Certified Fire Investigator Practice Exam

Which of the following events can prompt a Backdraft?

1. Cool air influx into a fire environment

2. The removal of oxygen from a confined space

3. An open flame contacting volatile substances

4. Immediate extinguishment of flames

The correct answer is: Cool air influx into a fire environment

A backdraft can be triggered when cool air is introduced into a fire environment, typically through an opening created by ventilation efforts or structural failures. This influx of cool air may lead to a sudden re-ignition of combustion when it mingles with the heat and unburnt gases present in a superheated environment. The mixture can reach a point where it becomes combustible, especially in an area that was previously oxygen-deficient due to burning processes consuming available oxygen. This phenomenon occurs because as a fire consumes oxygen, it creates a vacuum that draws in external air. If enough oxygen-rich air enters into the hot, smoky, and potentially explosive environment, it can cause the accumulated flammable gases to ignite violently, resulting in a backdraft. Understanding this dynamic is critical for fire investigators and responders to anticipate potential hazards when approaching a fire scene. While the other options may involve fire dynamics and chemical processes, they do not directly lead to the specific event of a backdraft. For instance, removing oxygen from a confined space would not prompt the ignition of gases but instead extinguish a fire. An open flame contacting volatile substances typically results in flames spreading rather than the backdraft phenomenon, and the immediate extinguishment of flames would halt combustion, rather than create conditions for