Which of the following is NOT listed as an on-scene warning sign in a terrorist event involving chemical or biological agents?

• A. Unexplained vapor clouds, mist, and plumes
• B. Recognizable odors and/or taste
• C. Unexplained patterns of illnesses or death
• D. Refueling equipment on scene

Answer: (D)

On-scene warning signs come from what you observe indicating a possible release of a chemical or biological agent. The most direct signals are physical or sensory clues that something is dispersing into the environment: visible vapor clouds, mist, or plumes show that a substance is spreading in the air. Recognizable odors or tastes can alert you that a hazardous agent is present, though not all agents have a strong scent or taste, so these cues aren’t foolproof. Unexplained patterns of illness or death among people at the scene also point to exposure, especially when symptoms cluster or appear suddenly in a way that doesn’t fit a typical medical event.

Refueling equipment on scene, however, is not a warning sign of a chemical or biological release. It’s a logistical activity that could occur in many different kinds of incidents and doesn’t by itself indicate that a hazardous agent has been released.