Which type of ventilation is used to stop the horizontal spread of fire in a long, narrow building?

Trench ventilation is specifically designed to control the spread of fire across the horizontal plane in long, narrow structures. This technique involves creating a trench cut in the roof, which allows hot gases and smoke to be vented out while preventing the fire from extending laterally. By cutting a long, narrow opening at a distance from the fire, firefighters can reduce heat buildup, making it possible to combat the fire more effectively from a position of safety.

In contrast, roof ventilation primarily focuses on removing hot gases and smoke from the overall structure but may not specifically target the lateral spread in elongated spaces. Vertical ventilation is mainly aimed at releasing heat and smoke vertically from a building's upper levels, which may not be sufficient in preventing horizontal fire spread. Cross ventilation typically refers to introducing air flow across the building, which can help with smoke movement but doesn't inhibit the horizontal spread of flames. Thus, trench ventilation is the most effective strategy in these scenarios, efficiently addressing the unique challenges posed by long, narrow buildings.