What standard identifies the necessary way to label hazardous materials using a four-digit UN number?

The standard that identifies the necessary way to label hazardous materials using a four-digit UN number is the yellow-bordered section. This section is specifically designed to provide immediate recognition of hazardous materials by using the United Nations (UN) numbers, which are critical for first responders and hazardous materials personnel. The UN number serves as a unique identifier for specific substances and their potential hazards, facilitating prompt and effective response during emergencies.

This system enhances safety by ensuring that responders can quickly ascertain the nature of the material they are dealing with, which is vital for determining the appropriate response procedures. In practice, the yellow border signifies key information regarding the material, allowing for a clear understanding of its classification and potential risks. Knowing how to interpret these labels is an essential part of HAZMAT operations training, as it directly affects the safety of first responders and the environment.