The basis of all national and international regulations for the safe transport of dangerous goods are the Recommendations ("Specification") of the "UN Committee of Experts" as published in "The Orange Book".
There are five different (relevant) Modal Authorities who each publish their own regulation manuals in which they follow "The Orange Book". These are the:
Goods which are classified as dangerous for transport range from those which are highly dangerous (such as explosives and fuming acids) to everyday products such as paints, solvents and pesticides found in the home and at work. Dangerous goods, which can also be called "Hazardous Materials" (mainly in the US), may be substances or products. The transport of such goods is regulated to ensure the safety of life, of the ship, aircraft or vehicle, and of other goods (such as foodstuffs) being transported. For example, solvents must be in sealed airtight containers otherwise the fumes could affect people in the close vicinity. Other substances may not be harmful unless they come into contact with fire or water, but for safety purposes these are also classified as dangerous goods.
When transporting "Hazardous Materials", in most cases, the packaging has to be certified to UN standards. The international agreements for the carriage of dangerous goods require packaging to be of a design-type certified by a national competent authority. This involves testing the packaging against the appropriate UN specification to ensure its suitability for the carriage of certain dangerous goods. Such packaging is often referred to as "type-approved", "UN Approved" or "UN certified" and marked in a particular way, prefixed by the UN logo and followed by codes.

(Click here to learn more about the UN Certification Process)
The U.N. marking system indicates several characteristics of the packaging, as well as information on the test levels the packaging has successfully passed. Because these test levels are related to the hazard level and physical and chemical characteristics of the substance to be filled, the markings also indicate some of the properties of the materials that may be packed in each container.
A sample UN Marking: 1H2 / Y1.8 / 100 / 06 / F / OA30900
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| UN | The United Nations Coding System | |||
| 1 |
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| H |
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| 2 |
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| Y |
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| 1.8 | Density or specific gravity of material packed OR For packaging intended for Solids (powders, pills, capsules, tablets) or that have inner packaging, this marking will indicate the maximum gross mass (weight) in kilograms. |
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| 100 | Hydraulic pressure in kilo-pascal (kPa) OR For packaging intended for Solids or that have inner packaging, an "S" in upper case will follow the gross mass. |
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| 06 | Current year | |||
| F | Country where container was manufactured | |||
| OA30900 | Code for manufacturing plant | |||