Backdraft is ignition of accumulated gases when air is introduced; flashover is simultaneous ignition of contents in a room; two prevention strategies include

• A. Ventilation-only to remove gases.
• B. Early detection and applying water to cool.
• C. Sealing all openings to stop air exchange.
• D. Ignoring warnings.

Answer: (B)

Backdraft and flashover are both extreme fire behaviors that can trap occupants and responders. The best way to prevent them is to catch warning signs early and to reduce heat in the environment. Early detection provides the warning signs that a dangerous condition is developing—rapid heat buildup, increasing smoke, changes in smoke color or velocity, or vents puffing—and lets you take action before ignition occurs. Cooling with water directly lowers the temperature of the fuels, contents, and surroundings, which slows or stops the chemical reactions driving the fire and reduces the likelihood that accumulated gases will ignite when air is introduced or that the room reaches the temperature for flashover.

Ventilating a space to “remove gases” can actually bring in the air that triggers a backdraft, and sealing all openings traps heat and gases, potentially making things worse. Ignoring warnings is unsafe. So combining early detection with cooling is the most effective match for preventing these dangerous conditions.