UN Class 3 Flammable Liquids: Packaging, Labeling and Shipping Guide
Everything a shipper needs about Class 3: definition thresholds, packing group assignment, hazard label, package marking, and modal rules under IMDG, IATA DGR, and ADR.
UN Class 3 in the UN Model Regulations on the Transport of Dangerous Goods (the "Orange Book") covers flammable liquids. It is one of the largest classes by shipment volume — gasoline, ethanol, paints, adhesives, resins, and countless solvents all fall here.
Definition: What Makes a Liquid "Class 3"?
Per UN Model Regulations Chapter 2.3, a flammable liquid is a liquid, or a liquid containing solids in solution or suspension, with a flash point of not more than 60°C (closed-cup test), OR any liquid offered for transport at temperatures at or above its flash point.
Also included: liquids offered for transport at temperatures at or above 100°C, in a liquid state, and which give off flammable vapor at temperatures ≤ that carriage temperature (these are "elevated-temperature" flammable liquids, UN 3256).
Exclusions:
- Liquids with flash point > 60°C are not Class 3 (they may fall under Class 9 UN 3082 environmentally hazardous, or be non-regulated).
- Alcoholic beverages of ≤ 24% ABV are unregulated.
- Certain viscous liquids (e.g., paints of PG III) may benefit from viscosity exemption (special provision 640) if solvent separation is negligible.
Packing Groups (PG I, II, III)
| Packing Group | Flash point (closed cup) | Initial boiling point | Danger level |
|---|---|---|---|
| PG I | — | ≤ 35°C | High |
| PG II | < 23°C | > 35°C | Medium |
| PG III | ≥ 23°C and ≤ 60°C | > 35°C | Low |
Packing group determines packaging quality, allowed quantity limits per package, tank type, and stowage.
Common UN Numbers in Class 3
| UN No. | Proper Shipping Name | Typical PG |
|---|---|---|
| UN 1090 | Acetone | II |
| UN 1170 | Ethanol / Ethanol solution | II or III |
| UN 1173 | Ethyl acetate | II |
| UN 1203 | Motor spirit / Gasoline / Petrol | II |
| UN 1219 | Isopropanol | II |
| UN 1230 | Methanol | II |
| UN 1263 | Paint / Paint-related material | I, II, or III |
| UN 1866 | Resin solution | I, II, or III |
| UN 1993 | Flammable liquid, n.o.s. | I, II, or III |
| UN 3256 | Elevated temperature liquid, flammable, n.o.s. | III |
| UN 3475 | Ethanol and gasoline mixture (E10, E85 etc.) | II |
Class 3 Hazard Label
The label is a diamond-shaped placard/label:
- Background: red.
- Symbol: flame, in black or white, in the upper half.
- Class number "3": in the lower corner.
- Minimum size (package label): 100 × 100 mm (may be reduced to 50 × 50 mm on very small packages).
- Placard size (transport unit): 250 × 250 mm minimum.
Package Marking
In addition to the hazard label, each package must display:
- UN number preceded by "UN" (e.g., "UN 1170").
- Proper Shipping Name (PSN) — the exact name from the UN Dangerous Goods List. Do not use a trade name.
- UN packaging code molded/stamped on the packaging (e.g., "1A1/Y1.4/150/25/USA/XYZ" for a steel drum).
- Orientation arrows for combination packagings containing liquids > 5 L (except IBCs and drums with certain closures).
- Limited Quantity mark or Excepted Quantity mark if shipped under those exemptions.
Modal Differences: IMDG vs IATA vs ADR
Sea Transport — IMDG Code
Sets stowage categories (typically Category B/E), segregation from oxidizers and Class 5.1, and EmS emergency schedules (F-E for fire, S-E/S-D for spillage). Requires ship-specific documentation and CTU packing certificates for containers.
Air Transport — IATA DGR
Most restrictive. Passenger aircraft: PG I generally forbidden; PG II limited (typically 1 L per package on passenger, 60 L cargo); PG III up to 60 L passenger, 220 L cargo. Always check Table 4.2 for the specific UN number. Fiber-drum outers not allowed for many Class 3 entries.
Road Transport in Europe — ADR
Tunnel restriction codes apply (e.g., PG I typically "D/E" — restricted in tunnels of category D and E). Vehicle placarding front and rear, orange plates with hazard identification number (33 for highly flammable, 30 for flammable) above UN number.
Documentation Required
- Dangerous Goods Declaration (DGD) or Shipper's Declaration.
- Safety Data Sheet (SDS) — Section 14 must match.
- Container Packing Certificate (CPC) for sea freight in containers.
- Air Waybill with Class 3 endorsement for air.
- Emergency response information (e.g., ERG guide reference for road/rail in North America).
Common Compliance Failures
- Using a trade name instead of the Proper Shipping Name.
- Wrong packing group — forgetting that PG depends on both flash point AND initial boiling point, not flash point alone.
- Missing orientation arrows on inner receptacles.
- Non-UN certified packaging — you must use packaging tested to the packing group level (X = PG I/II/III, Y = PG II/III, Z = PG III only).
- Overfilling — Class 3 packagings must not be filled beyond 98% at 55°C to allow for thermal expansion.
- Ignoring the 60°C flashpoint threshold — high-flash-point solvents (>60°C) are not Class 3 but may still be Class 9 for aquatic toxicity.
References
This article is based on the following primary sources; always check the edition in force before shipping or labelling.
Related Tools
- UN Dangerous Goods Search — lookup UN number, PSN, class, PG.
- GHS Label Generator — supply-side label complement.
- SDS Template — Section 14 transport information.
- GHS Pictogram Pack
Sources: UN Model Regulations on the Transport of Dangerous Goods, 23rd revised edition (2023); IMDG Code Amendment 41-22; IATA DGR 65th edition (2024); ADR 2025.