What occurs during Stage 4 pyrolysis beyond free burning?

In the context of fire dynamics, Stage 4 pyrolysis refers to the advanced phase of the pyrolysis process where the decomposition of organic materials reaches a critical point, leading to significant changes in the material's structure and combustibility. During this stage, the heat from the fire causes the degradation of the material and the release of volatile gases, which can ignite, resulting in complete ignition. This is indicative of a fire that has transitioned into a fully developed stage, where the energy output is maximized, and flaming combustion occurs throughout the involved materials.

Complete ignition signifies that enough heat and flammable gases have accumulated to sustain combustion, leading to the rapid release of energy characteristic of this advanced phase of a fire. Understanding this stage is crucial for safety officers, as it informs critical decisions about fire suppression strategies and safety measures to protect personnel and property.