Final Answer:
In the Emergency Response Guidebook, information is primarily referenced based on DOT hazard placards. It serves as a quick reference for emergency responders during incidents involving hazardous materials in transportation. The answer is D. DOT hazard placards.
Step-by-step explanation:
The Emergency Response Guidebook (ERG) primarily references information found on DOT hazard placards.
The ERG is a guidebook used by emergency responders, including firefighters, police, and other personnel, to quickly identify and respond to incidents involving hazardous materials during the initial phase of a transportation incident. It provides information based on the DOT (Department of Transportation) hazard placards that are displayed on vehicles transporting hazardous materials.
While other sources such as chemical labels, NFPA 704 placards, and safety data sheets are valuable in providing information about hazardous materials, the ERG specifically focuses on DOT hazard placards for quick reference during emergency situations.