What is the difference between IATA, IMDG, 49 CFR and ADR?

They are the four major dangerous goods regulations, split by transport mode and geography. IATA DGR governs air transport worldwide, the IMDG Code governs sea transport worldwide, 49 CFR governs all modes within the United States, and ADR governs road transport across the European agreement countries. All four derive from the same UN Model Regulations, so the UN numbers, hazard classes and packing groups are shared, but the operational rules differ.

Which regulation applies to my shipment?

It depends on the mode and the route. Air freight follows the IATA DGR. Sea freight follows the IMDG Code. Road transport inside the US follows 49 CFR; road transport across European ADR countries follows ADR. A single multimodal door-to-door shipment can be governed by two or three of them in sequence, and you must satisfy each leg's rules.

Do all four use the same UN numbers?

Yes. All four regulations are built on the UN Recommendations on the Transport of Dangerous Goods (the 'Orange Book'), so UN numbers, proper shipping names, hazard classes and packing groups are common across them. What differs is the packing instructions, quantity limits, marking and labelling specifics, documentation and segregation rules.

Is IATA stricter than the others?

Generally yes for the same substance. Air transport is the least forgiving environment for a dangerous goods incident, so the IATA DGR tends to impose the tightest quantity limits, the most documentation and the most operator variations. Sea and road regimes are usually more permissive for the same UN number.

What about RID and ICAO TI?

RID is the rail equivalent of ADR in Europe and shares most of its structure. ICAO Technical Instructions are the intergovernmental source that the IATA DGR is built on; IATA adds operator and state variations on top. For most commercial shippers, IATA, IMDG, 49 CFR and ADR cover the practical cases.

IATA vs IMDG vs 49 CFR vs ADR: Which Regulation Applies?

IATA, IMDG, 49 CFR and ADR are the four major dangerous goods regulations, divided by mode and geography. The IATA Dangerous Goods Regulations govern air freight worldwide; the IMDG Code governs sea freight worldwide; 49 CFR governs transport within the United States; and ADR governs road transport across the European agreement countries. Which one applies depends on how and where your goods move — and a single door-to-door shipment can fall under two or three of them in sequence.

The good news: all four are built on the same foundation, so you are never starting from scratch when you cross from one to another.

The shared foundation

Every one of these regulations derives from the UN Recommendations on the Transport of Dangerous Goods — Model Regulations (the "Orange Book"), published every two years by the UN Committee of Experts. Because of that common root, the following are the same across all four:

UN numbers
Proper shipping names
The nine hazard classes and their divisions
Packing groups (I, II, III)

So classification — the work of finding the right UN number — transfers directly between modes. If you have not nailed that step yet, start with the UN number lookup and classification guide or the UN number lookup tool. What changes between regulations is everything downstream of the UN number.

What differs between them

For the same UN number, the four regimes diverge on the operational details:

Packing instructions and which packagings are permitted
Quantity limits per package and per transport unit
Marking, labelling and placarding specifics
Documentation — the Shipper's Declaration, transport document and waybill statements
Segregation rules between incompatible goods
Special provisions and modal exceptions

IATA DGR — air

The IATA Dangerous Goods Regulations govern goods moved by air, worldwide. They are built on the ICAO Technical Instructions and add airline operator variations and state variations on top. Air is the least forgiving environment for an incident, so IATA is generally the strictest regime for a given substance: the tightest quantity limits, the most documentation, and the most variations to check. The DGR is reissued annually. For the current cycle's changes see the IATA DGR edition changes for 2026, and for the document itself see how to read a Shipper's Declaration.

IMDG Code — sea

The International Maritime Dangerous Goods Code governs goods moved by sea, worldwide, under the SOLAS and MARPOL conventions. It is updated on a two-year amendment cycle. IMDG adds the concept of marine pollutants, container packing certificates, and a detailed segregation table for stowage aboard ship. It is generally more permissive than IATA for the same UN number. For the practical cheat sheet see the IMDG Code quick reference.

49 CFR — United States, all modes

Title 49 of the US Code of Federal Regulations, Parts 171–180, administered by PHMSA, governs hazardous materials transport within the United States across all modes. It largely harmonizes with the international rules for air and sea but carries its own domestic provisions, terminology ("hazardous materials" / "hazmat") and enforcement regime. Penalties are severe and inflation-adjusted annually — the statutory maximum runs into tens of thousands of dollars per violation per day. See the 49 CFR hazmat compliance checklist for the domestic specifics.

ADR — European road

The European Agreement concerning the International Carriage of Dangerous Goods by Road (ADR) governs road transport across its contracting parties. It introduces transport categories with per-transport-unit quantity thresholds, tunnel codes restricting which goods may pass through which tunnels, and orange-plate marking for vehicles. Its rail counterpart, RID, shares most of the same structure. For an introduction see the ADR beginner's guide.

Side-by-side summary

IATA DGR — Air, worldwide. Strictest. Annual edition. Shipper's Declaration, operator + state variations.
IMDG Code — Sea, worldwide. Marine pollutants, segregation table, container packing certificate. Two-year amendments.
49 CFR — United States, all modes. PHMSA enforcement, domestic provisions, steep inflation-adjusted penalties.
ADR — European road. Transport categories, tunnel codes, orange plates. RID is the rail twin.

One shipment, multiple rulebooks? Let the engine sort it.

DG Inspector takes a photo of your package and its SDS, finds the UN number, and applies the correct rules for the mode you select — air, sea or road — including the packing instruction, marks and documents for each leg.

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Which one applies to you — a decision aid

Moving by air? IATA DGR, anywhere in the world.
Moving by sea? IMDG Code, anywhere in the world.
Moving by road inside the US? 49 CFR.
Moving by road across European ADR countries? ADR (RID if by rail).
Multimodal door-to-door? Each leg follows its own regulation. Plan to the strictest leg so the package is acceptable end to end — usually the air leg if there is one.

The bottom line

Mode and geography decide the rulebook; the UN Model Regulations keep the classification constant across all of them. Find the UN number once, then apply the right regime — IATA for air, IMDG for sea, 49 CFR for the US, ADR for European road. A worked example across modes is the lithium battery, which carries the same four UN numbers everywhere but very different rules per mode — see are lithium batteries dangerous goods.