In which stage of a fire does the fuel produce heat but has not yet spread to other materials?

The incipient stage of a fire is characterized by the initial phase when the fuel is heated and begins to release volatile gases, but the fire has yet to spread to surrounding materials. During this stage, the process of ignition is underway, and the temperature begins to rise as the fuel starts to undergo pyrolysis. However, the flames have not yet emerged, and the fire is still contained to its starting material.

Understanding this stage is crucial for fire inspectors, as it presents an opportunity for intervention. Recognizing the signs of an incipient fire allows for timely action to extinguish or control the fire before it enters the growth stage, where it can begin to spread more widely and become more difficult to manage. This helps emphasize the importance of early detection and rapid response to potential fire hazards.