For the CDGP, build your preparation around one repeated habit: for every consignment, first name the transport mode, then name the governing publication — UN Model Regulations as the base framework, ICAO Technical Instructions or IATA DGR for air, IMDG Code for sea — and only then trace the UN number through that text. Drill that decision chain until it is automatic, because classification, packing, marks, and documentation all hang off it.
Which Publication Governs: UN, ICAO/IATA, or IMDG
The transport mode determines the governing publication: the UN Model Regulations form the international base framework, the ICAO Technical Instructions (commonly applied through the IATA DGR) govern air, and the IMDG Code governs sea. Naming the governing text is always your first lookup.
The four publications share a common skeleton because the modal codes implement the UN Model Regulations. Classification criteria, UN numbering, and general structure carry across, which is why studying the base framework is efficient. But the base text is a reference point, not the operative compliance document for a completed movement: air and sea add mode-specific packing instructions, quantity limits, marks, and operational provisions that have no force in the other mode.
Build a one-page map showing how the chapters of your four books parallel each other, then stress-test it. Take one consignment and locate the same UN number entry in the air text and the sea text side by side, noting exactly where the wording, columns, or packing references diverge. Before drilling anything else, practice the selection step in isolation: read a short shipping scenario, state the mode aloud, and name the governing publication in one sentence. Every later step inherits this choice, so it must be a reflex rather than a deliberation.
| Context | Governing publication | Differences to check first |
|---|---|---|
| Air (passenger and cargo aircraft) | ICAO Technical Instructions; IATA DGR as the widely used field manual | Quantity limits by aircraft type, air-specific packing instructions, air-only restrictions on certain articles |
| Sea | IMDG Code | Stowage and segregation provisions, marine pollutant considerations, sea-specific emergency and operational content |
| Base framework | UN Model Regulations | Classification criteria, numbering, and overall structure — a reference point, not the operative text for a movement |
Classification Drives Everything: UN Numbers, Classes, Packing Groups
Every downstream decision — packing, marking, documentation — flows from classification: the UN number, proper shipping name, class or division, and packing group where assigned. If classification is wrong, no amount of careful packing or paperwork restores compliance.
Work from the dangerous goods list entry as your anchor. Compare the related concepts so they do not blur: the class or division describes the hazard type; the packing group, used for certain classes, grades the degree of danger within that hazard, with packing group I representing the greatest danger. These two scales are independent — a high class number does not mean low severity — and mixing up the two scales is a conceptual error worth fixing early.
Proper shipping name selection is its own skill. The regulations direct you to the entry that most precisely describes the substance, with generic entries reserved for goods that fit no specific description. Practice by taking five substances, writing the proper shipping name, class, and packing group from your own reasoning first, and only then opening the book to verify. Include at least one mixture and one article so you confront how the list handles them, not just single pure substances; the gap between your answer and the list entry shows exactly which selection rules you have not internalized.
Worked Scenario 1: Lithium Batteries Offered for Air Instead of Sea
Lithium batteries show why mode selection matters: air imposes restrictions with no sea equivalent, so a shipment plan built on sea experience can fail completely on air. Verify the air text before offering, not after a rejection.
Scenario: a forwarder has moved pallets of lithium-ion batteries shipped alone by sea for years, using the sea text's packing provisions. A customer now wants the next pallet to go by air. The plausible mistake is to treat this as a routing change only — same Class 9 handling, same packaging logic, same paperwork — and offer it under a plan copied from the sea routine.
The better decision is to open the air publication first. Lithium-ion batteries shipped alone are barred from carriage on passenger aircraft and are subject to air-specific packaging and condition requirements that simply do not appear in the sea text. Only after establishing what air permits should you also check the IMDG Code's treatment for comparison. Why it matters: the air text can forbid outright what sea allows, and the reverse comparison — knowing sea remains available — also shapes the customer conversation. Generalize the lesson: whenever the mode changes, re-derive the compliance picture from the new governing text rather than porting a packing plan across modes.
Worked Scenario 2: Limited Quantities and Excepted Quantities Are Not Interchangeable
Limited quantities and excepted quantities are two distinct relief regimes, each with its own package limits, conditions, and mark, and each mode applies them differently. Never assume one mode's small-volume relief transfers to another shipment or mode.
Scenario: a consignment of flammable liquid, packing group II, in small inner glass packagings is being quoted. The shipper, recalling a sea shipment of a similar product, applies the limited quantity approach with the limited quantities mark to the new air shipment without checking the air text. The mistake is treating relief as a property of the product rather than of the product-plus-mode-plus-quantity combination.
The better decision is to trace the substance's dangerous goods list entry in the air publication and read its limited quantity and excepted quantity columns directly, confirming the inner and outer packaging limits and any conditions. Then apply the correct mark for the regime actually used — the limited quantities diamond and the excepted quantities mark are different symbols signaling different regulatory bases. Why it matters: relief provisions are conditional, and marking a package under the wrong regime misstates the legal basis on which it is offered. A useful exercise: pick one UN entry and write out, side by side, how the air and sea texts treat it under both regimes.
Documentation and Package Communication: What Each Mode Expects
Transport documents, marks, and labels must match the governing publication. Air and sea declarations carry overlapping information but differ in layout, certifications, and additional statements, and package communication is checked element by element against the list entry.
Compare the two document families directly. The air shipper's declaration for dangerous goods and the declaration used for sea and multimodal movements share a core of information — UN number, proper shipping name, class or division, packing group, quantity and type of packaging — but they are not the same form, and requirements such as additional statements or the handling of limited and excepted quantity shipments differ. Practice by drafting both documents from scratch for one consignment and listing where their content diverges.
Package communication deserves the same treatment. For a given list entry, enumerate every required label, mark, and supplementary marking — including items such as orientation arrows and any marine pollutant considerations relevant to the sea text — and check each element against the entry rather than against memory. A practical exercise: audit three described packages against a checklist built from the list entry, and record any element you would have omitted. Each omission is a lookup habit to repair, not a fact to memorize harder.
A Timed Lookup Drill With a Self-Check Rubric
Because the CDGP is an open-book examination, lookup speed and accuracy are trainable skills in their own right. Run a timed drill tracing UN numbers through the publications, and score each trace against a rubric that checks every link in the chain.
The drill: select ten UN numbers spread across the classes, including at least two articles and one mixture. For each, record the dangerous goods list row, proper shipping name, class or division, packing group where assigned, the governing publication for both an air and a sea movement, the applicable packing instruction for each mode, all required labels and marks, and any air passenger-versus-cargo distinction. Time each trace, set your own target, and tighten it as you improve.
Score each trace out of eight: one point for the correct list row, one for class and packing group, two for the correct packing instruction in each mode, two for complete labels and marks, and two for identifying any air-only restriction. Interpret the pattern, not just the total: a step missed repeatedly signals a tabbing or indexing gap in that book, so fix the navigation — better tabs, a personal index of frequently used tables — rather than re-reading content. These scores are learning milestones for your own tracking, not predictions of any exam result.
- Correct dangerous goods list row located: 1 point
- Class or division and packing group correct: 1 point
- Correct packing instruction identified for each mode: 2 points
- Labels and marks complete and correct: 2 points
- Air-only restriction identified where applicable: 2 points
An Adaptable Preparation Sequence and Readiness Checks
Prepare in three passes: structure and navigation first, mode-difference comparisons second, and full consignment traces last. Readiness means you can move from mode to governing publication to a complete, compliant offer without assistance.
A realistic sequence you can compress or extend: first, map all four books, tab them, and learn the layout of the dangerous goods list and its columns. Second, run mode-difference comparisons for a set of UN numbers — air versus sea treatment, limited versus excepted quantities, the two declaration formats. Third, run full traces and mixed scenarios that force you to select the governing text before anything else. If you already work daily in one mode, spend proportionally more time on the modes you touch less often.
Check readiness against concrete evidence: you can name the governing publication for any described shipment in one sentence; you can trace any UN number to packing instruction, labels, and marks in both air and sea texts; you can distinguish limited from excepted quantities and state the correct mark; you can list the content elements of both declaration formats; and your timed drill consistently hits your target with full rubric points. One administrative note: examination format, permitted editions, fees, and scheduling are set by IHMM — confirm current details on the official IHMM CDGP page rather than relying on secondhand summaries.
Finally, use the IHMM examination blueprint as your allocation tool. The blueprint outlines the domains and tasks the examination draws from, so map your three passes onto those domains and let any thin areas — not habit or preference — decide where your remaining study hours go.
- Pass one: book structure, tabbing, and dangerous goods list navigation
- Pass two: mode-difference comparisons across a set of UN numbers and both document formats
- Pass three: full consignment traces and mixed scenarios under time pressure
- Ongoing: blueprint-driven allocation and readiness checks after each pass
References and further reading
Use these references to explore the concepts and check the latest information from the relevant organizations.