In the UN number system, how are materials categorized?

Materials in the UN number system are categorized based on their hazard characteristics. This system assigns a unique four-digit number to hazardous substances and articles to facilitate safe transportation and handling. The categorization takes into account various factors related to the danger posed by the materials, which can include flammability, toxicity, reactivity, and other potential hazards.

For example, materials that are explosive will have a different UN number than those that are corrosive or toxic. This classification helps first responders and handlers quickly identify the dangers associated with a particular substance, ensuring that proper precautions and procedures are followed to mitigate risks to health and safety during transportation, storage, and emergency response.

Other options related to weight, color, or availability do not play a role in the UN number classification system, as the focus is squarely on safety and hazard management.