What essential function occurs first upon arriving at a fire scene?

Upon arriving at a fire scene, the essential function that occurs first is known as size up. This process involves a thorough assessment of the scene to gather vital information regarding the fire's nature, its location, the surrounding environment, and any potential hazards. Firefighters look for things such as the building's construction type, the presence of occupants, visible smoke or flames, and other critical factors that will influence response tactics.

Conducting a proper size up helps establish initial operational priorities, including whether to proceed with offensive or defensive strategies, the need for search and rescue operations, water supply considerations, and evacuation protocols. Essentially, the size up allows incident commanders and teams to make informed decisions and prioritize actions that will ensure the safety of both victims and firefighting personnel. It is the foundational step that directs all subsequent actions and strategies on the fire scene.