DOT Packing Groups
A packing group is a Roman numeral, I, II or III, that shows the degree of danger of a hazardous material within its DOT hazard class. Packing group I is the greatest danger, II is medium and III is minor. The packing group decides how strong the shipping container must be.
| Packing group | Degree of danger | What it means for packaging |
|---|---|---|
| PG I | Great danger | The most hazardous materials within a class. Packaging must meet the highest performance standard (marked X). |
| PG II | Medium danger | Moderate hazard. Packaging must meet at least the Y performance standard. |
| PG III | Minor danger | The least hazardous within the class. Packaging can meet the Z standard. |
Which hazard classes use packing groups
Packing groups apply to most, but not all, classes. They are assigned using criteria specific to each class, so a PG II flammable liquid and a PG II corrosive are not comparable.
- Class 3: Flammable and Combustible Liquids
- Division 4.1: Flammable Solids
- Division 4.2: Spontaneously Combustible Materials
- Division 4.3: Dangerous When Wet
- Division 5.1: Oxidizers
- Division 6.1: Toxic Substances
- Class 8: Corrosive Materials
These do not use packing groups:
- Class 1: Explosives
- Class 2: Gases
- Division 5.2: Organic Peroxides
- Division 6.2: Infectious Substances
- Class 7: Radioactive Materials
Class 9 uses packing groups for only some entries.
How the packing group is set
- Class 3 flammable liquids: by flash point and initial boiling point. PG I has an initial boiling point of 35 °C (95 °F) or less; PG II has a flash point below 23 °C (73 °F) and a boiling point above 35 °C; PG III has a flash point from 23 °C up to and including 60 °C (140 °F).
- Class 8 corrosives: by how quickly the material destroys skin, or how fast it corrodes steel or aluminum. Shorter times mean a more severe group.
- Division 6.1 toxic materials: by oral, dermal and inhalation toxicity data, such as LD50 and LC50.
- Divisions 4.2, 4.3 and 5.1: by how readily the material self-heats, reacts with water, or accelerates burning in standard tests.
When a material meets the criteria for more than one hazard, the regulations set the order of precedence and the packing group of the primary hazard. The final answer is always the entry in the Hazardous Materials Table in 49 CFR 172.101.
Packing groups and UN performance markings
UN-specification packagings are tested for the packing group they may carry. The marking on a drum or box includes a letter that shows the highest packing group it is approved for: X for groups I, II and III, Y for groups II and III, and Z for group III only. A package marked Y cannot be used for a PG I material.
Where to find it on an SDS
The packing group is in Section 14: Transport information, next to the UN number, proper shipping name and hazard class. If it says “not applicable” or “none”, the material is either not regulated for transport or its class does not use packing groups. For the glossary definition, see packing group.
Packing groups versus GHS categories
Packing groups and GHS hazard categories are different systems. PG I roughly resembles the most severe GHS categories, but the cut-offs differ. Do not convert between them.
Frequently asked questions
What is a packing group?
A packing group is a Roman numeral (I, II or III) that shows how dangerous a hazardous material is within its DOT hazard class. PG I is the greatest danger, PG II is medium and PG III is minor.
Do all hazard classes have packing groups?
No. Classes 1, 2 and 7, and Division 6.2, do not use packing groups. Packing groups apply to Class 3, Divisions 4.1 to 4.3, Division 5.1, Division 6.1, Class 8 and some Class 9 materials.
Is PG I always more hazardous than PG III?
Yes, within the same hazard class. Packing groups are not comparable across classes, because the criteria are different for each class.
Where do I find the packing group on an SDS?
In Section 14 (Transport information), next to the UN number, proper shipping name and hazard class.