The size-up process of an emergency incident begins:

• A. After first-arriving resources arrive and continues throughout
• B. Before an incident is reported and continues throughout
• C. Before interagency aid arrives and after reciprocal payment is taken
• D. After the incident is terminated through the post-incident analysis process

Answer: (B)

Size-up is an ongoing assessment of conditions, risks, and actions that starts as soon as there is any indication of trouble and continues through the entire incident. You begin forming an initial hazard and resource picture before a formal incident is reported—even during dispatch or pre-arrival cues—so you can prepare and position resources appropriately. As responders arrive and more information becomes available, you update your assessment and adjust tactics, safety measures, and resource needs. This continuous process extends from the earliest moments through response, action, and into post-incident analysis to capture lessons learned.

Starting size-up only after first-arriving units arrive delays crucial risk awareness and decision-making. And focusing it only before interagency aid arrives or only after termination ignores the needed ongoing evaluation throughout the incident.