Foundations
Module 4 of 6 · Foundations

The nine classes — in everyday words

Class 1 explosives to Class 9 misc. — one familiar example each, plus the real placard.

ADR 2025 · 2.1 / 2.2
Friendly introduction & study aid. Not the official ADR certificate. The legal certificate comes from a DfT/SQA-approved training centre and the SQA exam.
Draft beginner content — pending review by a qualified DGSA

Lessons

Indigo · Lesson

Classes 1, 2, 3 — bangs, gases, flames

15s 1 · Explosive 2 · Gas 3 · Flammable liquid ADR 2025 · 2.2.1 / 2.2.2 / 2.2.3
ADR hazard class 1 — Explosive1 · Explosive
ADR hazard class 2 — Gas2 · Gas
ADR hazard class 3 — Flammable3 · Flammable liquid

Class 1 = explosives. Think fireworks, ammunition, blasting caps. They can go bang. Class 2 = gases. Think the LPG bottle on a BBQ, oxygen cylinders, the propane in a forklift. Pressurised, sometimes flammable, sometimes toxic. Class 3 = flammable liquids. Think petrol (UN1203), white spirit, paint thinner, methylated spirits. They can catch fire from a spark.

Class 1 = explosives (fireworks, ammunition).
Key points
  • Class 2 = gases (BBQ propane, oxygen cylinder).
  • Class 3 = flammable liquids (petrol, paint thinner).
ADR Citation
ADR 2025 · 2.2.1 / 2.2.2 / 2.2.3
ADR Part 2 defines class 1 (explosives), class 2 (gases) and class 3 (flammable liquids); each class has its own diamond label and classification criteria.
Draft content, pending DGSA review. Verify against the cited clause before relying on it.
Indigo · Lesson

Classes 4 and 5 — solids that burn, things that make others burn

20s 4.1 · Flammable solid 4.2 · Spontaneous 4.3 · Wet = danger ADR 2025 · 2.2.41 / 2.2.42 / 2.2.43 / 2.2.51 / 2.2.52
ADR hazard subclass 4.1 — Flam. solid4.1 · Flammable solid
ADR hazard subclass 4.2 — Flam. solid4.2 · Spontaneous
ADR hazard subclass 4.3 — Flam. solid4.3 · Wet = danger
ADR hazard subclass 5.1 — Oxidiser5.1 · Oxidiser
ADR hazard subclass 5.2 — Oxidiser5.2 · Organic peroxide

Class 4 = flammable solids and similar. Think matches (Class 4.1), oily rags that can catch fire on their own (4.2), or sodium that reacts with water (4.3). Class 5 = oxidisers. They aren't themselves on fire, but they make other things burn much harder — think swimming-pool chlorine tablets (5.1) or organic peroxides like in some glue hardeners (5.2). A spill of an oxidiser into a flammable liquid is a recipe for a serious fire.

Class 4 = flammable solids (matches, oily rags, water-reactive metals).
Key points
  • Class 5 = oxidisers (pool chlorine, peroxides).
  • Oxidisers don't burn themselves — they help others burn much harder.
ADR Citation
ADR 2025 · 2.2.41 / 2.2.42 / 2.2.43 / 2.2.51 / 2.2.52
Classes 4.1, 4.2, 4.3 cover flammable solids, spontaneously combustible substances and substances that emit flammable gases on contact with water; classes 5.1 and 5.2 cover oxidising substances and organic peroxides.
Draft content, pending DGSA review. Verify against the cited clause before relying on it.
Indigo · Lesson

Classes 6 and 7 — poisons and radioactivity

10s 6 · Toxic / infectious 7 · Radioactive ADR 2025 · 2.2.61 / 2.2.62 / 2.2.7
66 · Toxic / infectious
77 · Radioactive

Classes 6.1, 7 and 9 use illustrative placeholders until official artwork is supplied.

Class 6 = toxic and infectious. Think pesticides, cyanide, lab samples or medical specimens (6.1 toxic, 6.2 infectious). Class 7 = radioactive. Think medical isotopes for hospital scans, or industrial gauges. Class 7 is heavily regulated — even small quantities have strict packaging and paperwork rules.

Class 6.1 = toxic (pesticides, cyanide).
Key points
  • Class 6.2 = infectious (lab samples).
  • Class 7 = radioactive (medical isotopes, gauges).
ADR Citation
ADR 2025 · 2.2.61 / 2.2.62 / 2.2.7
Class 6.1 covers toxic substances, class 6.2 infectious substances; class 7 covers radioactive material and is governed by additional dedicated provisions in chapter 2.2.7.
Draft content, pending DGSA review. Verify against the cited clause before relying on it.
Indigo · Lesson

Classes 8 and 9 — corrosives and 'everything else dangerous'

15s 8 · Corrosive 9 · Miscellaneous ADR 2025 · 2.2.8 / 2.2.9
ADR hazard class 8 — Corrosive8 · Corrosive
99 · Miscellaneous

Classes 6.1, 7 and 9 use illustrative placeholders until official artwork is supplied.

Class 8 = corrosives. Think bleach concentrate, sulphuric acid (UN1830), strong cleaning fluids, car batteries. They eat skin, metal and other materials. Class 9 = miscellaneous — anything dangerous that doesn't fit the other classes. The famous example is lithium batteries (UN3480) — not flammable like petrol, not corrosive like acid, but they can short, overheat and catch fire if mishandled.

Class 8 = corrosive (bleach concentrate, sulphuric acid).
Key points
  • Class 9 = miscellaneous — anything dangerous not in 1–8.
  • Lithium batteries (UN3480) are the headline Class 9 example.
ADR Citation
ADR 2025 · 2.2.8 / 2.2.9
Class 8 covers corrosive substances (which attack skin and other materials); class 9 covers miscellaneous dangerous substances and articles, including environmentally hazardous substances and lithium batteries.
Draft content, pending DGSA review. Verify against the cited clause before relying on it.

Practice questions

0 / 5 answered
  1. 1
    Petrol is which class?
  2. 2
    Which class is for corrosive substances like sulphuric acid?
  3. 3
    A propane gas bottle for a BBQ belongs to which class?
  4. 4
    Lithium-ion batteries (UN3480) belong to which class?
  5. 5
    Fireworks belong to which class?
Practice quiz — pick an answer to see whether it's right and why.
Next: Packing group — 'how dangerous, exactly?'Go to ready check