How does a backdraft occur?

A backdraft occurs when the conditions within a confined space lead to the depletion of oxygen due to combustion. As a fire burns, it consumes available oxygen, creating a low-oxygen environment. Eventually, this can cause the fire to enter a smoldering phase if the oxygen levels drop significantly. When the door or window to that space is opened or a breach is created, it allows air—rich in oxygen—to rush in suddenly. This influx of oxygen can ignite the accumulated flammable gases and smoke that have built up in the confined area, resulting in a violent explosion or rapid combustion.

The reason this scenario clearly defines a backdraft is tied directly to the interaction between the lack of oxygen and the sudden reintroduction of it. It’s this specific combination that can turn a smoldering fire into a highly dangerous event, posing significant risks to anyone present. Understanding this process is crucial in firefighting and safety protocols to prevent backdraft situations.