Foundations
Module 5 of 6 · Foundations

Packing group — 'how dangerous, exactly?'

PG I = very dangerous, PG II = medium, PG III = a bit. A simple way to grade danger within a class.

ADR 2025 · 2.1.1.3
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

Amber · Lesson

Three levels of danger

20s ADR 2025 · 2.1.1.3

Within a hazard class, products are graded by how dangerous they are. There are three levels — called Packing Groups: PG I = very dangerous (e.g. a highly volatile flammable liquid that ignites at very low temperatures). PG II = medium. PG III = lower danger (still regulated, but milder). Think of it like chilli heat: I is killer hot, II is medium, III is mild. Petrol (UN1203) is PG II. Diesel oil (UN1202) is PG III.

PG I = high danger.
Key points
  • PG II = medium danger.
  • PG III = lower danger (still regulated).
ADR Citation
ADR 2025 · 2.1.1.3
Substances are assigned to packing group I, II or III according to the degree of danger they present (high, medium, low respectively).
Draft content, pending DGSA review. Verify against the cited clause before relying on it.
Amber · Lesson

Why packing group matters in practice

15s ADR 2025 · 4.1.1.3

Why care? Because the packing group affects how strong the packaging must be, and sometimes affects how much you can carry under simpler rules. Stronger packaging for PG I; lighter packaging for PG III. So a worker shouldn't move a PG I substance in a PG III container — the container isn't built for it.

PG affects packaging strength rules.
Key points
  • PG I needs the strongest packaging; PG III the lightest.
  • Also affects some quantity-exemption thresholds.
ADR Citation
ADR 2025 · 4.1.1.3
Packagings used for dangerous goods must meet a performance level corresponding to the packing group assigned (X, Y, or Z for PG I, II, III).
Draft content, pending DGSA review. Verify against the cited clause before relying on it.
Amber · Lesson

Not every class uses packing groups

10s ADR 2025 · 2.1.1.3

Heads up — not every class uses packing groups. Class 1 (explosives), Class 2 (gases), Class 5.2 (organic peroxides), Class 6.2 (infectious substances) and Class 7 (radioactive) are managed differently. So if you're reading paperwork for a gas cylinder and the PG box is blank, that's normal — not a missing field.

Classes 1, 2, 5.2, 6.2 and 7 don't use packing groups.
Key points
  • Blank PG for a gas or explosive is normal — not an error.
ADR Citation
ADR 2025 · 2.1.1.3
Packing groups apply to many but not all classes — class 1, 2, 5.2, 6.2 and 7 are assigned by different criteria and do not use packing groups.
Draft content, pending DGSA review. Verify against the cited clause before relying on it.

Practice questions

0 / 4 answered
  1. 1
    What does PG I mean?
  2. 2
    Why does packing group matter?
  3. 3
    Which class does NOT use packing groups?
  4. 4
    A transport document for a gas cylinder has a blank PG column. What is this?
Practice quiz — pick an answer to see whether it's right and why.
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