Which term describes an explosion resulting from the sudden introduction of air into a confined space containing oxygen-deficient products of incomplete combustion?

• A. BLEVE
• B. Backdraft
• C. Conduction
• D. Rollover

Answer: (B)

Backdraft occurs when a fire burns in a confined space with limited ventilation, so the room fills with hot, fuel-rich combustion gases and very little oxygen. If air is suddenly introduced—by opening a door or vent—the fresh oxygen mixes with those hot gases, and the accumulated fuel ignites explosively, causing a rapid pressure surge. This explosive ignition is the result of the sudden reintroduction of oxygen to partially burned products, not a steady flame front. BLEVE would involve a pressurized vessel rupturing due to heat, conduction is simply heat transfer through materials, and rollover describes flames moving across a surface of a flame layer, not an explosion caused by air entering a confined space.