What is a smoke-laden backflow, and how can it be controlled?

• A. Backflow cannot be controlled.
• B. Smoke moving with expected path.
• C. Backflow is a feature of wind-driven fires.
• D. Smoke moving against expected path due to pressure differences; controllable by door/window management and containment.

Answer: (D)

Smoke-laden backflow happens when pressure differences between spaces push smoke to flow opposite the path you’d expect. This movement is driven by openings, stairwells, doors, and other ventilation paths that create higher or lower pressures in different areas, causing smoke to move back into places that should be less affected. It is controllable by door and window management and containment—keep doors closed to maintain compartment boundaries, control which openings are used for ventilation, seal gaps, and confine smoke to a defined area so it can be managed or vented safely.

The other statements miss what backflow actually describes or ignore how it can be controlled: backflow isn’t inherently uncontrollable, smoke can move against the expected path due to pressure, and while wind-driven fires involve pressure effects, the essential point here is the opposite-direction movement and how to limit it through containment and ventilation control.