UN numbers and dangerous goods classes for chemical buyers

The first freight quotation for a chemical often comes back with a surcharge, a refusal, or a question about the UN number. That number decides how the cargo can move, and it is usually sitting in the safety data sheet you already have.

The UN number identifies the substance, not the product

A UN number is a four-digit code from the UN Model Regulations that identifies a hazardous substance or a group of substances with similar hazard. It is not a brand, a grade or a catalogue number. The same chemical from two suppliers carries the same UN number, and two grades of the same family can carry different ones.

Ask your supplier for the UN number in writing and check that it matches section 14 of the SDS. A mismatch between the SDS and the shipping documents is a customs problem waiting to happen.

Class and packing group

The class describes the type of hazard: flammable liquids, oxidising substances, toxic substances, corrosives and so on. The packing group describes the severity within that class, from I (great danger) to III (minor danger).

Packing group drives packaging cost and choice: a group I corrosive may need a different drum or inner packaging than the same product at group III. It also drives how much can go into one package and one container.

Section 14 of the SDS is where transport information lives

Section 14 of a 16-section SDS carries the UN number, proper shipping name, class, packing group, environmental hazards and special precautions for transport. If section 14 is blank or copied from another product, the document is not usable for booking freight.

Read it together with section 9, physical and chemical properties. A flash point that puts a liquid into a flammable class has to be consistent across those two sections.

Why the same chemical can ship two ways

Classification depends on concentration and form. A dilute solution may not be classified while the pure substance is, and a solid may escape a class that catches the same material as a powder. Packaging and quantity also change what is permitted.

This is why a supplier saying we have shipped it for years is not an answer. Ask what exactly was shipped, at what concentration, in what packaging, on what route.

Questions to settle before you book freight

• What is the UN number, class and packing group on the current SDS?
• Is the product shipped as a hazardous or non-hazardous cargo, and on what basis?
• Does the packaging carry the required UN specification marking?
• Are there quantity limits per package or per container for this class?
• Which documents does the forwarder need, and who issues them?

Getting these five answers before you request a rate saves a week of back and forth after the booking.