Study the CDGP domain as a decision chain: classify the product from its own criteria data, select the governing provision and mode, package and mark it, write the transport document, and only then check quantity reliefs and segregation. Drill the chain on single products across road, sea, and air, citing a source for every determination, and let mode-by-mode conflicts — not volume of memorization — drive what you study next.
Hazard Class vs. Packing Group: Two Questions, Two Answers
A hazard class answers what kind of danger an article presents. A packing group ranks how severely a substance endangers packaging within certain classes. Treating them as interchangeable produces packaging and documentation answers you cannot defend.
Hazard classes and their divisions are fixed by the nature of the danger — flammability, corrosion, toxicity, reactivity, radioactivity — and the class does not shift with severity. Packing groups I, II, and III, denoting great, medium, and minor danger, exist only where the classification criteria define them, such as flammable liquids and certain toxic and corrosive substances. Two products can share a class yet carry different packing groups, and many articles carry no packing group at all. Packaging performance, some quantity thresholds, and certain modal restrictions key off the packing group rather than the class.
Work in two passes. Pass one assigns the class or division from the defining criteria. Pass two — only for classes that carry packing groups — ranks severity from property data such as flash point, skin corrosivity, or acute toxicity. In a simplified worked example, a liquid with a closed-cup flash point of 45 °C lands in class 3 and, on a generic criteria ladder, in packing group III; lower the flash point below 23 °C and the packing group tightens while the class stays put. Write both answers separately for every substance you study and label which question each one answers.
Shipping Name Selection: Exact Entries, Generic n.o.s. Entries, and Technical Names
Entry selection decides everything downstream: class, packing group, labels, and packaging assignments all hang off the list entry. Move deliberately from product description to the most specific applicable entry before touching packaging or paperwork.
Dangerous goods lists are organized so that every downstream requirement hangs off the entry you choose. Single entries cover precisely defined substances and articles; generic n.o.s. entries cover families that share hazard properties but not identity. The entry's row carries the class, packing group, labels, and packaging assignments, and special provisions attached to the entry can modify all of them. That is why entry selection comes first: settling on a looser generic entry before checking for a more specific match mislabels the whole determination.
Drill the movement from product description to entry. Take a product name, list its known properties, identify candidate entries, and eliminate the more general ones whenever a specific match holds. Whenever you land on an n.o.s. entry, note the technical name that must accompany it on the transport document — an n.o.s. entry without a technical name is an incomplete determination, not a stylistic preference. Time these lookups until the description-to-entry move takes seconds rather than minutes, and record why each rejected candidate failed.
One Product, Three Rulebooks: Drilling the Mode Conflict
The same package rarely tells the same story across road, sea, and air. Relief availability, marks, and documentation differ by mode, so an arrangement that complies at the dock can fail at the airport counter.
Study one product at a time across road, sea, and air, and keep a comparison note with a row per mode: packaging basis, marks, relief availability, document requirements. The rows rarely match, and that is the point. A relief provision may exist under one mode and not another; a designation such as marine pollutant primarily bites in sea transport; document names and formats differ. Conflicts between rows are where transport decisions actually live, and a note organized by product surfaces them faster than three separate regulation notebooks.
Worked scenario: drums of water-borne paint, class 3, packing group III in a simplified example, moving by sea and then completing the journey by air. The plausible mistake is carrying the sea-mode arrangement — its limited-quantity packaging logic and marks — straight onto the air leg because the classification did not change. The better decision is to treat the air leg as its own determination and re-verify quantity limits, packaging, marks, and documentation under air provisions. A package refused at acceptance means rework and a missed connection; the product never changed, the mode's demands did.
Relief Provisions: When Small Means Different Things in Different Places
Relief provisions — limited quantities and excepted quantities — swap full packaging and documentation duties for lighter, conditional ones, but only entry-by-entry and mode-by-mode. Verifying eligibility before touching packaging is the whole discipline here.
Relief provisions do not remove regulation; they trade full requirements for lighter ones. Limited quantities allow defined inner amounts in sturdy combination packaging with a distinctive mark; excepted quantities cover very small amounts under a packaging code of their own. Neither is automatic: eligibility reads entry-by-entry through the list columns and special provisions, and what a mode still demands in marks and documents varies. Verify eligibility before you touch packaging, because a relief claimed without entitlement is simply a non-compliant shipment.
Practice reliefs by re-running the same product three ways. Pack it at full quantity, then re-run the determination inside limited-quantity limits, then inside an excepted-quantity code, recording what changed in packaging, marks, and paperwork at each step. The table below turns that comparison into a decision aid. Expected observations: the classification never changes across the three runs, the marks do, and the documentation may shrink or not depending on the mode — differences worth being able to explain rather than memorize.
| Situation in your scenario | Provision to verify first | What changes downstream |
|---|---|---|
| Product at full quantity, no relief claimed | Standard packaging requirements for the class and packing group | Specification packaging, full hazard marks, complete transport document entry |
| Quantity within the entry's limited-quantity limits | Limited-quantity provision for each mode used | Combination packaging with inner limits, limited-quantity mark, documentation may be simplified depending on the mode |
| Very small inner quantities meeting an excepted-quantity code | Excepted-quantity provision and its packaging code | Packaging built to the code, excepted-quantity mark, reduced documentation in most modes |
| Product also meets environmentally hazardous criteria | Marine pollutant / environmentally hazardous substance designation | Additional mark for sea transport; check how each other mode treats the designation |
Documentation That Defends Itself
A transport document is defensible when every field traces to the same determination: entry, class, packing group, packaging, and marks tell one story. Technical names on generic entries and field-by-field consistency are the checkpoints.
Write the document from the determination notes, never from memory. The entry drives class and packing group; the packing instruction chosen drives the packaging description; the relief claimed drives the marks shown. Generic entries carry the technical name, and quantities must match what was actually packed. A defensible document is one where a reviewer can walk from any single field back to the criteria data or list row that produced it. That traceability is what a transport audit asks for, and it is the standard to hold your practice answers to.
Drill by repair: take a deliberately weak entry — 'Flammable liquid, n.o.s.' with no technical name and a packaging description that does not match the packing instruction you would actually use — and rebuild it field by field against your determination notes. Expected observations: in a deliberately weak entry, the class and packing group fields may still be correct, while technical names, packaging descriptions, and mark references drift. That drift pattern tells you where to slow down: at the fields that copy from decisions rather than from the product itself.
Segregation: The Check That Comes After Everything Else
Segregation is a between-packages question, not a per-package one. After every item in a shipment is classified, packaged, and documented, the final check asks whether those items may travel together at all.
Segregation asks a different question from everything before it: not whether each item is compliant alone, but whether these items may travel together. Modes publish segregation requirements between certain classes, and between classes and certain other cargoes, and the answer can differ by mode. Because each package in a consolidation can be fully compliant on its own, segregation is the one check with no earlier checkpoint — it only makes sense after classification, packaging, and documentation are settled for every item in the shipment.
Worked scenario: a consolidation carrying a class 5.1 oxidizer and the class 3 paint from earlier on one transport unit. The plausible mistake is treating segregation as satisfied because every item is individually documented and marked. The better decision is to run the segregation check for each mode on the journey before load planning, and to separate or re-stow where the requirement says so. This matters because combined compliance is a distinct question from individual compliance: adjacent incompatible goods can be refused before departure or, worse, behave differently in an incident than either would alone.
A Six-Week Practice Sequence with a Scoring Rubric
Build readiness by running the full decision chain on single products, week by week, until the chain is automatic. Score each finished scenario against a rubric so gaps in sourcing, consistency, and conflict-handling become visible.
Score every finished scenario on four axes, zero to two each: every determination cites a criteria paragraph or list entry; classification, packaging, marks, and document tell the same story; mode conflicts are flagged and resolved in writing; generic entries carry technical names and a rejected-candidate rationale. Eight points is a full score. Treat seven or above on three consecutive scenarios as the milestone that clears you to add a harder product family — a learning checkpoint for pacing your own study, not a prediction of any exam result.
For a practical exercise, run the full chain on three accessible products — a bleach concentrate, a solvent-borne paint, and an aerosol — and compare each result with the transport section of its safety data sheet. Expected observations: at least one data sheet will disagree with your criteria-based result or stay silent on a designation such as marine pollutant; resolving that disagreement against the transport criteria, in writing, is the point of the exercise. For administrative matters such as eligibility and scheduling, rely on the issuer at ihmm.org rather than on study notes.
- Week 1 — Criteria: classify ten substances with the two-pass habit, writing class and packing group as separate answers.
- Week 2 — Entries: timed description-to-entry lookups, with a recorded reason for each rejected candidate entry.
- Week 3 — Modes: rebuild the comparison note for five products across road, sea, and air, and flag every conflict in writing.
- Week 4 — Reliefs: re-run three products at full quantity, limited quantity, and excepted quantity, logging exactly what changed.
- Week 5 — Full chain: complete documentation and segregation for two multi-item consolidations.
- Week 6 — Timed chains: run the whole decision chain on new products under time pressure and score against the rubric.
References and further reading
Use these references to explore the concepts and check the latest information from the relevant organizations.