The 9 Dangerous Goods Classes and Their Subdivisions, Set by the ADG Code (Edition 7.9, 2024)

Published: June 11, 2025| Last Updated: July 26, 2025

Dangerous Goods (DG) are substances and articles posing significant risks to health, safety, property, or the environment during transport. Effective management, starting with correct classification and identification, is paramount for safe and compliant logistics operations. In Australia, the transport of dangerous goods by road and rail is governed by the Australian Code for the Transport of Dangerous Goods by Road & Rail (ADG Code), developed by the National Transport Commission (NTC) in alignment with international UN standards. This article provides a comprehensive summary of the nine dangerous goods classes outlined in the ADG Code, Edition 7.9, focusing on classification criteria, subdivisions, packing groups, and labelling requirements crucial for logistics professionals and businesses. While this summary offers actionable insights, it is essential to consult the full, latest version of the ADG Code.

Sources and Resources:

• Australian Dangerous Goods Code – The National Transport Commission’s official page for administering the latest ADG code documentation
• Australian Code for the Transport of Dangerous Goods by Road & Rail Edition 7.9, 2024.pdf – Edition 7.9 of the ADG Code, the latest available version as of July 26, 2025

Key Concepts:

• Classes: The primary categorisation based on the main type of hazard (ADG Code, Section 2.0.1.1)
• Subdivisions: Sub-categories within some classes, refining the specific hazard (ADG Code, Section 2.0.1.1)
• Packing Groups (PG): Assigned to substances in many classes (excluding Classes 1, 2, 6.2, 7, and self-reactive/organic peroxides) to indicate the degree of danger:
  • PG I: High danger.
  • PG II: Medium danger.
  • PG III: Low danger.

  (ADG Code, Section 1.2.1 definitions; 2.0.1.3). PG assignment dictates packaging standards and some transport conditions.

• Subsidiary Hazards: Many dangerous goods possess more than one hazard. The ‘subsidiary hazard’ is the secondary danger type. The precedence of hazards is defined (ADG Code, Section 2.0.3) and subsidiary hazards must also be identified and labelled (ADG Code, Section 5.2.2.1.2).
• Hazard Labels: Standardised diamond-shaped labels communicating the primary and any subsidiary hazards through distinct colours, symbols, and the Class/Division number. Specifications are detailed in ADG Code, Section 5.2.2. For specific labelling instructions, refer to Chapter 5 of the ADG code.

The Nine Dangerous Goods Classes

DG Class 1: Explosives

Chapter 2.1

• Definition: Substances (solid or liquid) or articles capable of producing gas at such a temperature, pressure, and speed as to cause damage to surroundings, including pyrotechnic substances designed for heat, light, sound, gas, or smoke effects (ADG Code, Section 2.1.1.1).
• Subdivisions:
  • 1.1: Mass explosion hazard.
  • 1.2: Projection hazard, no mass explosion.
  • 1.3: Fire hazard with minor blast/projection, no mass explosion.
  • 1.4: No significant hazard (effects largely confined to package).
  • 1.5: Very insensitive substances with mass explosion hazard.
  • 1.6: Extremely insensitive articles, no mass explosion hazard.
• Packing Groups: Not applicable to Class 1.
• Primary Hazard Label: Orange with an exploding bomb symbol and subdivision number.
• Subsidiary Hazards: Possible (e.g., toxicity).
• Key Classification Notes: Includes Compatibility Groups A–S (excluding I, M, O, P, Q, R).

Class 1 is reserved for explosives, defined by the ADG as substances or items—like fireworks, ammunition, or detonators—that can rapidly produce gas and cause damage through heat, pressure, or sound. They’re grouped into six subdivisions based on how dangerous they are. Some pose a mass explosion risk (like subdivision 1.1), while others only have fire or projection hazards, or are extremely unlikely to explode at all (like subdivision 1.6).

Unlike other dangerous goods, explosives aren’t sorted into packing groups. Instead, they’re also organised into compatibility groups (A to S, with some letters excluded) to ensure that only safe combinations are stored or shipped together. The hazard label for all explosives is orange, with an exploding bomb icon and a number showing the subdivision. Some may also carry extra hazard labels, such as for toxicity.

DG Class 2: Gases

Chapter 2.2

• Definition: Gaseous at 20°C and 101.3 kPa, or have a vapour pressure >300 kPa at 50°C.
• Subdivisions:
  • 2.1: Flammable gases.
  • 2.2: Non-flammable, non-toxic gases.
  • 2.3: Toxic gases.
• Packing Groups: Not applicable.
• Primary Hazard Labels:
  • 2.1: Red with flame symbol.
  • 2.2: Green or yellow with gas cylinder or oxidiser symbol.
  • 2.3: White with skull and crossbones.
• Subsidiary Hazards: Common, requires labelling.
• Key Classification Notes: Hazard precedence is 2.3 > 2.1 > 2.2.

Class 2 covers gases—substances that are either fully gaseous at room temperature and pressure, or become gas-like under normal transport conditions. This includes things like propane, oxygen, and chlorine. Gases are divided into three types: flammable (2.1), non-flammable and non-toxic (2.2), and toxic (2.3). Each type comes with its own risks, from fire and explosion to poisoning or suffocation.

Gases don’t use packing groups, but many have multiple hazards that must be clearly labelled. Hazard labels are colour-coded—red for flammable, green or yellow for inert or oxidising gases, and white for toxic ones. If a gas has more than one hazard, the most dangerous one always takes priority when determining how it should be handled and contained.

DG Class 3: Flammable Liquids

Chapter 2.3

• Definition: Liquids giving off flammable vapour at ≤ 60°C (closed-cup).
• Subdivisions: None.
• Packing Groups:
  • PG I: FP < 23°C, BP ≤ 35°C.
  • PG II: FP < 23°C, BP > 35°C.
  • PG III: FP ≥ 23°C and ≤ 60°C, BP > 35°C.
• Primary Hazard Label: Red with flame symbol and “3”.
• Subsidiary Hazards: Possible.
• Key Classification Notes: Flash point and boiling point are key.

Class 3 includes flammable liquids—liquids that can release enough vapour to ignite at temperatures of 60°C or below. These can range from fuels like petrol to alcohol-based products and solvents. While there are no subdivisions, flammable liquids are sorted into three packing groups based on how easily they ignite and how quickly they evaporate.

The two key factors are flash point (the lowest temperature at which a liquid gives off vapour that can ignite) and boiling point (the temperature at which the liquid turns into gas). Packing Group I is for the most dangerous: liquids that both ignite easily (flash point under 23°C) and boil at low temperatures (35°C or less), meaning they evaporate quickly and are extremely volatile. PG II also includes liquids with very low flash points, but they boil at safer, higher temperatures—so they don’t vaporise as rapidly. PG III is for liquids that still ignite easily, but only at slightly higher temperatures (23–60°C), and they also boil above 35°C, making them more stable by comparison.

DG Class 4: Flammable Solids

Chapter 2.4

• Definition: Includes flammable solids, substances liable to spontaneous combustion, and substances which emit flammable gas when wet.
• Subdivisions:
  • 4.1: Flammable solids, self-reactives, desensitised explosives, polymerizing substances.
  • 4.2: Spontaneously combustible substances.
  • 4.3: Dangerous when wet substances.
• Packing Groups: Applicable (PG I, II, III).
• Primary Hazard Labels:
  • 4.1: Red/white striped.
  • 4.2: White over red split label.
  • 4.3: Blue label with flame symbol.
• Subsidiary Hazards: Possible.
• Key Classification Notes: Temperature control may be required.

Class 4 covers flammable solids—substances that ignite easily, burn fiercely, or react dangerously when exposed to air or water. It’s split into three subdivisions: 4.1 includes flammable solids and unstable or self-reactive materials; 4.2 includes substances that can spontaneously catch fire when exposed to air; and 4.3 includes materials that release flammable gas on contact with water.

Packing groups (I, II, or III) reflect how severe the hazard is, with Group I being the most dangerous. Proper storage is critical—4.2 materials must be protected from air, while 4.3 must be kept completely dry. Labels differ by subdivision: red and white stripes for 4.1, red-over-white for 4.2, and blue for 4.3. Some items may also need temperature control or have secondary hazards that require extra labelling.

DG Class 5: Oxidising Substances & Organic Peroxides

Chapter 2.5

• Definition: Includes oxidisers and thermally unstable organic peroxides.
• Subdivisions:
  • 5.1: Oxidising substances.
  • 5.2: Organic peroxides.
• Packing Groups: PG I–III for 5.1; not applicable for 5.2 (uses Types A–G).
• Primary Hazard Labels:
  • 5.1: Yellow with flame over circle.
  • 5.2: Red/yellow with flame.
• Subsidiary Hazards: Possible.
• Key Classification Notes: Many organic peroxides require temperature control.

Class 5 covers oxidising substances and organic peroxides—materials that may not burn on their own but can cause or accelerate fires when combined with other substances. Subdivision 5.1 includes oxidisers like ammonium nitrate that release oxygen and make other materials ignite more easily. Subdivision 5.2 includes organic peroxides, which are chemically unstable and can explode, burn violently, or give off harmful vapours if not handled properly.

Packing groups I to III apply to oxidisers depending on how reactive they are, while organic peroxides are classified by Types A to G based on how dangerous they are under transport conditions. Labels are distinct: 5.1 uses a yellow background with a flame-over-circle symbol; 5.2 uses a red-over-yellow label with a flame. Many peroxides are sensitive to heat and must be kept within strict temperature ranges during transport. Subsidiary hazards like toxicity or flammability may also apply.

DG Class 6: Toxic & Infectious Substances

Chapter 2.6

• Definition: Toxic or infectious to humans.
• Subdivisions:
  • 6.1: Toxic substances.
  • 6.2: Infectious substances.
• Packing Groups: PG I–III for 6.1; Category A/B for 6.2.
• Primary Hazard Labels:
  • 6.1: White with skull and crossbones.
  • 6.2: White with biohazard symbol.
• Subsidiary Hazards: Possible.
• Key Classification Notes: 6.2 governed by pathogen category.

Class 6 includes toxic and infectious substances—materials that can harm or kill people if inhaled, swallowed, or absorbed through the skin. Subdivision 6.1 covers toxic chemicals like pesticides or cyanides, while 6.2 includes infectious materials that contain or are expected to contain harmful pathogens, such as certain medical waste or biological samples.

Toxic substances (6.1) are grouped into Packing Groups I, II, or III based on how poisonous they are. Infectious substances (6.2) are categorised as either Category A (high risk of severe disease) or Category B (lower risk). Labels differ by subdivision: 6.1 uses a white label with a skull and crossbones, while 6.2 uses a white label with a biohazard symbol. Some materials may have additional hazards that require extra labelling.

DG Class 7: Radioactive Material

Chapter 2.7

• Definition: Contains radionuclides above threshold activity.
• Subdivisions: None.
• Packing Groups: Not applicable.
• Primary Hazard Labels: WHITE I, YELLOW II, YELLOW III, with Transport Index and CSI.
• Subsidiary Hazards: Possible.
• Key Classification Notes: Regulated by ARPANSA transport code.

DG Class 8: Corrosive Substances

Chapter 2.8

• Definition: Cause irreversible skin damage or metal damage.
• Subdivisions: None.
• Packing Groups:
  • PG I: Severe.
  • PG II: Moderate.
  • PG III: Mild.
• Primary Hazard Label: Black and white with test tubes on hand and metal.
• Subsidiary Hazards: Possible.
• Key Classification Notes: Based on skin damage/corrosion data.

Class 8 includes corrosive substances—chemicals that can permanently damage skin, eyes, or metal surfaces on contact. Common examples include strong acids, alkalis, and industrial cleaners. These substances are dangerous not just to people but also to containers, vehicles, and other nearby goods if a leak occurs.

They’re sorted into Packing Groups I, II, or III based on how quickly and severely they cause damage—PG I being the most aggressive. The standard label is black and white, showing test tubes pouring onto a hand and a metal bar. Because corrosives can eat through packaging or react with incompatible materials, secure containers and proper segregation are critical. Some may also carry secondary hazards, such as flammability or toxicity.

DG Class 9: Miscellaneous Dangerous Goods

Chapter 2.9

• Definition: Present hazards not covered elsewhere.
• Subdivisions: None.
• Packing Groups: Sometimes applicable (e.g., for environmentally hazardous substances).
• Primary Hazard Label: White with black stripes, “9” underlined.
• Subsidiary Hazards: Sometimes applicable.
• Key Classification Notes: Includes lithium batteries, elevated temperature materials, asbestos, dry ice, GMOs, etc.

DG Class 9 covers miscellaneous dangerous goods—substances or articles that pose transport risks but don’t fit into any other class. This includes a wide range of items like lithium batteries, dry ice, environmentally hazardous substances, genetically modified organisms (GMOs), and materials shipped at elevated temperatures.

There are no formal subdivisions, and packing groups only apply to certain items like marine pollutants. The standard label is a white diamond with black vertical stripes on the top half and the number “9” underlined at the bottom. Because Class 9 includes such varied hazards, handling and labelling requirements can differ significantly between items, and often need to be assessed case by case.

Closing Notes and Additional Resources

Correct classification, assignment of packing groups, identification of subsidiary hazards, and application of the correct hazard labels are essential for the safe and compliant transport of dangerous goods under the ADG Code. These fundamentals support every part of the logistics process—from choosing the right packaging and segregation practices to ensuring accurate documentation—ultimately helping to protect people, property, and the environment.

This article is designed to summarise key responsibilities and classifications under the ADG Code, but it is not a substitute for official legislation. For definitive guidance, you should always consult the Australian Code for the Transport of Dangerous Goods by Road & Rail and any applicable state or territory regulations.

If you need help with classification, labelling, or operational requirements, contact your local competent authority. A current list of contacts is available at:
ntc.gov.au/competent-authorities-panel-contact-details.