UN Numbers (United Nations Numbers)

UN Numbers are four-digit codes assigned by the United Nations Committee of Experts on the Transport of Dangerous Goods. Each number identifies a specific hazardous substance or article, or a group of similar substances, for the purposes of international transport regulation. There are currently over 3,500 UN Numbers in use, ranging from UN0004 (ammonium picrate, an explosive) to UN3549 (medical waste). These codes appear on shipping documents, package labels, and vehicle placards whenever hazardous materials move by ocean, air, truck, or rail.

How UN Numbers Work in Practice

Each UN Number is tied to a set of specific transport requirements. The number itself tells carriers, handlers, and emergency responders what they are dealing with. For example, UN1203 is gasoline, UN1993 covers flammable liquids not otherwise specified (N.O.S.), and UN3481 identifies lithium-ion batteries packed with or contained in equipment. Knowing the UN Number allows a carrier to look up the substance’s hazard class, packing group, allowable packaging types, quantity limits, labeling requirements, and any special provisions that apply.

The codes are published in the UN Recommendations on the Transport of Dangerous Goods, often called the “Orange Book,” which serves as the foundation for national and modal regulations worldwide. In the United States, the Department of Transportation incorporates UN Numbers into 49 CFR (Code of Federal Regulations) Parts 100 through 185. The International Maritime Dangerous Goods (IMDG) Code uses them for ocean shipments. The International Air Transport Association (IATA) Dangerous Goods Regulations reference them for air cargo.

Hazard Classes and Packing Groups

Every UN Number is assigned to one of nine hazard classes: explosives (Class 1), gases (Class 2), flammable liquids (Class 3), flammable solids (Class 4), oxidizing substances (Class 5), toxic and infectious substances (Class 6), radioactive material (Class 7), corrosives (Class 8), and miscellaneous dangerous goods (Class 9). Many UN Numbers also carry a packing group designation (I, II, or III) indicating the degree of danger, with Packing Group I representing the highest risk.

A single substance can have different transport requirements depending on its concentration, physical state, or packaging configuration. Hydrogen peroxide, for instance, is assigned UN2014 at concentrations above 60%, UN2984 between 20% and 60%, and is not regulated below 8% concentration. Getting the correct UN Number for the specific formulation being shipped is the first step in compliance.

E-Commerce and UN Numbers

Online sellers encounter UN Numbers most frequently with lithium batteries (UN3480 for standalone batteries, UN3481 for batteries in equipment), aerosol products (UN1950), perfumes and alcohol-based cosmetics (UN1266), nail polish and remover (UN1263), and various cleaning chemicals. Amazon’s hazmat review process requires sellers to provide Safety Data Sheets (SDS) for any product that may contain hazardous materials. The SDS includes the applicable UN Number, which Amazon uses to determine whether the product can be stored in FBA fulfillment centers and under what conditions.

Products classified under certain UN Numbers face storage restrictions, special packaging requirements, or outright exclusion from FBA. Lithium battery products, for example, must pass Amazon’s hazmat review and may be limited to specific fulfillment center locations equipped to handle them. Sellers who fail to disclose a product’s hazmat classification risk having their inventory suspended or destroyed, along with potential account-level penalties.

Shipping Documentation

When hazardous goods ship domestically by ground, the bill of lading must include the UN Number, proper shipping name, hazard class, packing group, and quantity. For ocean freight, the dangerous goods declaration references the UN Number along with the IMDG Code requirements. For air freight, the shipper’s declaration for dangerous goods follows IATA formats with the UN Number prominently displayed. Freight forwarders and carriers that handle these shipments verify the documentation against the actual cargo before accepting it. Prep centers like MeisterPrep that handle products with UN Number classifications coordinate with carriers to ensure proper documentation and packaging before outbound shipment, preventing rejection at the carrier terminal or, worse, regulatory fines during a DOT roadside inspection.