Certified Fire Investigator Practice Exam

What causes Backdraft to occur during a fire?

1. Excessive humidity in the compartment

2. Overabundance of fuel and heat

3. Depletion of oxygen due to fuel consumption

4. Inadequate water supply for extinguishing

The correct answer is: Depletion of oxygen due to fuel consumption

Backdraft occurs when there is a significant depletion of oxygen in a compartment during a fire. As a fire burns, it consumes the available oxygen in the space. When the oxygen levels drop significantly, the fire can become smoldering or even extinguished. If fresh oxygen is suddenly introduced into the compartment, for instance, by opening a door or breaking a window, it can lead to a rapid combustion event. This sudden influx of oxygen can reactivate the smoldering fire, causing an explosive or violent flare-up, characteristic of a backdraft. The other options do not accurately describe the mechanism behind backdraft. Humidity may affect fire behavior, but it is not a direct cause of backdraft. An overabundance of fuel and heat can contribute to a fire's intensity but does not directly relate to the backdraft phenomenon. Similarly, inadequate water supply is about extinguishing fires, not the dynamics of oxygen levels leading to a backdraft. Therefore, understanding the critical role of oxygen depletion in the backdraft process is key to recognizing and mitigating this dangerous situation during firefighting operations.