IATA Packing and Shipping Dangerous Goods Practice Test 2026 - Free Dangerous Goods Packing and Shipping Practice Questions and Study Guide

UN numbers are four-digit identifiers assigned to hazardous substances and articles to name the exact material in transport. This unique code ties to the approved shipping name and its hazards, so anyone handling or responding to an incident can quickly know what material is involved and what actions are required. The UN number stays constant across modes and regions, enabling consistent labeling, documentation, and regulatory compliance, and it directs responders to the correct emergency guidance and safety information. The other options refer to weight, packaging, or route details, which don’t identify a specific dangerous substance and thus don’t provide the essential, material-specific information needed for safe handling and effective emergency response.