What is introduced when a window breaks or a door is opened during a fire?

When a window breaks or a door is opened during a fire, additional oxygen is introduced into the environment. Fires require three elements to sustain combustion: heat, fuel, and oxygen, which is often referred to as the fire triangle.

When a breach occurs, such as a broken window or an opened door, it allows the surrounding air—rich in oxygen—to enter the fire zone. This influx of oxygen can lead to a significant and rapid increase in the fire's intensity. As the fire receives more oxygen, it can spread more quickly and the flames can grow larger, leading to a phenomenon known as "flashover," where everything in the room ignites almost simultaneously due to the increased temperature and available oxygen.

This principle is critical for fire investigation and firefighting strategies, as controlling the environment and managing oxygen levels can be pivotal in either mitigating a fire or understanding how it progressed. Therefore, recognizing the impact of introducing additional oxygen through openings during a fire is essential for fire professionals.