Transitional Fire Attack: What the UL/FSRI Research Actually Says

Hit it hard from the yard was never the point. And real firefighters go interior is not a tactical argument. It is an ego argument.

The transitional fire attack, supported by over a decade of research from UL's Fire Safety Research Institute, is one of the most significant tactical evolutions in modern firefighting. And it is still being misunderstood, misrepresented, and resisted by firefighters who have not read the actual research.

What Transitional Attack Actually Is

Transitional attack is a two-phase tactical approach. Phase 1 is exterior application. Flow water from the exterior into the fire compartment through a window or opening. The goal is to cool the fire environment, drop temperatures, reduce the thermal threat, and slow fire progression. Phase 2 is interior attack. After the initial knockdown, transition to an interior attack for final extinguishment, overhaul, and search.

You are not fighting fire from outside. You are resetting the interior conditions to make your interior attack safer and more effective.

What the Research Says

Exterior water does not push fire onto victims. This was the biggest fear, and the research conclusively debunked it. In multiple experiments with instrumented rooms and thermal sensors at victim locations, exterior water application either had no effect on victim exposure or reduced thermal exposure at victim locations. Water applied to the fire compartment absorbs heat and generates steam. The steam displaces hot fire gases. Temperatures drop.

Modern fires reach flashover in under 4 minutes. FSRI comparison studies showed that a modern furnished living room reaches flashover in approximately 3 minutes and 40 seconds. A legacy-furnished room took over 29 minutes. Why? Modern furnishings are primarily synthetic with dramatically higher heat release rates.

Flow path management is critical. The flow path is the most dangerous location in a fire building. When you open a door, you create a bidirectional flow path where fresh air enters at the bottom and hot gases exit at the top. In a ventilation-limited fire, this incoming air can cause rapid fire progression along the flow path. Transitional attack addresses this by cooling the fire compartment before opening the door for entry.

A brief exterior application dramatically improves interior conditions. FSRI experiments showed that as little as 10 to 15 seconds of water applied from the exterior into the fire compartment reduced temperatures by hundreds of degrees throughout the structure.

When to Use Transitional Attack

Use transitional attack when fire is visible from the exterior, interior conditions appear to be at or near flashover, you have a window or opening into the fire compartment, and you are going to make entry anyway.

Go direct interior when fire is small and interior conditions are tenable, fire location is not accessible from the exterior, or you have a confirmed life hazard requiring immediate entry.

The Technique

Set up at a 45-degree angle to the window if possible. Straight stream or solid bore. Put water on the ceiling of the fire compartment. You are not trying to extinguish the fire from outside. You are trying to cool the hot gas layer. 15 to 30 seconds is typically enough. Then stop flowing, move to the entry point, and begin your interior attack.

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