What happens to oxygen-rich air during the free-burning phase?

During the free-burning phase of a fire, oxygen-rich air is drawn into the combustion zone to sustain the fire. This process depletes the available oxygen as it reacts with the fuel in the presence of heat to produce combustion gases. As the fire consumes oxygen, particularly in an open environment, there's a higher demand for oxygen to maintain the intensity of the flames and ensure efficient burning.

The free-burning phase is characterized by rapid ignition and flaming combustion, where the fuel is actively burning and the fire is self-sustaining as long as it has an adequate supply of oxygen. This consumption is what leads to a decrease in the oxygen concentration in the surrounding environment. While the fire is thriving on this supply, the surrounding areas can become oxygen-poor, leading to a decrease in air quality and potential hazards for firefighters and individuals nearby.

Understanding this dynamic is crucial for fire suppression tactics as it highlights the importance of managing air supply during an incident.