Reference

The Three Regulatory Frameworks Behind Every Shipment

Ground, air, and sea each have their own dangerous-goods rulebook. Here's what 49 CFR, the IATA DGR, and the IMDG Code each cover — and how to tell which one applies to you.

Hazardous materials shipping is governed by overlapping regulatory frameworks. A single shipment crossing borders or changing modes of transport may be subject to all three of the frameworks below — simultaneously. Misclassifying a material, or applying the wrong rulebook for the mode, can mean civil penalties, criminal liability, or a catastrophic incident.

All three frameworks share one foundation: the UN Recommendations on the Transport of Dangerous Goods (the "Orange Book"), which defines the 9 hazard classes, UN numbers, and packing groups. Each rulebook then layers its own mode-specific provisions on top — which is why the same UN number can carry different quantity limits or packaging rules depending on how it moves.

Ground · United States

49 CFR — the U.S. backbone

Title 49 of the Code of Federal Regulations, Subchapter C (Parts 171–180), is administered by the Pipeline and Hazardous Materials Safety Administration (PHMSA). It defines the Hazardous Materials Table (49 CFR §172.101), which assigns proper shipping names, hazard classes, identification numbers, packing groups, and labeling and placarding requirements for every regulated material moving by highway or rail in the United States.

Compliance is not optional. Shippers, carriers, and consignees each bear distinct responsibilities, and PHMSA enforces civil penalties up to roughly $96,624 per violation per day, with criminal penalties for willful violations. The §172.101 table is the data source behind every UN page on this site.

Air · International

IATA DGR — the standard for air

The IATA Dangerous Goods Regulations are updated annually and incorporate the ICAO Technical Instructions, which carry treaty force under the Chicago Convention. Air shipments face stricter quantity limits, packaging requirements, and documentation than ground — for good reason. A leak at 35,000 feet has nowhere to vent.

Lithium battery shipments in particular have driven significant DGR revisions over the last decade following multiple in-flight incidents. If any leg of your shipment flies, the DGR governs that leg regardless of how it traveled before.

Sea · International

IMDG Code — maritime transport

Adopted by the International Maritime Organization (IMO), the IMDG Code is mandatory under the SOLAS Convention for vessels carrying dangerous goods at sea. It harmonizes with the UN Orange Book but adds maritime-specific provisions: stowage and segregation requirements, marine pollutant designations, and limits on what may be carried aboard passenger vessels.

Segregation rules — which dangerous goods may not be stowed near one another — are far more detailed at sea than on the road, because a vessel can be days from the nearest port.

First response

The ERG — the bridge to the field

The Emergency Response Guidebook (ERG), updated every four years by PHMSA in cooperation with Transport Canada and Mexico's SICT, links the regulatory world to the operational one. It is not a shipping regulation — it is a first-response tool.

When responders arrive at an incident, they do not have time to consult 49 CFR. They look up the UN number on a placard or shipping paper, find the assigned ERG guide number (a three-digit number from 111 to 174 in the 2024 edition), and follow the standardized initial actions for that guide. Every UN page on this site surfaces that guide number so you can put it on your shipping papers and response plans before anything goes wrong. See the ERG guide reference and evacuation distances for more.

Which one applies to you? Follow the mode. Ground in the U.S. → 49 CFR. Air → IATA DGR. Sea → IMDG Code. An intermodal shipment must satisfy the rules for every mode it touches, and air and sea are almost always stricter than ground.
FAQ

Common questions

What is the difference between 49 CFR, the IATA DGR, and the IMDG Code?
They govern different modes. 49 CFR covers U.S. highway and rail (PHMSA). The IATA DGR covers air worldwide. The IMDG Code covers ocean transport under SOLAS. A shipment that changes modes can be subject to more than one.
Which framework applies to my shipment?
Follow the mode of transport. Ground in the U.S. → 49 CFR. Anything flown → IATA DGR. Anything by sea → IMDG Code. Intermodal shipments must comply with every mode they touch, and air and sea rules are generally stricter than ground.
Are all three based on the same UN system?
Yes — all three build on the UN Recommendations on the Transport of Dangerous Goods (the Orange Book), which defines the 9 hazard classes, UN numbers, and packing groups. Each adds its own mode-specific rules on top.
How does the ERG fit in?
The Emergency Response Guidebook isn't a shipping regulation — it's the first-response bridge. Responders read the UN number off a placard or shipping paper, find the ERG guide number, and follow the standardized actions for that guide.

UNLookup is a reference utility. This page summarizes how the three frameworks relate but is not a substitute for current editions of 49 CFR, the IATA DGR, the IMDG Code, or the Emergency Response Guidebook. Always verify against the official source applicable to your mode of transport before tendering a shipment. Regulations change; this page is updated periodically and may not reflect the most recent amendments.