PART 2: CLASSIFICATION

Classification is the foundation of dangerous goods regulation. By determining the intrinsic hazards of a substance or article, classification dictates how the material must be packaged, labeled, marked, segregated, stowed, documented, transported, and handled during emergencies.
Without proper classification, no dangerous goods can legally enter the transport chain because all subsequent requirements depend on this initial step.

Chapter 2.0 – Introduction

Classification is the process of identifying and categorizing substances or articles according to the risk they pose during transport. The IMDG Code groups dangerous goods into nine hazard classes, some with subdivisions, based on their primary dangerous properties.

Purpose of Classification

• Provides a common hazard language globally

• Determines the appropriate packaging requirements

• Ensures correct hazard communication through labels, marks, and placards

• Governs segregation rules to avoid dangerous reactions on board ships

• Influences emergency response procedures, such as firefighting and spill control

• Determines whether the material may be transported at all

Regulatory Requirement

Goods without an approved UN classification:

• cannot be declared,

• cannot be documented,

• cannot be accepted,

• cannot be shipped.

Misclassification is considered a major violation, exposing the shipper and carrier to:

• cargo rejection,

• fines,

• criminal liability,

• vessel detention,

• insurance invalidation.

Classification is therefore not administrative—it is a legal and safety-critical obligation.

Chapter 2.1 – Class 1: Explosives

Explosives are substances or articles capable of producing rapid gas expansion resulting in pressure waves, high temperatures, and fragmentation. Due to their destructive potential, explosives require stringent handling, segregation from ignition sources, and temperature stability.

Divisions of Class 1

The divisions reflect the type and severity of hazard:

Controls

• Temperature stability: prevent decomposition or self-reaction

• Shock & friction prevention: avoid triggers

• Segregation: isolate from heat, sparks, oxidizers, fuels

Explosives demand special stowage, trained personnel, and strict inventory control.

Chapter 2.2 – Class 2: Gases

Gases are dangerous due to pressure, reactivity, and toxic or flammable properties. Even non-toxic gases can displace oxygen, causing suffocation in confined spaces.

Gas Categories

Operational Hazards

• High pressure: cylinder rupture risks

• Combustion: flammable gas ignition

• Asphyxiation: oxygen displacement in enclosed spaces

Proper ventilation, leak detection, and cylinder securing are essential.

Chapter 2.3 – Class 3: Flammable Liquids

Flammable liquids release vapors that can ignite at or below normal temperatures. The critical parameter is flash point—the lowest temperature at which sufficient vapor forms to ignite.

Hazard Determinants

• Flash point

• Boiling point

• Volatility

• Viscosity (affects spill behavior)

Packing Groups (PG)

Proper grounding, ventilation, and temperature control reduce ignition risk.

Chapter 2.4 – Class 4: Flammable Solids

Subclass divisions

These substances require dry handling, airtight packaging, and segregation from moisture.

Chapter 2.5 – Class 5: Oxidizing Substances & Organic Peroxides

Oxidizing substances supply oxygen, increasing combustion risk. Organic peroxides contain both oxidizing properties and thermal instability, making them susceptible to violent decomposition.

Hazards

• Intensify fires

• May self-react or explode under heat

• Generate oxygen-supporting combustion

Control Measures

• Temperature control is essential: exceeding control temperature can cause runaway reactions

• Avoid contamination with fuels or reducing agents

These materials require specialized packaging, insulated containers, and temperature monitoring.

Chapter 2.6 – Class 6: Toxic and Infectious Substances

6.1 Toxic Substances

Poisons harmful to humans by ingestion, inhalation, or skin absorption.
Require airtight packaging, spill prevention, and decontamination readiness.

6.2 Infectious Substances

Contain pathogens such as bacteria, viruses, or prions capable of causing disease.
Require sealed containment, triple packaging, and biohazard labeling.

Primary controls:

• Minimize exposure

• Isolate from personnel

• Prepare emergency medical response

Chapter 2.7 – Class 7: Radioactive Material

Radioactive substances emit ionizing radiation capable of damaging living tissue.

Safety Requirements

• Transport Index (TI): controls exposure limits

• Surface dose rate checks

• Shielding: prevents dangerous radiation levels

• Segregation: distance from personnel-living areas

Radioactive materials demand special approvals, monitoring, and dosimetry.

Chapter 2.8 – Class 8: Corrosives

Corrosive substances cause severe chemical burns to skin and material degradation of metals or containers.

Hazards

• Destruction of tissue on contact

• Weakening of structural materials

• Release of toxic fumes during reactions

Key controls:

• Leak-proof packaging

• Chemical compatibility

• Segregation from reactive materials

Chapter 2.9 – Miscellaneous Dangerous Substances and Articles (Class 9)

Class 9 encompasses substances that present hazards not covered elsewhere.

Examples:

• Lithium batteries: fire/thermal runaway hazard

• Magnetized materials: interfere with navigation instruments

• Environmentally hazardous substances: marine pollutants

These materials require specific labeling and stowage rules depending on their nature.

Chapter 2.10 – Marine Pollutants

Marine pollutants are substances toxic to aquatic organisms, capable of long-term environmental damage.

Regulatory Requirements

• Identified as P in the Dangerous Goods List

• Must display Marine Pollutant mark

• Packaging must prevent leakages into the sea

• Additional UN number marking when applicable

Marine pollutants reinforce the MARPOL objective to prevent marine pollution during sea transport.

PART 2 SUMMARY TABLE