mathematics

UN number

UN number is a mathematics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand UN number rather than just read about it. In short: A UN number (United Nations number) is a four-digit number that identifies hazardous materials, and articles (such as explosives, flammable liquids, oxidizers, toxic liquids, etc.) in the framework of international trade and transport. Some hazardous substances have their own UN numbers (e.g. acrylamide has UN 2074), while sometimes groups of chemicals or products with similar properties receive a common UN number (…

Key takeaways

UN number belongs to mathematics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect UN number to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of UN number from memory before moving on to harder problems.

Reference excerpt

A UN number (United Nations number) is a four-digit number that identifies hazardous materials, and articles (such as explosives, flammable liquids, oxidizers, toxic liquids, etc.) in the framework of international trade and transport. Some hazardous substances have their own UN numbers (e.g. acrylamide has UN 2074), while sometimes groups of chemicals or products with similar properties receive a common UN number (e.g. flammable liquids, not otherwise specified, have UN 1993). A chemical in its solid state may receive a different UN number than the liquid phase if its hazardous properties differ significantly; substances with different levels of purity (or concentration in solution) may also receive different UN number.

Hazard identifiers Associated with each UN number is a hazard identifier, which encodes the general hazard class and subdivision (and, in the case of explosives, their compatibility group). If a substance poses several dangers, then subsidiary risk identifiers may be specified. It is not possible to deduce the hazard class(es) of a substance from its UN number: they have to be looked up in a table.

Range UN numbers range from UN 0004 to about UN 3550 (UN 0001 – UN 0003 are no longer in use) and 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-dangerous substances.

Non-UN identifiers An NA number (North America number) is issued by the United States Department of Transportation and is identical to UN numbers, except that some substances without a UN number may have an NA number. These additional NA numbers use the range NA 9000 - NA 9279. There are some exceptions, for example, NA 2212 is all asbestos with UN 2212 limited to asbestos, amphibole amosite, tremolite, actinolite, anthophyllite, or crocidolite. Another exception, NA 3334, is self-defense spray, non-pressurized while UN 3334 is aviation-regulated liquid, not otherwise specified. For the complete list, see NA/UN exceptions. An ID number is a third type of identification number used for hazardous substances being offered for air transport. Substances with an ID number are associated with proper shipping names recognized by the ICAO Technical Instructions. ID 8000, Consumer commodity does not have a UN or NA number, and is classed as a Class 9 hazardous material.

See also Globally Harmonized System of Classification and Labelling of Chemicals – International standard managed by the United Nations Lists of UN numbers Dangerous goods – Substances harmful to people, property or the environment CAS Registry Number – Chemical identifier List of NA numbers

References

External links United Nations Committee of Experts on the Transport of Dangerous Goods UN Recommendations on the Transport of Dangerous Goods. Part 2 defines the hazard classes and their divisions and Part 3 contains a complete list of all UN numbers and their hazard identifiers. The Emergency Response Guidebook from the U.S. Department of Transportation contains a list of all assigned NA numbers along with recommended emergency procedures.

Illustrations

Worked examples

Example 1 — a first encounter with UN number

Start with the simplest possible case. Write down what UN number claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In mathematics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to UN number before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about UN number ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of UN number

In research: UN number appears in mathematics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses UN number in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: UN number is common in secondary-school and first-year university syllabi. It links to neighbouring topics Chemical numbering schemes, Lists of UN numbers, so understanding it makes those chapters shorter.
In everyday life: Look for UN number outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study UN number in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what UN number means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain UN number out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is UN number in simple terms?

Why does UN number matter?

Because it connects several mathematics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study UN number?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on UN number.