A packing group — the official ADR term — classifies a dangerous substance by the severity of the hazard it presents within its hazard class, not by the type of container it travels in. Three levels apply across most ADR dangerous goods: Packing Group I (high danger), Packing Group II (medium danger), and Packing Group III (low danger). The packing group is a mandatory field on every ADR transport document and sets the packaging construction standard the consignment must meet before it moves.
What Do the Three Packing Groups Mean?
Packing Group I, Packing Group II, and Packing Group III rate the degree of danger a substance presents within its hazard class — two Class 3 flammable liquids can sit at different packing group levels depending on how extreme their flash point and boiling point are.
Packing Group I
Packing Group I marks the highest danger within the class. Only UN Performance Level X packaging is authorised — containers tested to the most demanding drop, stacking, and leakproofness standards in the UN packaging approval system. Most PG I entries in ADR Table A carry no limited quantity exemption, or carry the most restrictive LQ inner packaging limits for that UN number.
Diethyl ether (UN 1155, Class 3, initial boiling point 34.6°C) and concentrated nitric acid (UN 1831, Class 8) are PG I substances that move regularly on European road freight lanes.
Packing Group II
Packing Group II covers the majority of industrial chemicals, solvents, and chemical intermediates in European road freight. UN Performance Level Y packaging is required — certified for PG II and PG III goods, tested to intermediate construction standards.
Petrol (UN 1203, Class 3), acetone (UN 1090, Class 3), isopropanol (UN 1219, Class 3), and hydrochloric acid (UN 1789, Class 8) all fall at PG II.
Packing Group III
Packing Group III identifies the lowest danger level within the class. UN Performance Level Z packaging is permitted — the least demanding certified standard, approved for PG III goods only.
Diesel fuel (UN 1202, Class 3), white spirit (UN 1300, Class 3), and many diluted cleaning products within Class 8 sit at PG III. PG III substances qualify most readily for limited quantity exemptions at standard commercial package sizes.
The ADR 2025 classification criteria connecting flash point thresholds, boiling point ranges, and corrosion rates to each packing level form part of the dangerous goods framework documented in the Go Trans logistics glossary.
Which ADR Hazard Classes Use Packing Groups?
Classes 3, 4.1, 4.2, 4.3, 5.1, 6.1, 8, and most of Class 9 assign packing groups — Classes 1, 2, 5.2, 6.2, and 7 do not.
The eight classes using packing groups span the most common dangerous goods categories in European road freight: flammable liquids (Class 3), flammable solids (Class 4.1), substances liable to spontaneous combustion (Class 4.2), water-reactive substances (Class 4.3), oxidising substances (Class 5.1), toxic substances (Class 6.1), corrosives (Class 8), and miscellaneous dangerous substances including lithium batteries (Class 9).
Classes 1, 2, 5.2, 6.2, and 7 classify substances through their own internal systems. Class 1 uses compatibility groups and division numbers (1.1 through 1.6). Class 2 uses hazard type codes — 2.1 (flammable gas), 2.2 (non-flammable non-toxic gas), and 2.3 (toxic gas). Class 5.2 uses sub-type letters A through G based on thermal stability. Class 6.2 uses categories 6.2A and 6.2B. Class 7 follows IAEA activity-based categories independent of the packing group system.
A blank packing group field on a transport document for any substance in these five classes is a correct, compliant entry — not an incomplete document and not a sign of a low-hazard substance. A Class 2 aerosol and a Class 1 explosive can both present severe danger. The packing group system governs neither.
How Is a Packing Group Determined?
Packing group assignment follows class-specific physical property criteria in ADR 2025. For Class 3 flammable liquids, flash point and initial boiling point at standard pressure set the level:
Class 3 Flammable Liquids
- PG I — initial boiling point at or below 35°C at standard pressure, regardless of flash point. Diethyl ether (UN 1155) has an initial boiling point of 34.6°C and falls at PG I.
- PG II — flash point below 23°C with an initial boiling point above 35°C. Petrol (UN 1203) has a flash point below −40°C and a boiling point well above 35°C. Acetone (UN 1090) has a flash point of −20°C.
- PG III — flash point at or above 23°C and at or below 60°C. Diesel fuel (UN 1202) has a flash point in the range of 55–65°C depending on grade. Heating oils with a flash point above 60°C and at or below 100°C are assigned PG III under a specific ADR provision for certain petroleum fractions.
Class 8 Corrosive Substances
For Class 8 corrosives, the rate of full-thickness skin tissue destruction on contact determines the level:
- PG I — full-thickness destruction within 3 minutes of contact. Concentrated sulphuric acid (UN 1831) falls here.
- PG II — full-thickness destruction in more than 3 minutes but within 1 hour.
- PG III — full-thickness destruction in more than 1 hour but within 4 hours, or corrosion of steel or aluminium at more than 6.25 mm per year at 55°C.
Where a substance carries a subsidiary hazard that produces a stricter packing group than the primary hazard, the stricter level governs the consignment — packaging standards, documentation requirements, and labelling all apply at the higher packing group.
Where Does the Packing Group Appear on ADR Documents?
The packing group is the fourth mandatory field in the complete dangerous goods description on the ADR transport document, placed directly after the hazard class: UN number + proper shipping name + hazard class + packing group. A diesel fuel consignment reads "UN 1202, GAS OIL, 3, III." A petrol consignment reads "UN 1203, PETROL, 3, II." A missing or incorrect packing group makes the transport document non-compliant under ADR Annex A.
The UN number and the packing group are the two paired classification fields on every ADR transport document — together they connect the consignment to its full compliance profile in ADR Table A, covering packaging instructions, limited quantity thresholds, tunnel restriction category, and emergency response procedures.
The complete set of shipping documents in European road freight — transport document, written instructions, Safety Data Sheet, and vehicle approval certificate — must be present on every ADR consignment from collection to delivery.
The UN packaging approval mark on certified containers carries a letter code showing the performance level the packaging has passed:
- X covers PG I, II, and III goods.
- Y covers PG II and III only.
- Z covers PG III only.
Shipping a PG I substance in Y- or Z-marked packaging is non-compliant under ADR regardless of whether the container physically retains the goods without leaking.
How Does a Shipper Find the Correct Packing Group?
ADR Table A in ADR 2025 is the definitive European road freight reference — every classified substance has a row showing its packing group alongside the UN number, hazard class, and all applicable transport conditions. ADR 2025 is freely accessible through the UNECE website.
Safety Data Sheet Section 14 (Transport Information) is the practical starting point. The manufacturer or supplier states the packing group there alongside the UN number, proper shipping name, and hazard class. When the SDS is current and correctly prepared, the complete dangerous goods description for the transport document is ready before the shipper opens ADR Table A.
For flammable liquid mixtures, the packing group is determined by flash point and boiling point tests conducted on the prepared mixture — not on its individual components. A mixture's test results can produce a different packing group from any single ingredient. Classification must be confirmed by testing before the booking is placed.
The ADR transport regulation sets the classification criteria for every hazard class. Packing group assignment runs alongside UN number identification and hazard class confirmation as part of the complete dangerous goods description a consignor prepares before the transport document is issued.
How Does Go Trans Handle Packing Group Requirements for ADR Shipments?
Go Trans arranges shipping hazardous goods across Europe through its carrier network, matching each consignment's UN number, hazard class, and packing group to the right ADR-certified carrier on the lane. Shippers booking ADR freight through Go Trans provide the complete dangerous goods description at the point of booking — UN number, proper shipping name, hazard class, and packing group.
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