Which type of ventilation operation is used solely as a defensive tactic?

The trench ventilation operation is specifically employed as a defensive tactic during firefighting operations. This technique is particularly effective in controlling fire spread in large, flat structures with a significant amount of fire load. Essentially, trench ventilation involves creating a long, narrow opening in the roof, which allows the heat and smoke to be expelled from the building, while simultaneously preventing the fire from spreading further in that direction.

By using this method, firefighters can reduce the overall heat and smoke accumulation within the structure, thereby protecting adjacent areas and making it safer for either retreating individuals or for other operations. Trench ventilation is about controlling the fire’s path while minimizing the risk to firefighters and bystanders, making it distinct from other types of ventilation that may have more offensive or aggressive objectives.