Final answer:
The first priority when assessing scene safety is your personal safety.
Step-by-step explanation:
In the context of assessing scene safety, the first priority is your personal safety. Before treating the patient, ensuring bystander safety, or considering hazards to the public, it is essential to prioritize your own safety as a rescuer. This includes dressing appropriately with fire-resistant clothing and breathing apparatus if necessary, as well as assessing the fire and situation to report conditions to superiors.