A violent fire of explosive force resulting from the introduction of oxygen to a smoldering fire with high heat and high fuel vapor concentration is called?

• A. Backdraft
• B. Flashover
• C. Puffback
• D. Rollover

Answer: (A)

Backdraft is a violent explosion that happens when oxygen is introduced into a space where a fire has been smoldering at high heat with a high concentration of unburned fuel vapors. The fire has consumed much of the room’s oxygen and produced a dense layer of flammable gases; when air suddenly enters, those gases mix with the oxygen and ignite explosively. This scenario—high heat, fuel-rich vapors, and a sudden oxygen supply—is what drives the explosive force. It differs from flashover, which is the rapid ignition of all fuels in a space caused by heat buildup rather than a fresh oxygen influx, and from puffback or rollover, which involve different fire behaviors not centered on an oxygen-driven explosion from accumulated gases.