Packing Groups I, II, and III, Explained
Updated 2026-07-25 · DGM One
A packing group answers one question: how dangerous, within its class?It’s a small field on the declaration that drives packaging, quantity limits, and a surprising number of rejections.
The three packing groups
| Packing group | Degree of danger |
|---|---|
| Packing Group I | Great danger |
| Packing Group II | Medium danger |
| Packing Group III | Minor danger |
The packing group is assigned using the classification criteria of the substance’s hazard class, for example, flash point and boiling point for flammable liquids, or, for corrosives, exposure time and observation period on skin, and corrosion rate on steel or aluminium. It is not chosen by preference; it follows from the properties of the material.
Not every class uses a packing group
Packing groups apply to most classes, but not all. Under the UN Model Regulations, the IATA DGR, the IMDG Code and ADR, they are not assigned to several classes and divisions, including:
- Class 1, explosives (danger is expressed through division and compatibility group)
- Class 2, gases
- Division 4.1, self reactive substances
- Division 5.2, organic peroxides
- Division 6.2, infectious substances (UN 3291 clinical waste is the exception)
- Class 7, radioactive material
For the classes that do use them, the packing group can differ by the specific substance and even by concentration, which is why reading it straight from the applicable table matters. A number of individual articles carry no packing group at all regardless of class, UN 3480 lithium ion batteries among them, so always check the entry itself rather than assume from the class. 49 CFR’s own Hazardous Materials Table does not always follow this, and it shows a packing group against some entries in these classes, so confirm there directly for US ground shipments.
Where the packing group comes from
You’ll find the assigned packing group alongside the UN number and proper shipping name in the dangerous goods list for your mode, the Hazardous Materials Table under 49 CFR, the Dangerous Goods List in the IMDG Code, or the List of Dangerous Goods in the IATA DGR. When a substance is shipped in solution or mixture, the packing group can shift, so the entry you start from must match the material you actually have.
Common mistakes
- Carrying over a packing group from a similar sounding entry instead of the exact one.
- Assigning a packing group to a class that doesn’t use one.
- Missing a concentration dependent shift between PG II and PG III.
Editorial note: this page is for orientation only. Always assign the packing group from the current regulation for your mode. DGenius reads it from the correct entry and shows the citation.
Questions shippers ask
What do packing groups mean?
Packing groups indicate the degree of danger a substance presents within its hazard class: Packing Group I is great danger, Packing Group II is medium danger, and Packing Group III is minor danger. They drive packaging performance requirements and, in many cases, quantity limits.
Do all dangerous goods have a packing group?
No. Under the UN Model Regulations, IATA, IMDG and ADR, packing groups are not assigned to several classes and divisions, including explosives (Class 1), gases (Class 2), self reactive substances of Division 4.1, organic peroxides (Division 5.2), infectious substances (Division 6.2, apart from UN 3291 clinical waste, which carries packing group II) and radioactive material (Class 7); their danger is expressed through other means. Many individual articles, lithium batteries among them, carry no packing group at all, whatever their class.
