Hazardous materials — explosive, flammable, toxic, corrosive, or radioactive — pose transport, handling and storage risks that require certified protective packaging. "UN" packaging refers to containers bearing the United Nations packaging symbol, certified by specialized international bodies; unauthorized packaging can be rejected outright at random inspections or at airports, and improper packaging risks both leakage and environmental harm, making UN boxes mandatory for hazardous-goods transport.
Typically multi-layered corrugated cardboard produced to specific standards, UN boxes offer three practical advantages: strong moisture resistance (particularly useful in humid regions/seasons and for preventing self-ignition of flammable solids exposed to water), good pressure resistance and sealing to prevent leakage and contamination in transit, and a lightweight construction that avoids adding unnecessary weight or volume — and cost — to a shipment.
UN boxes must come from qualified manufacturers holding third-party certification, and airlines or maritime authorities typically specify the exact box type required for their hazardous-goods shipments. For sea freight specifically, additional requirements apply: customs inspection, issuance of a Dangerous Goods Certificate, verification of the UN box's performance documentation, and maritime authority approval before the cargo can be loaded.
