ADR Classes Explained: A Complete Guide to Dangerous Goods Categories

Understand the nine ADR hazard classes, choose packages or tanks training, and compare current GS ADR course options and prices.

Updated 9 October 2026. ADR classes identify the hazard presented by dangerous goods. If you are choosing ADR training, they are a useful starting point for explaining the goods you expect to carry. They do not by themselves confirm every module, examination or transport operation that applies to you.

Before choosing a course, ask your employer or consignor for the dangerous goods information for the work: the UN number and class, whether the goods travel in packages or tanks, and any current ADR card you hold. The GOV.UK ADR driver guide confirms that additional training can be needed according to the goods carried, and the ADR card shows the dangerous goods a driver is allowed to carry.

The nine ADR hazard classes

The Health and Safety Executive lists nine dangerous-goods classes. Some have divisions, which distinguish particular types of hazard within a class. Classification is used to identify the requirements that follow for the goods; the consignor is responsible for classifying the goods and assigning the proper shipping name and UN number.

Class 1 — Explosives

Explosives include substances and articles with an explosive hazard. Class 1 has divisions 1.1 to 1.6.

Class 2 — Gases

Class 2 covers gases. Its divisions include flammable gas, non-flammable non-toxic gas and toxic gas.

Class 3 — Flammable liquids

Class 3 covers flammable liquids.

Class 4 — Flammable solids and related hazards

Class 4 includes flammable solids, substances liable to spontaneous combustion, and substances which emit flammable gas when in contact with water.

Class 5 — Oxidising substances and organic peroxides

Class 5 includes oxidising substances and organic peroxides.

Class 6 — Toxic and infectious substances

Class 6 includes toxic substances and infectious substances.

Class 7 — Radioactive material

Class 7 covers radioactive material.

Class 8 — Corrosive substances

Class 8 covers corrosive substances.

Class 9 — Miscellaneous dangerous goods

Class 9 covers miscellaneous dangerous goods that do not fall within Classes 1 to 8.

How the classes help you select training

GOV.UK says ADR training courses include Classes 2, 3, 4, 5, 6, 8 and 9, while some courses also include Class 1 explosives and Class 7 radioactive materials. For GS course selection, do not assume that seeing a class in this guide means it is included in a particular booking. Tell GS the class or UN number, whether the load is in packages or tanks, and whether you need initial or refresher training.

  • Packages: if the work involves dangerous goods in packages, compare the Core Packages option and confirm that it matches the goods and modules required for the work.
  • Tanks: if the work involves dangerous goods in tanks, compare the Core Packages and Tanks option and confirm the required modules before booking.
  • Classes 1 and 7: explosives and radioactive material are specialist classes. They are on request and are not included in the listed fixed-price packages; ask GS whether the relevant module can be arranged and request a separate written quote.

Current GS ADR course options and prices

GS lists Core Packages at £479 inc VAT per person and Core Packages and Tanks at £599 inc VAT per person. Classroom groups have a maximum of eight learners. View current ADR course prices and options.

Confirm the required class modules, examination inclusions, actual classroom venue, dates and written booking terms with GS before payment. This avoids choosing a course on the basis of a hazard-class name alone.

Use the class as a guide, not a substitute for the load information

The class gives a clear description of the hazard, but it is only one part of the transport information. Check the transport documentation and the requirements for the specific goods with the employer or consignor. For the official class descriptions, see the HSE classification guidance.

When you are ready to compare a GS option, start with the goods you expect to carry and whether they move in packages or tanks, then use the ADR training price and options page for the current advertised options.

For help selecting the relevant existing course, contact GS Driver Training.

Read the full article on GS Driver Training Blog.

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For more information about HGV training courses, call 01252 447808 or visit our courses page.