Ventilation is one of the primary functions that most of us think of when we discuss truck work. Thoughtful and well-timed ventilation is a key factor in life safety, for the occupants and firefighter, as well as providing property conservation — all key strategic goals.
Most fires will naturally ventilate given enough time to degrade the building. However, tactical ventilation involves opening ventilation paths with the intent to make the fire behave or travel in a certain direction.
We are gaining a greater understanding of the impact contents in modern buildings and building construction have on ventilation. There is some outstanding work being done that will help us understand our need for and the impact of tactical ventilation. Some of that work includes studies on wind-driven fires and ventilation by UL.
Life of a fire
Fire will transition from incipient, to growth, to fully developed and to decay stages. At the decay stage, it's usually the lack of oxygen that is keeping the fire suppressed.
An undisciplined firefighter's desire to take the window is often all that is needed to rapidly give the fire enough oxygen to create a fire-induced flashover. The key is knowing what happens after you vent.
When it comes to safety and ventilation the most important thing is coordination with the engine company. Too often the hand line brought to the fire is appropriate for the quantity of visible fire — but not smoke. Once ventilation occurs the amount of fire present is far beyond what the hand line can handle — and God help the engine team if they happen to be inside during this rapid introduction of air.
Being able to read smoke and understand the impact oxygen will have on the event is a key tool for both the outside vent team as well as the engine team. I've seen really experienced engine officer know to stage their team just off the porch steps when horizontal ventilation occurs. This extra few feet back and below the front door allowed them to keep the line in play, rather than being driven out into the front yard.
In general, ventilation should occur as close to the seat of the fire as possible with the intent of drawing out the byproducts of both the fire itself and the fire suppression activities. When choosing the hole(s), we need to think about location of victims, firefighters and the fire.
Building use and type of construction will influence the ventilation profile. Another influencing factor is what stage the fire is in and what will happen when additional oxygen is introduced. Again, the key is where the fire goes after the hole is open not where the fire is now.
It is important to understand that ventilation operations are a human resource black holes. The time and energy needed to properly provide solid horizontal or vertical ventilation will require quite a few personnel; commanders need to realize that properly timed ventilation will require those extra team members.