tank cleaning systems for changeover between cargoes (Crude Oil Washing for similar oils, fresh-water rinse for some cargoes, chemical cleaning for residue removal).

Fire protection and safety systems

IBC ships have additional fire protection beyond standard SOLAS Chapter II-2:

• Deck foam system capable of covering the cargo deck with foam in case of cargo fire.
• Inert gas system maintaining cargo tank ullage atmosphere below the lower flammable limit (oxygen below 8 percent for hydrocarbon cargoes).
• Water-spray system for cooling adjacent structure during fire.
• Pumproom safety: the cargo pumproom is a hazardous area requiring continuous gas detection, certified electrical equipment, mechanical ventilation, escape route segregation.
• Cargo emergency shutdown system permitting immediate cargo flow termination by remote control from multiple locations.

Personnel protection

IBC ships carry:

• Self-contained breathing apparatus (SCBA) for tank entry and emergency response.
• Decontamination shower and eyewash station near cargo handling areas.
• Chemical-resistant suits for handling specific cargo types.
• Antidote kits for cargoes with established medical first aid (e.g. cyanide antidote for cargoes that release HCN on contact with acid).

MARPOL Annex II linkage

The IBC Code is closely linked to MARPOL Annex II (Noxious Liquid Substances). Annex II classifies cargoes into four categories (X, Y, Z, OS for Other Substances) by environmental hazard. Discharge of cargo residues to the marine environment is prohibited or restricted depending on the category. The IBC Code Cargo List is the primary reference for both safety (IBC) and environmental (Annex II) requirements.

Part C: Construction and equipment of ships carrying liquefied gases in bulk (IGC Code)

Scope of the IGC Code

The IGC Code (International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk, Resolution MSC.5(48), as updated by MSC.370(93) in 2014) governs the construction, equipment and operation of gas carriers: ships designed for the bulk carriage of liquefied gases listed in IGC Code Chapter 19.

The IGC Code applies to gas carriers built after 1 July 1986; earlier ships are governed by the GC Code (Gas Carrier Code, predecessor to IGC).

The principal cargoes are:

• LNG (Liquefied Natural Gas): methane at minus 162 degrees Celsius. The largest tonnage of gas-carrier traffic.
• LPG (Liquefied Petroleum Gas): propane and butane at moderate refrigeration or pressure.
• Ethylene: ethylene at minus 104 degrees Celsius.
• Ammonia: anhydrous ammonia at minus 33 degrees Celsius or under pressure.
• Other gases: butadiene, propylene, vinyl chloride monomer, ethylene oxide, etc.

Containment systems

Gas carriers use specialised cargo containment systems:

• Membrane containment (LNG): thin metallic membrane lining the cargo hold, supported by insulation. Two principal designs: Mark III (GTT) and NO 96 (GTT). Membrane systems are space-efficient and used on the largest LNG carriers.
• Moss spherical containment (LNG): independent spherical aluminium tanks within the hull, exposed above deck. Used on a significant fraction of older LNG carriers.
• Type A independent tanks (LPG): prismatic cargo tanks with internal stiffeners, full secondary barrier required.
• Type B independent tanks (LNG, LPG, ethylene): stress-engineered tanks with partial secondary barrier permitted.
• Type C independent tanks (LPG, ethylene, smaller LNG): pressure-vessel-style tanks with inherent strength.

The choice of containment depends on cargo properties, design pressure, design temperature and operational economics.

Cargo handling systems

IGC ships have specialised cargo handling:

• Cargo pumps of submerged type (for LNG) or deck-mounted type (for LPG), with cryogenic-rated materials and seals.
• Pipework of cryogenic stainless steel or aluminium for LNG; carbon steel or alloy steel for LPG depending on temperature.
• Vapour return for cargo tank pressure control during loading and discharging.
• Inert gas system supplying nitrogen or generated inert gas for tank purging during cargo changeover.
• Boil-off gas (BOG) management for LNG: BOG can be re-liquefied, used as fuel in the main propulsion (dual-fuel diesel-electric, steam-turbine, or DFDE), flared, or held in cargo tanks at pressure.

Hazardous-area management

IGC ships have extensive hazardous-area zoning:

• Zone 0 (continuous flammable atmosphere): inside cargo tanks and immediate vicinity.
• Zone 1 (flammable atmosphere likely): cargo deck during operations, vent posts during venting.
• Zone 2 (flammable atmosphere unlikely except in fault conditions): broader cargo deck area, certain pump room areas.

Electrical equipment in each zone must be of appropriate explosion-protection certification.

Fire protection

IGC ships have:

• Water spray system covering the cargo deck.
• Dry chemical powder fire extinguishers at strategic deck locations.
• Fixed CO2 or inert gas system for protected machinery spaces.
• Cargo deck access restricted during cargo operations.

LNG carrier link

The LNG carrier article provides further detail on LNG-specific operations, the global LNG fleet, the dual-fuel propulsion options, and the connection to LNG as marine fuel under the IGF Code.

Part D: Carriage of packaged irradiated nuclear fuel and high-level radioactive waste (INF Code)

Scope of the INF Code

The INF Code (International Code for the Safe Carriage of Packaged Irradiated Nuclear Fuel, Plutonium and High-Level Radioactive Wastes on board Ships, Resolution MSC.88(71)) governs the carriage of:

• Irradiated nuclear fuel (spent nuclear fuel from power reactors, in transit to reprocessing or storage facilities).
• Plutonium in various forms (oxide, nitrate solution, mixed oxide fuel).
• High-level radioactive waste (vitrified waste from reprocessing, transuranic waste, certain reactor decommissioning waste).

The INF Code applies to ships of any size carrying these materials in packaged form.

INF ship categories

The INF Code classifies ships into three categories based on the radioactivity inventory carried:

• INF 1: ships certified to carry packages with total radioactivity below 4,000 TBq. Standard SOLAS construction with INF Code additions.
• INF 2: ships certified to carry packages with total radioactivity above 4,000 TBq and below 2,000,000 TBq for irradiated fuel (or 2,000 TBq for high-level waste). Strengthened structure, fire protection and stability requirements.
• INF 3: ships certified to carry packages with total radioactivity above 2,000,000 TBq for irradiated fuel (or 2,000 TBq for high-level waste). Highest construction standards, with damage-stability requirements equivalent to or exceeding tanker requirements.

Specific INF requirements

INF ships have requirements proportional to category:

• Hull strength: progressively higher for INF 2 and INF 3 to withstand collision impact and grounding damage with no breach of cargo containment.
• Damage stability: passive survival of multi-compartment damage scenarios.
• Fire protection: cargo space fire protection significantly enhanced beyond standard SOLAS, with monitoring of cargo package integrity.
• Cargo containment: secondary containment around cargo packages, with monitoring for leakage.
• Crew radiation protection: monitored radiation exposure with health surveillance, dosimeters, and procedures for handling radioactive cargo.
• Emergency response: dedicated radiation emergency procedures, communication with national radiation safety authorities.

Routes and ports

INF cargo is shipped on a small number of dedicated routes (UK to Japan via Cape of Good Hope or Panama Canal; UK or France to USA via the Atlantic). Ports along the route have specific arrangements for INF transit, with notification, escort and emergency response coordination.

Notable casualties and incidents

Container ship fires from mis-declared dangerous goods

The container ship fires of the past decade illustrate the operational consequences of failures in Chapter VII compliance:

• Maersk Honam, 2018 (5 dead): cargo hold fire involving Class 5.1 calcium hypochlorite, contributing to industry-led pre-stowage segregation initiatives.
• MSC Flaminia, 2012 (3 dead): fire during voyage involving Class 5.1 organic peroxide that had been mis-declared.
• Hyundai Fortune, 2006: fire after explosion attributed to mis-declared cargo.
• Hanjin Pennsylvania, 2002: fire and abandonment, mis-declared cargo as a contributor.
• X-Press Pearl, 2021: nitric acid container leak ignited combustibles, severe environmental damage.

These incidents share a common pattern: dangerous goods declared incorrectly (wrong class, wrong quantity, wrong UN number, or undeclared), allowing the cargo to be stowed without the segregation that would have prevented fire spread.

The CINS (Cargo Incident Notification System) industry database tracks these incidents at scale and is used by carriers to identify mis-declaration patterns.

Chemical tanker incidents

The IBC Code’s safety record is generally strong, but incidents include:

• Bow Mariner, 2004 (21 dead): explosion during tank cleaning of methyl tertiary butyl ether (MTBE) residue. Drove tightening of inert-gas requirements and tank-cleaning procedures.
• Stolt Valor, 2012 (1 dead): explosion in cargo tank during tank cleaning. Drove tightening of operator training under STCW Section A-V/1 (chemical tanker familiarisation).

LNG carrier incidents

LNG carriers have an exceptional safety record across the global fleet, with no LNG-fire-related fatalities at sea in the cargo industry’s history. Operational incidents include:

• Norman Lady, 1979: containment damage during loading, no cargo release.
• Tenaga Lima, 1976: minor cargo leak during transit, contained.
• Various LNG carrier groundings without containment breach, demonstrating the strength of the IGC Code’s structural requirements.

The strong safety record reflects the conservative engineering of the IGC Code, the highly trained crews under STCW Section A-V/1 (gas carrier familiarisation), and the operational discipline of the LNG industry.

INF transit incidents

INF transits have not produced cargo release casualties, with the INF Code’s structural and operational requirements providing substantial safety margins. Public concerns about INF transits (especially through the English Channel and through south-east Asian waters) have driven enhanced port-state notification requirements but have not been borne out by actual casualties.

Chemical tanker operations under IBC Code

Cargo loading and discharge

Chemical tanker cargo operations require coordinated procedures across multiple checkpoints:

• Pre-arrival checks: confirm cargo compatibility with previous cargo (residue, tank coating, materials of construction); verify availability of cargo handling equipment; review the Cargo Information Form provided by the shipper.
• Mooring and connection: secure mooring with sufficient redundancy for the cargo grade; connect cargo loading arms or hoses with verified compatibility for cargo temperature and pressure.
• Pre-loading checklist (Ship-Shore Safety Checklist): completed jointly with the terminal, covering communication arrangements, emergency response, weather conditions, vapour return arrangements, fire-fighting readiness, electrical isolation.
• Loading: cargo flows at controlled rate (typically 200 to 1000 cubic metres per hour for chemical cargoes), with continuous monitoring of cargo tank level, temperature, pressure, oxygen content and toxic gas concentration (where applicable).
• Topping off: final loading at reduced rate to fill cargo tanks to the design ullage.
• Departure: tank closure verification, cargo securing, mooring release, harbour clearance.

The procedures are documented in the Tanker Safety Guide (ICS publication) and operationalised through the ISM Code Safety Management System.

Tank cleaning between cargoes

Chemical tankers frequently change cargo grades between voyages, requiring tank cleaning to a specified residue level. The cleaning procedure varies by cargo:

• Hydrocarbon-to-hydrocarbon: typically simple sea water washing or fresh water rinse.
• Hydrocarbon-to-aqueous: more rigorous cleaning to remove all residual hydrocarbon below acceptance threshold.
• Aqueous-to-hydrocarbon: drying and inspection to remove all moisture.
• Acid-to-base: chemical neutralisation followed by water rinse.
• High-purity cargoes: chemical cleaning with specific solvents to remove residue at sub-ppm level.

Tank cleaning is hazardous: it involves entry into confined spaces, potential exposure to residual chemical vapours, and risk of static-electric ignition where flammable atmospheres are possible. The Bow Mariner casualty (2004, 21 dead) involved an explosion during MTBE residue cleaning and drove tightening of inert-gas requirements during chemical tanker tank cleaning.

Pump room safety

The cargo pump room on a chemical tanker is one of the highest-risk spaces on board:

• Hazardous area Zone 1: flammable atmosphere likely during cargo operations.
• Continuous gas detection for hydrocarbon vapour and (where relevant) toxic gas.
• Mechanical ventilation with air-flow rate sufficient to dilute leakage below LEL.
• Certified explosion-protected electrical equipment.
• Independent fire detection and alarm.
• Two means of escape to upper deck via gas-tight access trunks.
• Pre-entry gas check by hand-held detector before each entry.
• Two-person rule: no solo entry to the pump room during cargo operations.

The IBC Code Chapter 3 specifies the pump room arrangement and operational requirements.

Gas carrier operations under IGC Code

LNG carrier operations

LNG carriers operate on long-haul trades (typically 10 to 25 day voyages) between liquefaction terminals and regasification terminals. Operational features include:

• Cargo containment at minus 162 degrees Celsius requires continuous insulation maintenance and boil-off gas (BOG) management.
• BOG fuel use: most modern LNG carriers (DFDE, ME-GI, X-DF) use BOG as fuel in the main propulsion, capturing the otherwise-vented gas.
• Cargo cool-down at the start of each new contract requires controlled chilling of the cargo containment to avoid thermal stress.
• Cargo warm-up at end-of-contract requires controlled warming, typically requiring multiple days at port.
• Reliquefaction on some modern LNG carriers permits BOG to be reliquefied and returned to the cargo tanks rather than used as fuel.

The LNG cargo industry has an exceptional safety record: no fatal LNG fires in the cargo industry’s 60+ year history at sea. The conservative engineering of the IGC Code, the highly trained crews under STCW Section A-V/1, and the operational discipline of the LNG industry collectively account for this record.

Other gas carrier operations

LPG carriers, ethylene carriers and ammonia carriers operate similar but smaller-scale operations with different cargo properties. Common operational issues include:

• Cargo contamination: cross-contamination between cargo grades is a significant cargo claim risk.
• Pressure containment: pressure-rated tanks require integrity verification at each loading.
• Toxic exposure (ammonia): ammonia carriers carry specific personal protective equipment and decontamination provisions for the toxicity hazard.

INF Code routes and shipments

Active INF routes

Specific INF transit routes have been used since the 1990s:

• UK to Japan: spent fuel reprocessing at Sellafield (UK), reprocessed plutonium and high-level waste returns to Japanese utilities. Routes via Cape of Good Hope or Panama Canal.
• France to Japan: similar reprocessing trade, La Hague (France).
• France to USA: occasional shipments for research reactor fuel.
• UK and France to Russia: limited shipments for research and reprocessing.

Each route requires:

• Flag-state notification to the IMO and to each transit state’s competent authority.
• Coastal state notification for transits within EEZs (some states have additional sovereign-rights notifications).
• Route security assessment with avoidance of specific high-risk areas.
• Naval or coast guard escort for parts of the route through congested or politically sensitive waters.

INF ship operators

A small number of operators (PNTL Pacific Nuclear Transport Limited, formerly BNFL/BNFLI; INS International Nuclear Services; certain Russian and French specialised carriers) operate dedicated INF ships. The fleet is small (under 10 ships globally) but each ship has lifetime operational planning around the INF trade.

INF Code amendments

The INF Code has been amended several times since 1999 to reflect evolving radioactive waste management practices and post-Fukushima (2011) considerations. Specific amendments addressed:

• Mixed oxide fuel (MOX) containers and packages.
• Vitrified waste (HLW) package specifications.
• Spent fuel cooling time requirements before transit.
• Radiation exposure limits for crew and dose monitoring procedures.

Specific cargo handling considerations by class

Class 1 explosives operational considerations

Class 1 explosives require additional precautions beyond standard IMDG provisions:

• Compatibility groups: Class 1 entries are sub-classified by compatibility group (A through S), governing which entries can be stowed adjacent to each other. The IMDG Class 1 segregation table is more restrictive than the general IMDG segregation table.
• Quantity limits: maximum quantities of certain Class 1 entries per cargo space depending on division (1.1 mass-explosion-risk has the strictest limits).
• Stowage requirement: typically Category D (on-deck only or in dedicated below-deck magazines with fire-resistant separation).
• Lockable storage for high-security items (military explosives, certain commercial blasting agents).

Class 2 gases operational considerations

Class 2 gases require:

• Stowage clear of accommodation for division 2.1 (flammable) and 2.3 (toxic).
• Ventilation of the cargo space for atmospheric gas accumulation.
• Pressure relief on pressure-rated containers, with relief discharge pointed away from accommodation and ignition sources.
• Toxic gas detection in cargo spaces carrying division 2.3 entries.

Class 3 flammable liquids operational considerations

Class 3 flammable liquids require:

• Segregation from oxidisers and from incompatible chemicals.
• No hot work in the vicinity of stowed Class 3 cargo.
• Emergency response preparation including foam supply, water spray and cooling capacity.
• MARPOL Annex III marine pollutant designation for many Class 3 entries.

Class 4 flammable solids operational considerations

Class 4 flammable solids include three sub-classes with different operational requirements:

• Division 4.1 (flammable solids): stowage clear of ignition sources.
• Division 4.2 (spontaneously combustible): temperature monitoring during voyage.
• Division 4.3 (water-reactive): absolutely dry stowage; no contact with water or moist atmosphere.

Class 5 oxidisers and organic peroxides operational considerations

Class 5 requires:

• Strict segregation from combustibles and from acids.
• Temperature control for division 5.2 organic peroxides (continuous refrigeration during voyage).
• No hot work in vicinity of Class 5 stowage.

Class 6 toxic and infectious substances operational considerations

Class 6 covers two distinct hazard streams: division 6.1 toxic substances (cyanide compounds, arsenic compounds, mercury compounds, organophosphate and carbamate pesticides, methyl bromide fumigant, chloroform, methanol at toxic concentration, aniline, nicotine and many industrial intermediates) and division 6.2 infectious substances (UN 2814 Category A human pathogens, UN 2900 Category A animal pathogens, UN 3373 Category B diagnostic specimens, UN 3291 clinical waste). The two divisions share the regulatory chapter but have very different operational profiles: Class 6.1 is shipped in large volumes through general containerised freight, while Class 6.2 is shipped in much smaller volumes through dedicated medical-courier networks. Both require strict separation from foodstuffs and segregation from incompatible chemicals (especially acids that release HCN with cyanide entries).

Class 7 radioactive material operational considerations

Class 7 radioactive material in IMDG-coded form (transport indices, radiation indices, criticality safety indices) requires shielded packaging certified to UN type tests, surface-radiation-level marking, transport documents matching the IAEA Regulations for the Safe Transport of Radioactive Material, and specific stowage categories that limit deck radiation exposure. The bulk of radioactive material movements are in low-radiation forms (medical isotopes, industrial radiography sources, low-level waste) that are within Class 7 but not subject to the INF Code Part D requirements.

Class 9 miscellaneous dangerous goods operational considerations

Class 9 covers a heterogeneous list including marine pollutants under MARPOL Annex III, magnetic materials affecting compass operation, environmentally hazardous substances, lithium-ion batteries (UN 3480 and UN 3481 with recent special provisions for damage and thermal runaway), genetically modified organisms, dry ice as a refrigerant for biological cargoes, polymerising substances, and high-temperature materials. Each Class 9 entry has cargo-specific stowage and segregation requirements set out in the IMDG Code Dangerous Goods List.

Class 8 corrosives operational considerations

Class 8 requires:

• Segregation from foodstuffs (the strictest segregation rule in the IMDG Code).
• Acid-base separation to prevent reactive incidents.
• Crew PPE for cargo space entry (chemical-resistant suits, SCBA).
• Damage detection to identify leaking containers before they cause structural corrosion.

Container ship dangerous goods stowage planning

Modern container ships carrying dangerous goods operate under stowage planning processes that integrate IMDG Code requirements with the loading computer:

• Pre-stowage analysis: each declared dangerous goods consignment is checked against the IMDG Code segregation table and against the ship’s certificate of compliance for the carriage of dangerous goods. Incompatible cargo combinations are flagged before loading.
• Stowage location assignment: dangerous goods are typically assigned to specific deck or hold positions consistent with segregation requirements, ventilation availability, fire detection coverage, and proximity to accommodation.
• Damaged stowage allocation: containers identified as damaged or with package leakage during loading are reassigned to monitored positions or refused.
• Pre-departure verification: the actual stowage is checked against the planned stowage and the IMDG Code, with the master signing off.

The largest container carriers integrate the IMDG analysis with their main stowage planning systems (Navis, Bluebox, CompuStow), with automatic alerts when planned stowage violates segregation. Despite the automation, mis-declaration by shippers remains the principal residual risk: even a perfect stowage planning system cannot detect mis-declared cargo.

Industry initiatives on dangerous goods compliance

The recurring container ship fire pattern has driven a series of industry-led initiatives operating alongside the regulatory cycle:

• CINS (Cargo Incident Notification System): industry database of container incidents (loss, damage, fire, mis-declaration), shared among carriers and used to identify patterns. Founded by the world’s major container lines.
• National Cargo Bureau (NCB) and similar inspection services: pre-loading random inspection of containers for compliance with IMDG declarations. NCB inspectors have authority to refuse cargo found to be mis-declared.
• IUMI (International Union of Marine Insurance) working group on container ship fires, providing actuarial analysis and risk-based recommendations to insurers and to the IMO.
• Cargo declaration verification programmes by major carriers: Maersk, MSC, CMA CGM, Hapag-Lloyd, ONE and Evergreen all operate cargo verification programmes with random sampling and declared-versus-actual content checks.
• Stowage planning tools with built-in IMDG segregation and dangerous-goods exclusion zones (the post-Honam initiative to keep dangerous goods away from accommodation and from container fire-fighting blind spots).
• Insurance pricing differentials by P&I clubs reflecting the operator’s record on dangerous goods compliance.

Crew training under STCW

Crew on ships carrying dangerous goods require certification under STCW:

• STCW Section A-V/1 paragraph 1: Familiarisation training on tankers (covering oil tankers, chemical tankers, gas carriers) for ratings.
• STCW Section A-V/1 paragraph 2: Advanced training in oil tanker operations for officers in charge of cargo operations on oil tankers.
• STCW Section A-V/1 paragraph 3: Advanced training in chemical tanker operations for officers in charge of cargo operations on chemical tankers (covering IBC Code requirements, cargo properties, tank cleaning).
• STCW Section A-V/1 paragraph 4: Advanced training in liquefied gas tanker operations for officers in charge of cargo operations on gas carriers (covering IGC Code requirements, cryogenic operations, BOG management).
• STCW Section A-V/3: Training for crew on ships subject to the IGF Code (low-flashpoint fuels: LNG, methanol, ethanol; with extension under development for ammonia and hydrogen).
• IMDG Code training (general): required for crew handling dangerous goods on container ships, ro-ro ships and general cargo ships, with content covering classification, packaging, marking, segregation, EmS schedules and emergency response.

The certificates have specified validity (typically 5 years) with refresher training required for renewal.

Port state control

Port state control inspections target dangerous goods carriage with particular intensity due to the casualty record. Common deficiencies include:

• Document of Compliance for the Carriage of Dangerous Goods (DoC): missing, expired, or not aligned with the actual cargo manifest.
• Cargo information: shipper’s declaration not matching the actual cargo or containing inconsistencies.
• Stowage and segregation: actual stowage not matching the IMDG Code requirements or the ship’s certificate.
• Marking and placarding: containers without correct placards or with placards missing required information.
• Emergency equipment: insufficient firefighter outfits, expired EmS equipment, missing antidote kits.
• Crew training: STCW certificates expired, training records incomplete.
• Code copies: missing or out-of-date IMDG, IBC, IGC or INF Code copies on board.

A serious deficiency in dangerous goods carriage can result in detention until rectified. Detention is recorded against the operator’s PSC profile, affecting future inspection priority and inspection intensity.

HNS Convention

The International Convention on Liability and Compensation for Damage in connection with the Carriage of Hazardous and Noxious Substances by Sea (HNS Convention) is a parallel liability and compensation regime for HNS spills, complementing the existing CLC Convention (oil) and Bunker Convention (bunker oil). The HNS Convention covers:

• Bulk HNS (chemical tanker, gas carrier cargoes).
• Packaged HNS (IMDG-coded cargoes with marine pollutant designation).
• Solid bulk HNS (IMSBC Group B chemical-hazard cargoes).

The Convention provides:

• First-tier liability of the shipowner up to specified limits (in SDR).
• Second-tier compensation from a HNS Fund financed by HNS receivers in member states.

The Convention was adopted in 1996 but did not enter into force due to slow ratification. The 2010 Protocol updated the Convention; ratification continues toward entry into force. As of 2026, the Convention has not yet entered into force globally.

Documentation

Every ship covered by Chapter VII carries on board:

• The Cargo Ship Safety Construction Certificate, with evidence of compliance with Chapter VII.
• The Document of Compliance for the Carriage of Dangerous Goods (under Part A).
• The Certificate of Fitness for the Carriage of Dangerous Chemicals in Bulk (chemical tankers under Part B / IBC Code).
• The Certificate of Fitness for the Carriage of Liquefied Gases in Bulk (gas carriers under Part C / IGC Code).
• The INF Certificate (INF ships under Part D / INF Code).
• The IMDG Code copy on board (current amendment).
• The IBC Code copy on board (chemical tankers).
• The IGC Code copy on board (gas carriers).
• The INF Code copy on board (INF ships).
• The EmS Guide and MFAG.
• The shipper’s declarations for dangerous goods consignments.
• The container packing certificates.
• The Cargo Securing Manual (if dangerous goods are containerised).
• Crew dangerous-goods training records under STCW.

Related Calculators

• SOLAS VII/3, Carriage of dangerous goods Calculator
• IMDG Segregation Distance Calculator
• IMDG Packing Group (PG I/II/III) Calculator
• IMDG EmS, Emergency Schedule Calculator
• IMDG Limited Quantity, Mark Check Calculator
• IMDG, Container Hazard Class Display Calculator
• Tank Container, T-Code Selection Calculator
• Imo Imdg Calculator

See also

• SOLAS Convention parent article
• SOLAS Chapter II-1: Construction, Subdivision, Stability, Machinery and Electrical Installations
• SOLAS Chapter II-2: Fire Protection, Detection and Extinction
• SOLAS Chapter VI: Carriage of Cargoes and Oil Fuels
• 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
• IMSBC Code
• IMSBC Group A Cargoes
• Chemical Tanker
• LNG Carrier
• LNG as Marine Fuel
• Methanol as Marine Fuel
• Ammonia as Marine Fuel
• MARPOL Convention
• STCW Convention

Additional calculators:

• ClassNK GF (Gas-Fuelled) Notation
• MARPOL Annex II - NLS Discharge Compliance
• LNG Tank - Secondary Barrier Requirement
• CII Attained Calculator (MEPC.336(76))

Additional formula references:

• Container Imdg Class
• Imdg Class 7 Radioactive
• Imdg Limited Quantity
• Tanker Gas Free Certificate

Additional related wiki articles:

• IGC Code: Construction of Gas Carriers
• MARPOL Annex III: Harmful Substances in Packaged Form

References

• IMO, International Convention for the Safety of Life at Sea (SOLAS), 1974, as amended, Chapter VII.
• IMO, International Maritime Dangerous Goods Code (IMDG Code), Resolution MSC.122(75), 2002, as amended (current Amendment 41-22 from 1 January 2024).
• IMO, International Bulk Chemical Code (IBC Code), Resolution MSC.4(48), 1983, as amended.
• IMO, International Gas Carrier Code (IGC Code), Resolution MSC.5(48), 1983, as updated by Resolution MSC.370(93), 2014.
• IMO, International Code for the Safe Carriage of Packaged Irradiated Nuclear Fuel, Plutonium and High-Level Radioactive Wastes on board Ships (INF Code), Resolution MSC.88(71), 1999.
• IMO, EmS Guide, current edition.
• IMO, Medical First Aid Guide for Use in Accidents Involving Dangerous Goods (MFAG), current edition.
• IMO, Code of Practice for Packing of Cargo Transport Units (CTU Code), 2014.
• IMO, IMDG Code Amendment 41-22, in force from 1 January 2024.
• CINS Cargo Incident Notification System Annual Reports.
• IUMI Position Paper on Container Ship Fires, multiple editions.