A UN Number is a four-digit identifier. UN1170 (ethanol), UN1230 (methanol), UN1789 (hydrochloric acid), UN1830 (sulphuric acid), assigned by the United Nations to every hazardous substance regulated for international transport. The list is maintained by the UN Sub-Committee of Experts on the Transport of Dangerous Goods and reissued every two years as the UN Recommendations (the “Orange Book”).
Where the UN number must appear
For any DG shipment, the same UN number must appear in five places:
- DG Declaration (signed shipper’s document)
- MSDS Section 14 (transport information)
- Package marking, printed or stencilled on every drum, IBC, pail
- Container placard, the diamond-shaped placards on each side of the container
- Shipping documents, bill of lading, manifest, customs filings
If the same UN number does not appear identically in all five places, the carrier will reject the booking or, worse, will load the cargo and the destination port will reject it on arrival.
UN vs NA numbers
UN numbers are international, recognised under the IMDG Code, the IATA Dangerous Goods Regulations, and the various national rail and road regulations. NA numbers are North America-specific identifiers used by the US Department of Transportation for substances that are regulated for transport in North America but do not have an international UN number. For sea freight from China, you will only ever use UN numbers. NA numbers come into play in some North American truck and rail movements at the destination side.
Looking up a UN number
The authoritative source is the IMDG Code itself, which is updated every two years and cross-references UN numbers with proper shipping names, hazard classes, packing groups, and special provisions. ECHA (in the EU) and the US Pipeline and Hazardous Materials Safety Administration (PHMSA) maintain searchable UN number databases. Most factory MSDS documents will have the UN number in Section 14, but verify against the official source rather than trusting the factory’s MSDS for a substance you are about to ship.
Common UN number errors
- Generic vs specific. Some UN numbers are generic (e.g. UN1993 “Flammable liquid, n.o.s.”, not otherwise specified) and require a technical name in the proper shipping name. Some are specific (UN1170 ethanol). Using the generic UN number when a specific one exists is a misdeclaration.
- Solution vs neat substance. A solution of a substance often has a different UN number than the neat substance. Example: hydrochloric acid neat (UN1789) and hydrochloric acid in aqueous solution (UN1789 with concentration on the documents). Sulphuric acid, on the other hand, has different UN numbers depending on concentration and whether it is fuming.
- Multi-component formulations. A formulated product containing several hazardous substances may have a different UN number than any of its individual components. The factory must determine the formulation’s UN number based on the dominant hazard, not just pick one component.
Practical sourcing notes
Before a DG container loads, we cross-check the UN number on the DG Declaration against Section 14 of the MSDS, the drum labels (we receive label proofs from the factory before production), and the container placards (we get photographs from the inspector before sailing). Five-place agreement. DG Declaration, MSDS, drum labels, placards, manifest, is the only acceptable state. Any disagreement is fixed at the factory before the booking goes to the carrier.
NA numbers and the US-only variant
US Department of Transportation regulations sometimes use NA-prefixed identifiers (NA9290, NA9295, etc.) for substances that do not have a UN number under the IMDG Code but are classified as hazardous under US 49 CFR 172.101. NA numbers apply to US domestic transport and to import declarations into the US. For Chinese cargo bound for the US, the IMDG-classified UN number governs sea transport while the NA number (if applicable) governs the US-domestic onward leg from the port of arrival to the receiver site. Most chemical exports from China use UN numbers throughout because they are IMDG-regulated; NA numbers appear in a small set of US-specific classifications.
UN number lookup and the standard sources
For substances commonly shipped from China, the authoritative sources for UN number assignment are the IMDG Code itself (Volume 2, Chapter 3.2 dangerous goods list) and the UN Recommendations on the Transport of Dangerous Goods Model Regulations (Orange Book). The factory’s MSDS Section 14 should reference the assigned UN number, but the buyer should independently verify the UN number against the IMDG Code if any ambiguity exists. The Chinese-language equivalent is the GB 12268-2024 (Chinese national standard for dangerous goods classification), which mirrors the IMDG list. A factory citing only the GB 12268 reference without the corresponding UN number is providing incomplete documentation; insist on the UN number explicitly.
Related terms
IMDG is the parent code. DG Declaration carries the UN number on the shipper’s signed document. Packing Group is the second piece of information that travels with the UN number on every DG shipment.