Hazard Class 3 — Flammable Liquids
Fuels, solvents, paints and adhesives — classification by flash point and initial boiling point.
Overview
Class 3 covers liquids that emit a flammable vapour at or below a defined temperature. Classification depends on flash point and initial boiling point, and the packing group (I, II or III) reflects the severity of the hazard — PG I is the most hazardous.
Class 3 is one of the most common classes in aviation MRO because it covers fuels for ground-support equipment, paints, primers, sealants, cleaning solvents and many adhesives.
Aviation context
The most frequent classification mistake in MRO is treating a paint or sealant as 'just a paint' rather than checking Section 14 of the SDS. A two-component sealant with a flash point below 60 °C may be a fully regulated Class 3 PG III product, and shipping it as non-DG is a serious undeclared-dangerous-goods event.
Excepted Quantities (EQ) and Limited Quantities (LQ) often apply to small Class 3 shipments, but the EQ / LQ provisions still require correct marking and packaging — they are not a free pass to ship undeclared.
Typical UN numbers in aviation MRO
| UN Number | Proper Shipping Name | Notes |
|---|---|---|
| UN1133 | Adhesives (3, PG II or III) | Many MRO adhesives and primers |
| UN1263 | Paint / Paint related material (3, PG I, II or III) | Topcoats, primers, thinners |
| UN1170 | Ethanol or Ethanol solutions (3) | Cleaning agents, calibration fluids |
| UN1993 | Flammable liquid, n.o.s. (3, PG I, II or III) | Common 'not otherwise specified' entry |
Packaging and marking essentials
- Packing instructions depend on the packing group and on whether the shipment is on passenger or cargo aircraft (e.g. PI353 / PI355 / PI361 / PI364 — verify against the current IATA DGR edition).
- Inner packagings must be compatible with the liquid, and absorbent material is required for many entries.
- Mark the package with the UN number, proper shipping name, flame hazard label and orientation arrows where applicable.
Frequently Asked Questions
Is jet fuel a Class 3 dangerous good?
Yes. Aviation kerosene (Jet A, Jet A-1) is classified as UN1863 Fuel, aviation, turbine engine in Class 3. It is rarely shipped as cargo by air, but the classification matters when shipping samples or contaminated containers.
How do I know the packing group of a paint?
Read Section 14 of the SDS. If only Section 9 is available, use the flash point and initial boiling point thresholds defined in the UN Model Regulations to assign PG I, II or III — but this should be done by a trained DG specialist, not estimated.
Do Limited Quantities still require a DGD?
Shipments fully compliant with the Limited Quantity provisions for the specific entry can be exempt from the full DGD requirement, but they must carry the LQ mark and remain within strict net-quantity limits per inner and outer package.
Need to classify a specific part?
DG Copilot identifies the UN number, hazard class and air transport status from a part number — in seconds.
Other hazard classes
This information is provided for guidance only. Always verify against the current IATA DGR edition. Final classification and DGD must be validated by a certified DG specialist.