When reading a label, what does a four-digit UN number provide?

• A. The hazard class
• B. The quantity in the shipment
• C. The date of manufacture
• D. The UN number uniquely identifies the substance or material in international transport

Answer: (D)

The four-digit UN number on a label is a unique identifier for the material being transported internationally. This code ties to a specific substance or material, so responders and shippers know exactly what they’re dealing with and can access the correct safety data and handling requirements. It doesn’t indicate how much is in the shipment or when it was manufactured, and while hazard class information appears on labels or placards, the UN number itself is about identifying the substance, not its quantity or manufacture date.