If first-arriving units can only focus on one area, they should prioritize:

Prioritizing the limitation of fire spread to uninvolved properties or areas is crucial in emergency response as it is vital for preserving lives and minimizing damage during an incident. When a fire occurs, the primary mission is to prevent it from spreading beyond the involved structure, which could endanger additional lives and lead to more extensive property damage. Focusing on controlling the fire's edges and ensuring it does not spread allows for a more manageable situation and provides critical time for other tactics to be employed effectively.

This approach underscores the strategic importance of maintaining a boundary for the fire's progression, which safeguards not only the immediate surrounding structures but also facilitates broader community safety. Evacuating persons from the building, while important, may become secondary if the fire spreads beyond control. Protecting nearby structures would be part of overall fire spread limitation efforts, but it requires the initial step of containment. Controlling ventilation is also a valid consideration, but doing so becomes less effective if the fire is allowed to spread, as ventilation can unintentionally increase fire intensity and spread if not properly managed. Thus, limiting fire spread serves as the foundation for all subsequent fire control decisions.