In which section of the Emergency Response Guidebook would a firefighter look if they know the chemical ID number of a hazardous material?

The correct answer is the yellow section. Firefighters utilize the Emergency Response Guidebook (ERG) to quickly find critical information about hazardous materials. When a chemical ID number is known, the yellow section of the ERG is specifically designed for use with numerical listings. Each entry corresponds to a specific material and provides vital information, including the material's name, potential hazards, and initial response and safety measures.

In contrast, the blue section is organized alphabetically by material name, which would be less efficient if only the chemical ID number is available. The red section refers to a list of chemical names that start with numbers, and the green section contains information on specific response actions for certain types of incidents but is not suitable for looking up a chemical based solely on its ID number. Thus, the yellow section is the most appropriate and efficient choice for identifying hazardous materials when their chemical ID number is known.