Which structural feature may cause a fire to become ventilation limited and increase the fuel content of the smoke?

• A. Atriums
• B. Window
• C. High ceiling
• D. Metal roof deck

Answer: (C)

A high ceiling creates a larger room volume, which makes it harder for the fire to get enough air through the openings to sustain complete combustion. When the oxygen supply from ventilation is insufficient for the increased air demand, the fire becomes ventilation-limited. The result is incomplete burning and more fuel-rich smoke, so the smoke contains a higher fuel content. In such spaces, hot gases stratify near the ceiling, further limiting oxygen in the lower layer and promoting the buildup of dense, fuel-laden smoke.