video credit: Smooth Bore Cartel

Fire doesn't go out for three main reasons: either there's insufficient water being applied, the water isn't being applied correctly, or it is fueled by an accelerant (e.g. gas line leak). This article will closely examine the work of the Fire Service Research Institute (FSRI) to help us determine the best methods for applying water during an interior fire attack. Although air entrainment is also a crucial consideration for a successful fire attack, it won't be covered in the scope of this article. With that said, the water application discussed in this article should be performed using a solid or straight stream.

How water is distributed in a compartment is commonly known as water mapping. When water hits a surface, it doesn't bounce back like a tennis ball would behave. Instead, it breaks up and the momentum pushes the water in all directions along that surface. Water’s high surface tension helps allow it to run the surface (e.g. a ceiling) until it either hits another surface (e.g. a wall) and is translated along that new surface or it loses momentum and is overcome by gravity. To illustrate this on the training ground, have someone stand in the middle of a room, and have the nozzle firefighter flow water at the ceiling of the room. The person standing in the middle of the room will not get wet, instead the water will run along the ceiling and then down the walls. It’s important to note, the path of the water is dependent on its angle of impact; during the demonstration, experiment with different stream angles and observe how the water behaves. Now let’s apply this concept to the residential fire attack. 

Think of a single-family dwelling as a large box filled with smaller boxes. Utilizing surface cooling concepts, the nozzle team should combat the fire by controlling one box at a time. Since heat and smoke take the shape of the box, the fire stream must also take the shape of the box. Simply put, we aim to cool all surfaces with water. Surface cooling is essential for successful extinguishment because it stops the heat absorption and subsequent reradiation from hot surfaces, which contribute to the heating of fuels, resulting in accelerating fire growth. As a result of surface cooling, gasses in the compartment will also cool and therefore contract. When gasses contract, it creates “lift,” allowing fresh air to enter the compartment from behind the nozzle team and thus improving oxygen levels.

To illustrate the concept of surface cooling, let’s examine a push down a hallway that has fire impingement from the room of origin. In the hallway, the nozzle firefighter applies water using the “Wall-Ceiling-Wall” technique. This will place minimal water in the fire compartment but it will cool the surfaces in front of the nozzle team. Before making the advance, the nozzle firefighter should “sweep” the floor with the stream to cool it, and if present, it will clear loose debris ahead of them. Up to this point the article has discussed the importance of flowing water at a steep angle at the ceiling. I want to take a moment to stress that water on the floor also possesses immense value. Although left out of the official FSRI report because it did not meet the parameters of the specific test they were attempting to study, panel members have reported that between burns all carpet was removed and new carpet reapplied. This was done because “it was quickly realized that damp to wet carpet significantly increased the thermal ballast of a residential compartment to a point where fire behavior was impacted severely,” Dennis LeGear, FSRI panelist (ret. Capt. Oakland FD). To put it plainly, water on the ground reduces flashover potential.

Once the hallway is adequately cooled, the nozzle firefighter must decide, based on conditions, training, and experience, whether to continue the fire attack with a flow-and-move or hit-and-move approach. If using a flow-and-move approach, the fire room can be “sealed” by directing the stream at the door jamb and deflecting as much water into the fire room as possible. As the nozzle firefighter advances to the fire compartment, they should begin directing their stream away from the door jamb and into the compartment as their angle permits. If possible, positioning yourself against the wall opposite the doorway on the approach will create the best angle for the fire stream.

Regardless of the approach technique, it’s important to pause at the doorway of the fire room and water map the compartment by flowing water at a steep angle from the hallway. The effects of the fire stream should be noticeable within seconds. However, common reasons for not seeing these effects include a shielded fire (water not able to reach the seat of the fire), water hitting the head or walls around the doorway and not actually entering the room (listen to feedback from the sound of the stream), kinks causing inadequate gallons per minute (GPM), nozzle clogs in combination nozzles, or the bail not being fully open. Once inside the compartment, the nozzle firefighter should cool all burning surfaces by directly applying water to them. 

This article only scratches the surface of the science behind proper water application, and I understand that the science may not resonate with everyone. For those who prefer a simple explanation, I'll illustrate the concept of water mapping like this. Penciling cools gasses momentarily when the bail is open, but since the bail closes immediately, the heat returns immediately. Instead of penciling the fire, erase it by cooling all surfaces. Proper water application, applied early and consistently while moving towards the seat of the fire, reduces overall temperatures, increases the chances of victim survival, and reduces the risk of rapid fire development.

This month, firefighters should practice the principles described in this article by applying water while advancing to the seat of the fire using either the flow-and-move or hit-and-move technique. Ideally this drill is performed in a training facility or acquired structure. If your department does not have a facility readily available, get creative and use pallets and plywood to create a prop (like the one pictured) in order to drill on this fundamental engine company skill.