Decoding the UN Number and Proper Shipping Name (PSN) — Hazmat classification

The UN Number is a four‑digit identifier assigned to hazardous substances and articles; the Proper Shipping Name (PSN) is the standardized label required on transport paperwork and packaging to describe that substance for safe movement.

Overview

UN Numbers and Proper Shipping Names (PSNs) form the foundational shorthand of hazardous materials transport. A UN Number is a four‑digit numerical code (for example, UN 1203 = Gasoline) assigned by the United Nations Sub‑Committee of Experts on the Transport of Dangerous Goods to identify a substance or a group of substances with similar hazards. The PSN is the standardized English name that must appear on transport documents, labels, and often on packages themselves. Together they communicate, in a consistent and globally recognized way, the identity and basic hazard class of the material being moved.

Why they matter

UN Numbers and PSNs enable regulators, carriers, emergency responders, and handlers to quickly determine the risks and required controls for a shipment. They determine applicable packaging, labeling, placarding, segregation, stowage, handling, and documentation requirements. Because many chemicals have multiple common or trade names, the UN/PSN system provides a single authoritative reference that reduces ambiguity and prevents dangerous misclassification or miscommunication during transport.

How the UN number and PSN are assigned

Assignment begins with hazard evaluation. A competent authority or expert applies international classification criteria (examples include the UN Model Regulations, ICAO/IATA DGR for air, IMDG for sea, and regional rules for road/rail) to determine which hazard class(es) apply. If a substance matches a listed entry in the relevant regulations, that entry provides both the UN Number and the PSN. If no exact match exists, a generic or generic chemical group entry and a corresponding UN Number may apply. For mixtures, classification often follows decision trees and testing to determine whether the mixture is covered by an existing entry or should be assigned a generic entry.

Where the PSN appears

The Proper Shipping Name must be used in transport documentation (shipping papers, air waybills, multimodal bills), on the transport unit manifest, and on package markings where required. The PSN is often accompanied by subsidiary information such as the hazard class (e.g., Class 3 flammable liquid), packing group (I, II, or III), net quantity, and, when required, additional information like the technical name in parentheses for mixtures or the statement “marine pollutant.” Labels and placards display hazard class and UN Number (on placards or orange panels for road transport) but typically do not show the full PSN; the PSN remains essential on the paperwork and package marking.

Practical example

Gasoline is a widely recognized example: the UN Number UN 1203 identifies gasoline and related fuels. The Proper Shipping Name is GASOLINE. For a hazmat shipment of gasoline by road, shipping papers would read: "UN 1203, GASOLINE, 3, PG II" (where 3 is the hazard class for flammable liquids, and PG II indicates a packing group). The same identifier and PSN are used across modes with mode‑specific additional requirements applied by air, sea, or road rules.

Mixtures and technical names

When a mixture does not exactly match a listed UN entry, shippers may need to use a generic entry and include a technical name in parentheses after the PSN to clarify the specific composition (for example, "UN 1993, FLAMMABLE LIQUID, N.O.S. (contains x% of solvent Y)"). Section 14 of the Safety Data Sheet commonly contains the UN Number and transport classification information; this is frequently relied upon by shippers and 3PLs, though responsibility for correct classification remains with the shipper or manufacturer.

Key operational impacts

Accurate use of UN Numbers and PSNs affects carrier acceptance, insurance, emergency response, and regulatory compliance. Misdeclared or undeclared hazardous materials can lead to shipment refusals, costly fines, delays, contamination or damage, and safety incidents. For example, many regulators impose heavy penalties for undeclared hazardous goods; carriers may impose their own sanctions for noncompliance. Emergency responders use the UN Number and PSN to look up response guidance in resources such as the Emergency Response Guidebook (ERG).

Best practices for shippers and logistics operators

• Maintain up‑to‑date classification records and SDSs that include Section 14 transport data.
• Use the UN Model Regulations and mode‑specific regulations (IATA/ICAO, IMDG, ADR/ RID) as authoritative references when preparing shipping documents.
• Include the correct PSN, UN Number, hazard class, packing group, and any required technical name on paperwork and markings.
• When using generic entries or N.O.S. descriptions, add the technical name to aid emergency response and carrier handling.
• Establish quality checks — either manual review or automated validation — to confirm that the UN Number on the SDS matches the shipping papers and carrier manifest mapping.
• Provide employee training on recognizing and applying UN Numbers and PSNs across modes, including updates to regulatory lists.

Common pitfalls

Frequent mistakes include relying solely on an SDS without independent verification, using obsolete PSNs or UN Numbers (regulatory lists are updated periodically), failing to include required technical names for mixtures, and mismatching the UN Number and PSN on paperwork. Another common error is using a trade or brand name instead of the PSN on shipping documents — this can render the shipment noncompliant and dangerous in an emergency.

Conclusion

For anyone involved in moving hazardous goods, proficiency with UN Numbers and Proper Shipping Names is essential. They serve as the lingua franca for hazards in transport and are central to safe, compliant operations. Systems, processes, and training that prioritize accurate assignment and consistent use of UN Numbers and PSNs reduce risk, improve carrier acceptance, and protect people, assets, and the environment.