In horizontal ventilation, to avoid venting heat and smoke, where should the vent be placed relative to the window?

• A. On the windward side and slightly above the window
• B. On the leeward side and at the window sill
• C. Directly in line with the window
• D. On the roof edge away from the window

Answer: (A)

In horizontal ventilation, the goal is to create a controlled flow that uses both wind and the buoyancy of hot gases to remove heat and smoke from the building. Placing the vent on the windward side and slightly above the window achieves this best: the wind helps push the smoke toward the opening, while the higher position taps into the rising hot gases, pulling them out rather than letting them spill back inside. This arrangement reduces the chance of smoke or heat re-entering through other openings and makes the environment safer for occupants and firefighters. Venting on the leeward side tends to push smoke back into the structure, venting directly in line with the window can create undesirable backflow, and a vent placed far away on the roof edge doesn’t give as effective a direct path for the hot gases to escape.