In revising the classic four stages of fire development, the phase that has been expanded upon is:

The growth phase of fire development has received significant attention and expansion because it is during this stage that the fire transitions from a small, contained ignition to a more vigorous and dangerous state. Understanding this phase is crucial for firefighters and safety officers, as it highlights how quickly fires can escalate and the behaviors of fire in this stage.

In the growth phase, various factors come into play, such as fuel availability, ventilation, and the fire's temperature. This phase can lead to flashover, a critical moment when the fire grows rapidly and becomes uncontrollable. By studying the nuances of the growth phase, professionals can develop better strategies for fire containment and suppression, recognizing the signs of escalation and responding appropriately.

This comprehensive understanding allows for improved training and preparedness, ultimately enhancing safety measures both for responders and the public. The focus on the growth phase helps emphasize the importance of early detection and intervention in fire scenarios.