What provides the basis for the hazard and risk assessment that determines the risk-based response?

• A. Decontamination
• B. Size up
• C. PPE selection
• D. Evacuation

Answer: (B)

Starting with a thorough scene size-up is essential because it gathers the real-time information about the hazard, potential exposures, ambient conditions, and the incident’s scope that the risk-based decision relies on. This initial assessment forms the foundation for evaluating hazard and risk, allowing responders to decide what protective actions are necessary, what level of containment is required, and what resources must be brought in.

Size-up considers factors like the material type if identifiable, container status, estimated quantity, potential release modes, wind and weather, nearby people and critical infrastructure, terrain, and the presence of victims. With those data, you can set priorities, establish a defensive or offensive posture as appropriate, and outline an appropriate action plan.

Decontamination, PPE selection, and evacuation are actions that come from the risk-based plan. Decontamination is a response step if exposure has occurred; PPE selection is tailored to the assessed risk level, and evacuation is a protective action implemented based on the hazard assessment. None of these define the basis for the assessment itself—the size-up provides the information that drives the risk-based response.