Classification & the Dangerous Goods List

Correct classification underpins everything else — get it wrong and the packaging, labels, documents and segregation all follow the wrong rule. The DGSA must be able to assign (or check) the class (1–9, with sub-divisions), the packing group (I/II/III where used), and the UN number and proper shipping name. For a mixture or a substance not named specifically, you work to the relevant 'N.O.S.' entry and apply the classification criteria in Part 2.

Nine classes; sub-divisions like 4.1/4.2/4.3, 5.1/5.2, 6.1/6.2.

ADR 3.2 Table A is the master lookup. Each UN entry is a row; the columns give the class, classification code, packing group, labels, special provisions, limited/excepted quantity allowances, packing instructions, tank codes and the tunnel restriction code. In the open-book exam the skill being tested is finding the right row and reading across the columns correctly — exactly what DGMind's UN lookup does, but the candidate must be able to do it from the book.

One row per UN entry; read ACROSS the columns for the full rule set.

Many real shipments are mixtures of substances, not a single named chemical. ADR has a layered rule: prefer the most specific entry that matches the predominant hazard. If a substance has more than one hazard, the precedence table (2.1.3.10) decides which class is primary; the others become subsidiary risks. If no specific name fits, use the generic / N.O.S. entry that matches the class and hazard (e.g. UN1993 'FLAMMABLE LIQUID, N.O.S.'), and on the transport document add the technical name(s) of the dominant constituents in brackets (3.1.2.8). Never pick an N.O.S. entry just because it's easier — specificity matters.

Prefer the most SPECIFIC entry that matches the goods (2.1.3).

For Class 3 the packing group is decided from flash point and initial boiling point, with specific cut-offs in 2.2.3.1. Packing group I covers liquids with very low flash point and low boiling point (most hazardous); II covers flash point < 23 °C with higher boiling point; III covers flash point 23–60 °C. Substances with flash point above 60 °C are not normally Class 3. The DGSA reviews the SDS values, applies the 2.2.3 criteria and verifies the assigned UN entry — wrong PG means wrong packaging and wrong threshold multiplier (1.1.3.6).

PG decided from flash point + initial boiling point (2.2.3.1).

Class 8 corrosives are assigned to PG I, II or III based on how quickly they cause irreversible damage to skin (or, where data exist, to metals). The 2.2.8.1.4 criteria use observation times (≤ 3 minutes, ≤ 60 minutes, ≤ 4 hours) for full-thickness destruction of intact skin. The DGSA checks the SDS supports the assigned PG; weak generic 'corrosive' descriptions without supporting data are a red flag. As with Class 3, wrong PG cascades into wrong packaging, threshold and sometimes wrong UN entry.

PG I: full-thickness skin destruction in ≤ 3 minutes.