Which statement is a recognized indicator of potential backdraft?

• A. Dense, dark smoke
• B. A steady flame front
• C. Light smoke with cold air
• D. No signs of heat

Answer: (A)

Dense, dark smoke signals a space filled with hot, fuel-rich gases that aren’t burning due to limited oxygen. When air is suddenly introduced, those gases can ignite violently, producing a backdraft. This makes dense, dark smoke the best warning sign among the options, because it shows the fire is ventilation-limited and accumulating unburned gases that could flash when air arrives. The other signs describe different fire states: a steady flame front means ongoing combustion with sufficient oxygen; light smoke with cold air suggests cooler, less heated conditions; no signs of heat implies little to no active fire.