UN vs. NA Numbers: Regional Variations

Comparison of international UN numbers and North American NA numbers used to identify hazardous materials in transport, highlighting when and why NA numbers are assigned and how they differ in scope and application.

The identification of hazardous materials in transport relies on standardized numeric codes called UN numbers (United Nations numbers) for global consistency. In North America—specifically the United States and Canada—an additional numbering scheme, known as NA numbers (North American numbers), is used in some cases where an entry is required for domestic ground transport but no international UN number exists. Understanding the relationship, differences, and proper use of UN and NA numbers is essential for shippers, carriers, warehouse operators, and emergency responders to maintain compliance, ensure safe handling, and enable effective incident response.

How the two systems relate

Most NA numbers are identical to the corresponding UN number when the substance already has an international designation. The reason for this alignment is to preserve interoperability between domestic shipments in North America and international transport regimes. When a hazardous substance is widely recognized and listed in international regulations, that four-digit UN number is used consistently in the U.S., Canada, and globally.

Why NA numbers exist

NA numbers were created to fill a practical gap: some hazardous substances may be regulated for ground transport within the United States and Canada before, or instead of, receiving a UN number from international bodies. In those cases, regulators in North America assign an NA number so that the material has an authoritative identifier for labeling, documentation, and emergency response on domestic roads and rail. NA numbers are therefore a regional supplement, not a replacement for UN numbers.

Typical differences and patterns

• Identity: When both exist for the same substance, the NA number and the UN number will generally be identical.
• Regional-only entries: If a substance is regulated domestically but lacks an international designation, it receives an NA number. These are commonly assigned within specific number ranges; practitioners often note that many region-specific NA entries start with digits 8 or 9.
• Scope of acceptance: UN numbers are accepted worldwide in international transport regulations (maritime IMDG Code, air ICAO-TI, ADR/RID in Europe, etc.). NA numbers are valid for transport within the U.S. and Canada only, and are not recognized for international shipments outside those jurisdictions.

Regulatory context and who issues the numbers

UN numbers are part of the global framework developed by the United Nations Committee of Experts on the Transport of Dangerous Goods and are incorporated into international modal regulations (e.g., IMDG, ICAO). NA numbers are designated by competent authorities in North America—primarily the U.S. Department of Transportation (DOT) and Transport Canada—and appear in national/regional regulations and guidance documents for ground transport.

When to use UN vs. NA numbers

• Use the UN number for any international shipment or whenever the substance is listed under international regulations.
• Use the NA number for domestic road or rail shipments within the U.S. and Canada only when no UN number exists or when the applicable North American regulations require an NA designation.
• When both a UN and NA number exist and are identical, the numbering is interchangeable; however, always follow the specific marking and documentation requirements of the jurisdiction and mode of transport.

Practical implications for operations

Using the correct identifier affects labeling, placarding, shipping papers, emergency response documentation, and carrier acceptance. A shipment using an NA number cannot be assumed acceptable for international transport unless the receiving party confirms equivalence with an internationally recognized UN entry. Conversely, consignments carrying a UN number are broadly recognized for international movement but still must meet any additional domestic requirements for packaging, quantity limits, and route restrictions.

How to determine which number applies

1. Consult the Safety Data Sheet (SDS) and the manufacturer or supplier for the recommended shipping name and regulatory identification.
2. Check the U.S. DOT and Transport Canada dangerous goods lists and regulations for NA numbers and domestic classifications.
3. Check international lists (UN Model Regulations, IMDG, ICAO) to see if a UN number exists for the substance or a close equivalent.
4. If uncertain, contact the competent authority, a qualified dangerous goods consultant, or the carrier's dangerous goods specialist for guidance.

Best practices

• Maintain up-to-date regulatory references for both international and North American lists so staff can quickly identify the correct designation for each mode and destination.
• Document decision logic in standard operating procedures (SOPs): how to choose UN vs. NA numbers, who is authorized to make the determination, and how to record the choice.
• Train frontline staff—warehouse handlers, drivers, and shipping clerks—on the differences in scope and the practical consequences for transport and documentation.
• When preparing multi-modal shipments, verify that the identifier used is acceptable for every mode involved (road, rail, sea, air) and for any border crossings on the route.

Common mistakes and pitfalls

• Assuming an NA number is valid outside the U.S. and Canada — this can lead to customs delays, rejection by carriers, and safety compliance issues abroad.
• Failing to confirm whether a UN number exists — using an NA number when a UN number is available can create inconsistencies in international documentation.
• Relying solely on historical paperwork — regulatory lists are updated periodically; ensure your references reflect current editions.

Conclusion

UN and NA numbers together provide a practical framework for identifying hazardous materials in transport. UN numbers deliver international consistency, while NA numbers allow North American regulators to address region-specific needs for ground transport. Correct use depends on scope—domestic versus international—accurate classification, and adherence to the regulatory requirements of the mode and jurisdiction involved. For safe, compliant logistics operations, keep regulatory lists current, document classification decisions, and train staff to distinguish when a UN number or an NA number is the appropriate identifier.