UN numbers are four-digits that identify hazardous substances such as explosives, flammable liquids, toxic substances, etc., in the framework of international transport. UN numbers are also known as UN IDs.
Example: UN1202 - Gas Oil / Diesel Fuel / Heating Oil (light)
UN1202 falls under Class 3 Flammable hazard classificatoins.
Transportation of dangerous goods (hazardous materials) in Canada by road is normally a provincial jurisdiction. The federal government has jurisdiction over air, most marine, and most rail transport. The federal government acting centrally created the federal transportation of dangerous goods act and regulations, which provinces adopted in whole or in part via provincial transportation of dangerous goods legislation. The result is that all provinces use the federal regulations as their standard within their province; some small variances can exist because of provincial legislation. Creation of the federal regulations was coordinated by Transport Canada. Hazard classifications, such as Class 3 listed above, are based upon the UN Model.
A chemical in its solid state may receive a different UN number than the liquid phase if their hazardous properties differ significantly; substances with different levels of purity (or concentration in solution) may also receive different UN numbers.
UN numbers range from UN0001 to about UN3500. They are assigned by the United Nations Committee of Experts on the Transport of Dangerous Goods. They are published as part of their Recommendations on the Transport of Dangerous Goods, also known as the Orange Book. These recommendations are adopted by the regulatory organization responsible for the different modes of transport.
There is no UN number allocated to non-hazardous substances. These will simply not have a UN number.