UN Number Law and Legal Definition
UN number is a four-digit number assigned to hazardous material in the framework of international transport. It is required for highway transportation, water and air transit. UN number is used to help designate the emergency response procedure in the event of a spill or release. Some hazardous substances like acrylamide (UN2074) have their own UN numbers, while sometimes groups of chemicals or products with similar properties receive a common UN number. For example, flammable liquid-UN1993.