Safety

SOLAS Chapter VII — Carriage of Dangerous Goods & IMDG Code

Statutory structure of Parts A–D, IMDG Code two-volume framework, 9 hazard classes, UN package testing, and container segregation geometry.

15 min read

Intermediate

Safety

Key Principles at a Glance 6 points

SOLAS Chapter VII governs all dangerous goods carriage, legally structured into four distinct parts: Part A (Packaged Goods / IMDG Code), Part B (Bulk Liquid Chemicals / IBC Code), Part C (Bulk Liquefied Gases / IGC Code), and Part D (Irradiated Nuclear Fuel / INF Code).
The IMDG Code became mandatory in international law on 1 January 2004 under SOLAS Regulation VII/3; Volume 1 governs packaging, tank construction, and consignment, while Volume 2 contains the 18-column Dangerous Goods List (DGL).
Dangerous goods are divided into 9 statutory classes; substances with high, medium, or minor danger are assigned Packing Groups I, II, or III respectively, dictating rigorous drop, leakproofness, and hydrostatic test pressures.
All packages, intermediate bulk containers (IBCs), and portable tanks must carry certified UN specification markings and diamond hazard placards engineered to withstand at least 3 months continuous immersion in seawater.
Segregation between incompatible dangerous goods follows a four-tier statutory distance matrix: "Away from" (3 m), "Separated from" (6 m / 1 bulkhead), "Separated by a complete compartment", and "Separated longitudinally by an intervening compartment".
Port State Control officers possess statutory powers under Regulation 8 to detain any vessel where "clear grounds" demonstrate that crew cannot execute IMDG Emergency Schedules (EmS) or Medical First Aid Guide (MFAG) protocols.

1. Chapter VII Statutory Architecture & The Four Mandatory Codes

PART A Packaged Goods (IMDG Code)

PART B Bulk Liquid Chemicals (IBC Code)

PART C Liquefied Gases (IGC Code)

PART D Nuclear Cargoes (INF Code)

Statutory Scope & Legal Framework

SOLAS Chapter VII provides the overarching international legal convention for transporting dangerous materials across the high seas. While MARPOL Annex III regulates packaged harmful substances strictly to prevent ocean pollution, SOLAS Chapter VII regulates dangerous goods to preserve vessel seaworthiness, fire safety, and human life.

The chapter is structurally divided into four parts, each referencing an exhaustive, mandatory technical safety code that governs ship design, tank containment barriers, and cargo operational handling.

Figure 1: SOLAS Chapter VII Statutory Architecture. The four distinct parts mandate specialized naval architecture: Part A (Container/General cargo under IMDG), Part B (Double-hull parcel chemical tankers under IBC), Part C (Low-temperature gas carriers under IGC), and Part D (Dedicated high-security nuclear fuel carriers under INF).

Comparison of the Four Statutory Codes

SOLAS VII Part	Governing Code	Vessel Structural / Tank Requirements	Statutory Certification Issued
Part A (Packaged Goods)	IMDG Code (Vols 1 & 2)	Cellular container guides, cargo hold fire extinguishing (fixed $CO_2$ or water spray), explosion-proof electrical fittings (IEC 60092-506), and mechanical bilge drainage.	Document of Compliance for Ships Carrying Dangerous Goods (SOLAS II-2/19).
Part B (Liquid Chemicals)	IBC Code (International Bulk Chemical)	Ship Types 1, 2, 3 based on hazard; double bottoms ($B/15$) and side wings ($B/5$); stainless steel/coated tanks, independent stripping, and inert gas blankets.	International Certificate of Fitness for the Carriage of Dangerous Chemicals in Bulk (COF).
Part C (Liquefied Gases)	IGC Code (International Gas Carrier)	Ship Types 1G, 2G, 2PG, 3G; independent Type A, B, C tanks or membrane systems; secondary barriers, cryogenic insulation, and re-liquefaction plants.	International Certificate of Fitness for the Carriage of Liquefied Gases in Bulk.
Part D (Nuclear Cargoes)	INF Code (Classes 1, 2, 3)	Enhanced structural collision protection, independent dual electrical generating sets, emergency floodable hold piping, and satellite tracking telemetry.	International Certificate of Fitness for the Carriage of INF Cargo.

2. IMDG Code Two-Volume Architecture & UN Packaging Testing

VOL 1 Parts 1, 2, 4, 5, 6, 7

VOL 2 Part 3 (Dangerous Goods List)

18 COLS DGL Coded Information Columns

3 MONTHS Seawater Mark Durability Rule

Two-Volume Architecture & The Dangerous Goods List

The IMDG Code is published in two comprehensive volumes supplemented by the IMDG Code Supplement (which houses the Emergency Response Procedures for Ships Carrying Dangerous Goods, EmS Guide, and Medical First Aid Guide, MFAG).

Volume 2, Part 3 contains the central operational heartbeat of the Code: the Dangerous Goods List (DGL). Structured across 18 distinct columns, it assigns every substance an individual UN Number, Proper Shipping Name (PSN), Class, Subsidiary Risks, Packing Group, Special Provisions, Limited Quantities, Packing Instructions, IBC Rules, Tank Provisions, EmS Numbers, and Stowage & Segregation Codes.

Figure 2: UN Specification Packaging & Marking Engineering. Left: 200L 1A1 tight-head steel drum with decoded UN mark, certified for drop and hydrostatic pressures. Right: 1,000L 31HA1 composite IBC with outer steel cage, inner HDPE bottle, and 2.5/5.0-year periodic inspection mandates.

Chemical package labels with hazard diamonds — **Reference photo (course notes):** real package labels — hazard diamonds, handling marks and instructions as the surveyor reads them. Source: Kunjal Shah Part 4 — SOLAS, MARPOL & STCW.

The Five Core Pillars of the IMDG Code

1. Classification

Assigning dangerous goods to one of 9 hazard classes and determining appropriate Packing Groups (I, II, III) based on flashpoint, toxicity, and reactivity.

2. Packaging & Tanks

Mandating certified UN specification packaging, IBCs, and portable tanks that have passed standardized drop, stacking, and hydrostatic pressure tests.

3. Marking & Labelling

Ensuring packages carry the UN Number, Proper Shipping Name, primary and secondary diamond hazard placards that survive 3 months seawater immersion.

4. Documentation

Requiring the Multimodal Dangerous Goods Form (MDGF), signed Container Packing Certificate (CPC), and Dangerous Goods Manifest (DGM) before vessel departure.

5. Segregation

Enforcing physical separation distances on deck and inside cargo holds to prevent explosive, toxic, or exothermic reactions between incompatible chemicals.

3. The 9 Dangerous Goods Classes, Packing Groups & Placarding

9 CLASSES IMDG Hazard Divisions

PG I High Danger (1.8 m Drop Test)

PG II Medium Danger (1.2 m Drop)

PG III Minor Danger (0.8 m Drop)

Comprehensive Review of the 9 IMDG Classes

Classification under the IMDG Code is based on the inherent physical, chemical, and biological hazards posed during sea transit. Dangerous goods are divided into nine classes, several of which are subdivided into specialized divisions reflecting precise reaction dynamics.

Figure 3: The Nine IMDG Dangerous Goods Classes & Marine Pollutant Diamond Placards. Standard container placards measure $250 imes 250 ext{ mm}$ and must be posted on all four sides of a freight container or tank. Markings must remain intact and legible following three months continuous immersion in the sea.

Packing Group Criteria & Engineering Test Rigor

Packing Group	Degree of Danger	Drop Test Height	Hydrostatic Leak Test	Exempted IMDG Classes
Packing Group I (X)	Great Danger (e.g. Sodium cyanide, Nitroglycerin solution, high toxic corrosives).	1.8 metres onto rigid steel plate.	250 kPa minimum (held for 5 minutes without weeping).	The Packing Group concept does not apply to: • Class 1 (Explosives) • Class 2 (Gases) • Class 5.2 (Organic Peroxides) • Class 6.2 (Infectious Substances) • Class 7 (Radioactive Materials)
Packing Group II (Y)	Medium Danger (e.g. Petrol, Kerosene, Nitric acid, Hydrochloric acid).	1.2 metres onto rigid steel plate.	100 kPa minimum.
Packing Group III (Z)	Minor Danger (e.g. Diesel fuel, Gas oil, Phosphoric acid solutions).	0.8 metres onto rigid steel plate.	100 kPa minimum.

Thermal Runaway in Class 5.2: Self-Accelerating Decomposition Temperature (SADT)

Class 5.2 Organic Peroxides are thermally unstable and undergo self-accelerating exothermic decomposition. If ambient hold temperature exceeds the Control Temperature, emergency refrigeration procedures must be initiated. If the cargo reaches its Emergency Temperature (typically 5°C to 10°C below its SADT), explosive decomposition, vessel fire, or toxic gas blowout is imminent. Jettisoning procedures under the Master's authority must be prepared.

4. Container Segregation Geometry, EmS Response & PSC Detention

TABLE 7.2 IMDG Segregation Matrix

3 m / 6 m "Away From" vs "Separated From"

EmS GUIDE Emergency Schedules (Fire & Spillage)

REG 8 PSC Operational Detention Power

Container Ship Cell Guide Segregation Geometry

On modern cellular container vessels, segregation is not determined by simple visual distance but by a mathematically defined Bay-Row-Tier slot coordinate matrix under IMDG Chapter 7.2. Incompatible dangerous goods must be separated by specific container spaces or fire-resistant, gas-tight steel bulkheads (A-60 insulation class).

Figure 4: Container Cell Guide Segregation Geometry & IMDG EmS Fire/Spillage Intervention. Left: Cross-section of container stacks showing horizontal slot buffer separation on deck and vertical A-60 steel bulkhead segregation under deck. Right: Statutory EmS emergency schedules and Port State Control operational detention powers under Regulation 8.

IMDG Chapter 7.2 Four-Tier Segregation Hierarchy

Segregation Term	Code	Distance / Boundary Requirement (Packaged)	Container Vessel Cell Separation
"Away from"	1	Effectively segregated so that incompatible materials cannot react dangerously; min 3 metres separation.	One container space horizontally (either forward/aft or athwartships) on deck; or separate vertical rows under deck.
"Separated from"	2	Stowed in different compartments or holds, or separated by a min distance of 6 metres horizontally on deck.	At least two container slots athwartships or forward/aft on deck; or separated by a fire-resistant A-60 bulkhead under deck.
"Separated by a complete compartment or hold from"	3	Either a vertical or longitudinal separation by an intervening complete cargo hold or deck space.	Not permitted in the same cargo hold; must be separated by an intervening cargo hold or weather deck gap.
"Separated longitudinally by an intervening complete compartment or hold from"	4	Longitudinal separation only; intervening hold must be free of incompatible dangerous materials.	Minimum one full container bay length (40-foot bay) intervening with separate hatch covers and bulkheads.

Surveyor Oral & Written Examination Bank

What is the legal relationship between SOLAS Chapter VII and MARPOL Annex III?

Both conventions share the mandatory technical framework of the IMDG Code. However, SOLAS Chapter VII governs carriage safety—preventing vessel fires, structural explosions, toxic poisoning, and hull loss. MARPOL Annex III governs marine environmental protection—preventing the jettisoning or accidental release of packaged harmful substances that bio-accumulate or poison marine ecosystems.

What three documents must be present on board before a ship carrying packaged dangerous goods departs?

1. The Multimodal Dangerous Goods Form (MDGF) signed by the shipper certifying correct packaging and placarding. 2. The Container Packing Certificate (CPC) signed by the container packer confirming internal cargo securing and segregation. 3. The Dangerous Goods Manifest (DGM) or detailed stowage plan prepared by the ship's officers listing UN numbers, PSN, classes, packing groups, weights, and exact bay-row-tier slot locations on board.

Explain the statutory significance of the 3-month seawater immersion rule for dangerous goods markings.

Under SOLAS VII Regulation 4 and IMDG Code 5.2.2.1.1.1, all package markings, Proper Shipping Names, UN number labels, and hazard placards must be engineered with adhesive, ink, and base materials capable of surviving at least 3 months continuous immersion in the sea. This ensures that lost-overboard containers or washed-up packages can be immediately identified by emergency coastal responders.

How is an EmS number structured, and where is it found?

The EmS (Emergency Schedules) code is published in Column 15 of the Dangerous Goods List (DGL) and comprises two parts: a Fire Schedule (e.g. F-A to F-J) and a Spillage Schedule (e.g. S-A to S-Z). The letters guide ship officers to specific action cards in the IMDG Code Supplement detailing emergency cooling methods, protective gear, and whether water, foam, or inert gas should be used.

Under what circumstances can a Port State Control Officer detain a vessel under SOLAS Chapter VII?

Under Regulation 8 (Operational Requirements), a PSCO can detain the vessel if "clear grounds" exist that the Master or crew are not familiar with essential shipboard dangerous goods procedures—such as failure to produce the Dangerous Goods Manifest, improper segregation of incompatible containers, lack of certified PPE, or inability to demonstrate EmS response. The ship is forbidden to sail until all defects are resolved.