Dangerous Goods Classes Explained: What Class Is Your Load?

The Australian Dangerous Goods Code divides all dangerous goods into 9 classes based on the nature of the hazard they present. If you are a driver, transport planner, or consignor in Australia, you need to know which class your load belongs to — because classification determines packaging requirements, vehicle placarding, training requirements, segregation rules, and route restrictions. Get the class wrong and you have a compliance failure on your hands.

Why Class Matters: The Foundation of ADG Code Compliance

Classification is the first step in every dangerous goods transport operation. Before packaging, labelling, vehicle placarding, or training can begin, the consignor — the person sending the goods — must correctly identify the class of the substance using the ADG Code Dangerous Goods List. The List assigns each UN number to a specific class and specifies the packaging, marking, and transport restrictions for that substance.

Incorrect classification is a direct breach of the ADG Code and creates liability for the consignor, transporter, and operator under Chain of Responsibility (COR) legislation. NHVR and NSW EPA inspectors check classification compliance regularly.

Class 1: Explosives

What they are: Substances and articles designed to produce a practical explosive effect through chemical reaction. Includes fireworks, ammunition, explosives used in mining and demolition, and signal flares.

Examples: TNT, dynamite, fireworks, ammunition, blasting caps, detonators, flares

Key hazard: Explosion risk. A Class 1 load in an accident poses an immediate danger to people and infrastructure.

Transport restrictions: Highly restricted. Class 1 transport requires special licensing, specific vehicle types, route authorisation, and often police escort. Class 1.1 (mass explosion hazard) materials have additional restrictions including prohibition from certain roads and areas.

What drivers need to know: Class 1 loads are beyond the scope of a standard TLILIC0001 DG Licence — they require additional specialist training and authorisation. Most small transport operators will not encounter Class 1.

Class 2: Gases

What they are: Gases at elevated pressure or dissolved in solution. Includes compressed gases (oxygen, nitrogen, acetylene), liquefied gases (LPG, propane, butane), and refrigerated liquefied gases (liquid nitrogen).

Examples: LPG (bottled gas), oxygen (welding/medical), acetylene (welding), compressed air, ammonia gas, chlorine gas

Key hazard: Pressure release and/or flammability. A damaged Class 2 container can rupture explosively, releasing gas at high pressure.

Transport restrictions: Specific vehicle configurations required (certified gas carrier vehicles). Route restrictions apply in some areas. Segregation from incompatible goods required.

What drivers need to know: LPG and oxygen are common Class 2 loads. The TLILIC0001 course covers Class 2 transport in detail. Drivers must understand pressure vessel safety and emergency response for a gas leak.

Class 3: Flammable Liquids

What they are: Liquids with a flash point below 61°C. Flash point is the lowest temperature at which the liquid gives off enough vapour to form an ignitable mixture in air.

Examples: Petrol, diesel, paint, methylated spirits, acetone, thinners, kerosene, light fuel oil

Key hazard: Fire. Class 3 liquids ignite easily and burn vigorously. A spill of Class 3 material in a vehicle fire scenario can escalate rapidly.

Transport restrictions: Specific tank construction required. No smoking, naked flames, or hot work within a safety zone around a Class 3 tanker. Ventilation and grounding requirements for loading/unloading. Tunnel restrictions apply in Sydney.

What drivers need to know: Class 3 is one of the most frequently transported dangerous goods classes in Australia. Fire safety and spill containment are the primary driver concerns. The TLILIC0001 course covers Class 3 extensively.

Class 4: Flammable Solids

What they are: Solids that are readily combustible or will undergo spontaneous chemical change. Divided into three divisions: self-reactive substances (Class 4.1), pyrophoric solids (Class 4.2), and materials that emit flammable gas when wet (Class 4.3).

Examples: Matches, phosphorus, magnesium powder, calcium carbide, wet charcoal, metallic sodium

Key hazard: Spontaneous ignition or rapid combustion. Some Class 4.2 materials (pyrophoric solids) will ignite spontaneously if exposed to air or moisture.

Transport restrictions: Specific packaging to prevent contact with water, air, or incompatible materials. Vehicle ventilation requirements. Segregation from water sources and incompatible goods.

What drivers need to know: Class 4 is less common than Class 3 but requires careful handling. Understanding the specific sub-class (4.1, 4.2, 4.3) determines the emergency response to a spill or accident.

Class 5: Oxidising Substances and Organic Peroxides

What they are: Substances that readily give off oxygen or other oxidising elements, causing or enhancing combustion of other materials. Divided into two divisions: oxidising substances (Class 5.1) and organic peroxides (Class 5.2).

Examples: Household bleach, pool chlorine, hydrogen peroxide, fertilisers containing nitrates, calcium hypochlorite

Key hazard: Accelerated combustion. Class 5 materials do not burn themselves but cause other materials to burn faster and hotter. A small fire involving a Class 5 material becomes a major fire quickly.

Transport restrictions: Strict segregation from flammable materials (Class 3, 4, 9). No smoking or hot work in the vicinity. Specific labelling and placarding. Vehicle construction and ventilation requirements.

What drivers need to know: The most critical rule for Class 5 transport is segregation — keep it away from fuels, solvents, paints, and other flammable goods. This is a heavily audited compliance point.

Class 6: Toxic and Infectious Substances

What they are: Substances that are poisonous or cause disease. Divided into two divisions: toxic substances (Class 6.1) — including pesticides, herbicides, and pharmaceutical ingredients — and infectious substances (Class 6.2) — including medical waste and blood products.

Examples: Pesticides, herbicides, cyanides, strychnine, arsenic compounds, medical waste, blood products, laboratory cultures

Key hazard: Poisoning or infection. Exposure to Class 6 material through inhalation, ingestion, or skin contact can cause acute illness or death. Infectious materials (Class 6.2) pose additional biological hazard.

Transport restrictions: Specialist packaging required. Full PPE and respiratory protection may be needed for emergency response. Vehicle decontamination requirements after transport. Segregation from food and water supplies.

What drivers need to know: Class 6 demands high respect. The TLILIC0001 course covers the emergency response procedures in detail. If you transport Class 6 materials, you must carry the Emergency Procedure Guide for that specific UN number — not just in the vehicle but immediately accessible in the cab.

Class 7: Radioactive Material

What they are: Materials that spontaneously emit ionising radiation. Most Class 7 transport in Australia is medical isotopes used in hospitals and diagnostic facilities.

Examples: Medical isotopes (cobalt-60, molybdenum-99), research materials, industrial gauges (rarely transported by road)

Key hazard: Ionising radiation exposure. Radioactive material poses a health hazard through exposure (external) or if inhaled or ingested (internal).

Transport restrictions: Extremely strict. Class 7 transport in Australia is regulated by the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) in addition to the ADG Code. Specialist vehicles, shielding, and documentation required. Regular transport inspection and authorisation required.

What drivers need to know: Class 7 is highly specialised. If your operation involves Class 7 transport, ARPANSA licensing and specialist training are mandatory. This is beyond the scope of standard TLILIC0001 training.

Class 8: Corrosives

What they are: Substances that cause visible destruction of human skin tissue (chemical burn) or severe corrosion of ship/vehicle structural materials.

Examples: Sulphuric acid, hydrochloric acid, sodium hydroxide (caustic soda), battery acid, drain cleaners, rust removers, water treatment chemicals

Key hazard: Chemical burn. Spilled or leaked corrosive material burns skin and eyes on contact and corrodes container materials and vehicle structure.

Transport restrictions: Specific tank construction (often stainless steel or specialist coatings to resist corrosion). Full PPE and eye wash equipment required on board. Segregation from flammable materials and incompatible goods. Ventilation and drainage requirements for loading areas.

What drivers need to know: Class 8 is extremely common in NSW industrial transport — battery acid, industrial chemicals, waste acids. The TLILIC0001 course covers Class 8 extensively because drivers frequently encounter it. Understand the emergency response (immediate flushing with large volumes of water for skin contact, emergency eyewash deployment) and segregation rules.

Class 9: Miscellaneous Dangerous Goods

What they are: Substances that do not fit neatly into Classes 1–8 but still present a hazard during transport. A catch-all category that includes respiratory irritants, substances harmful to the aquatic environment, and items with specific handling requirements.

Examples: Lithium batteries (Class 9 when transported by air or in certain quantities by road), dry ice, asbestos, magnetised materials, heat-sensitive items, shark repellent (yes, this is a real Class 9 item)

Key hazard: Varies by item — but typically respiratory irritation, environmental contamination, or special storage/temperature requirements.

Transport restrictions: Highly variable depending on the specific substance. Always check the ADG Code Dangerous Goods List and the Emergency Procedure Guide for the specific UN number.

What drivers need to know: Class 9 items are less common than Classes 3 and 8 but can surprise you. Lithium batteries (phones, power banks, laptops) shipped in bulk for recycling or manufacturing are increasingly transported under Class 9 restrictions. Always verify your load’s exact class before departing.

What About Sub-Risks?

Some substances have two hazards — a primary hazard (the class) and a secondary hazard (the sub-risk). For example, a substance might be primarily a flammable liquid (Class 3) but also toxic (Class 6 sub-risk). In this case, the vehicle would display the Class 3 placard plus a Class 6 sub-risk placard, and the consignment note would document both hazards.

Sub-risks affect segregation rules, emergency response, and PPE requirements. The ADG Code Dangerous Goods List specifies sub-risks for each UN number.

How to Identify the Class of Your Load

Classification is the consignor’s responsibility — the person sending the goods. They use the ADG Code Dangerous Goods List to find the UN number of the substance, and the List tells them the class, packing group, and transport restrictions.

As a driver or operator:

• Check the consignment note for the UN number and class
• Read the Emergency Procedure Guide for that UN number
• Verify that the vehicle placarding matches the class on the consignment note
• If anything is unclear or doesn’t match, do not depart — contact your dispatcher or the consignor

As a consignor:

• Look up the substance name in the ADG Code Dangerous Goods List
• Find the correct UN number and classification
• Document the class, packing group, and proper shipping name on the consignment note
• Ensure packaging matches the packing group requirements
• Provide the correct Emergency Procedure Guide to the driver

For regulatory guidance on classification, refer to NSW EPA and the National Transport Research Organisation (NTRO) — the body that publishes the ADG Code.

Key Takeaways

• The ADG Code defines 9 classes of dangerous goods based on hazard type
• Classes 1–9 each have distinct transport restrictions, packaging, and emergency response requirements
• Correct classification is the consignor’s responsibility — determined using the ADG Code Dangerous Goods List
• Drivers must verify the class matches the consignment note and vehicle placards before departing
• Sub-risks (secondary hazards) add additional transport restrictions
• Wrong classification = compliance failure and COR liability
• Kells Safety Centre teaches classification as part of the TLILIC0001 DG Licence course

Frequently Asked Questions

What is the difference between class and packing group?

Class refers to the type of hazard (flammable liquid, toxic, corrosive, etc.). Packing group (I, II, or III) refers to the degree of danger within that class — Class 3 Packing Group I is a highly flammable liquid (flash point < 0°C), while Class 3 Packing Group III is a flammable liquid with a flash point closer to 61°C. Different packing groups have different packaging and placarding requirements.

Can a substance belong to more than one class?

A substance has one primary class but may have a sub-risk (secondary hazard). For example, a substance might be Class 3 (flammable liquid) with Class 6 sub-risk (toxic). The primary class determines vehicle placarding, but the sub-risk affects segregation and emergency response.

Who is responsible for correct classification?

The consignor — the person or company sending the goods — is responsible for correct classification. They must use the ADG Code Dangerous Goods List to determine the UN number, class, and packing group. Incorrect classification is a consignor liability and a Chain of Responsibility breach.

How do drivers check the class of their load?

The consignment note provided by the consignor must state the UN number, proper shipping name, class, and packing group. The vehicle placards must match the class. If there is any discrepancy or uncertainty, do not depart — contact your dispatcher or the consignor for clarification.

Is Class 9 less dangerous than other classes?

No — Class 9 items still present hazards, they just don’t fit neatly into Classes 1–8. Lithium batteries (Class 9) have caused fires in air cargo and require specific transport precautions. Always treat Class 9 items according to their Emergency Procedure Guide, not your assumptions.

Where can I learn dangerous goods classification in NSW?

The TLILIC0001 Dangerous Goods Driver Licence course at Kells Safety Centre covers classification in detail — how to read the ADG Code Dangerous Goods List, how to identify class and packing group, and how classification affects transport restrictions. Delivered at Wetherill Park and Wollongong. The DG Awareness course also covers classification for handlers and warehouse workers.