What is a backdraft?

A backdraft refers to a combustion phenomenon where a fire in an oxygen-depleted space encounters a sudden influx of oxygen, often through an opening created by a fire fighter or an explosion. When the oxygen is reintroduced to this environment, the previously smoldering or dying fire can reignite explosively, resulting in a rapid and violent combustion known as backdraft.

This occurs because, in an oxygen-deficient environment, combustible material may still be present but is unable to burn efficiently due to the lack of oxygen. When fresh air is introduced, the added oxygen allows combustion to resume explosively, which can be extremely dangerous both for firefighting operations and for anyone within the vicinity of the incident.

The option that identifies a sudden fire flash from increased oxygen describes the critical component of backdraft: the sudden reintroduction of oxygen that leads to a violent reaction. This phenomenon is crucial for fire investigators to understand, as recognizing the signs of potential backdraft can help prevent accidents and injuries during firefighting efforts.