By Sean Gray
The tale of “Pushing Fire” has long been told from firehouse to firehouse for many years. Should we discount these claims even though research has proved that it’s not possible to push fire? The simple answer is NO; however, we should ask more questions in regard to the experience of those who say they have seen it or possibly even had an experience where they were “steamed.” Ask questions about these incidents.
Was there a fire ball that caused the fire to spread farther, or was it a movement of gases that created the mixing of fuel, heat, and oxygen that appeared to be the pushing of fire? Was the stream being used as a fog pattern? Where was the stream placed? Did the stream cover the circumference of a window that was an outlet for venting fire? Was the straight stream whipped to cover the opening? These are all questions that should be asked when hearing a war story about the evil of exterior streams or transitional attack.
It appears that a straight or a solid stream has become the stream of choice among American firefighters because of what we’ve learned from firefighter safety research. We cannot push fire with water! What does that mean exactly? Fire gases can be moved and pushed by air from a hose stream, known as “air entrainment.” It’s important to note that fog streams have more CFM’s of air behind them when compared to a straight stream. However, straight streams can still move a significant amount of air depending on the extent of nozzle movement. Fog and straight streams can push steam and gases. When used incorrectly during exterior attack through a window, the stream can overcome the exhaust outlet of the fire and change the flow path. Photos 1-3 illustrate what NOT to do.
(1) WRONG! The fog stream covers the window, preventing the fire from venting. This could cause a push in steam and gases to the interior of the structure. (Photos by author.)
(2) WRONG! The firefighter is whipping the stream in a circular motion and creating a broken stream similar to the fog stream in photo 1. The result will be the same, but there will be a slightly less amount of air from the nozzle.
(3) WRONG! The firefighter is standing too far away. The stream is breaking apart and hitting the center of the room, causing the water to travel to the rear wall. Half of the room is being missed because the stream is not hitting the ceiling near the window.
(4) RIGHT! In a transitional attack, it is critical to place the stream inside the window. The stream should be narrow and enter the window without any movement, allowing gases to exit past the stream on the sides of the window. The water will surf across the ceiling, cooling surfaces.
Firefighters typically are not taught exactly where to place the hose stream. As technology in nozzles continues to advance, the focus seems to be on the amount of water being delivered, combined with the lowest nozzle tip pressure instead of how the water is being delivered. We’re not saying that flow rate and tip pounds per square inch aren’t important. It’s essential to have the proper nozzle flow and pressure matched with your hose type and size. We’re not here to argue smooth bore vs. fog nozzles. The focus today is on what we do with our straight/solid hose streams.
RELATED
Training Minutes: Air Entrainment and Hose Streams
UL FSRI Releases Part II of the Fire Attack Study: Air Entrainment
Burning Down the House: A Practical Way to Demonstrate Fire Behavior
In the recruit academy, we are taught the T-Z-O hose stream placement. Is this really all that effective? Why is it that our counterpart police officers spend countless hours focusing on hitting their intended targets and we teach our recruits the T-Z-O pattern because it’s in a textbook. Some fire service experts believe that the best option for killing a fire is to flow as much water as possible as you move through a structure. I agree that it is essential to flow enough water to protect yourself and fellow firefighters, but let’s take it a step further by striving to be masters of our craft and including hose stream target practice. We need to understand that our hose streams can affect flow paths and push products of combustion into places we don’t want them to be.
Air Entrainment
Movement of the nozzle is critical because of the air entrainment that can be created by rapidly moving or whipping the nozzle around. Studies have shown that even a smooth bore nozzle when moved rapidly in a circular fashion can create approximately 6,000 cubic feet per minute (CFM) of air movement. Air currents can push steam or gases onto potential victims. Understanding how much air a particular hose stream entrains will help us understand how to better use the hose stream for its intended purpose.
By applying the research with fireground experience and training, we have found that using a rainbow nozzle movement for interior fire attack works best. Flow water into rainbow shape toward the top of the wall, across the ceiling, and toward the opposite side at the top of the wall. It’s best to flow water at each turn, or continuously, if needed while inside the structure. Some describe this as the “wall- ceiling-wall technique,” “N pattern,” or “inverted U”. Regardless of the name, the purpose of this technique is to cool the upper surfaces; minimize air entrainment; and decrease the disruption of the neutral plane, which leads us into what the water droplets are doing once they strike the surface.
We, like most firefighters who came up in the early 1990s, have seen fire “pushed”; but just because we saw it with our own eyes, doesn’t mean that we understood what we were seeing. Go back to Firefighter Essentials, 2nd edition, and you’ll see figures of 30° fog patterns in hallways. That’s what we were taught back then. Hence, the reason we think that we’ve seen fire “pushed.” We didn’t realize that the water wasn’t actually pushing anything, but that the air behind the stream was pushing combustible gases. Water cannot move its away around corners and into hallways. Gravity makes the droplets fall into the initial room, and velocity takes them straight until they fall from gravity. However, air pressurizing a space will move around corners. Water droplets falling onto flame extinguishes fire. Air moves combustible gases. Know your nozzle patterns and the CFM being produced by your nozzle. It’s important to understand what happens when the water leaves the nozzle, not just how to deploy and move hose though a structure.
One thing that cannot be denied is that water application into a fire room makes everything better. Even if it’s applied incorrectly, temperatures will still decrease when water is applied. Transitional attack arguably requires more nozzle technique than interior attack. Embrace the application of exterior streams on your fireground, and educate yourself and your crew on the correct application for a transitional attack. It’s not something you will need on every fire, but you should use it when it is indicated. Focus the argument on what is the fastest way to get water onto the fire, no whether the attack should be interior or exterior. Remember, fast water on tank water and get it done!
BIO
SEAN GRAY is a captain with Cobb County (GA) Fire and Emergency Services and has been in the fire service since 1993. He has been a member of multiple technical panels involving firefighter safety research and is an appointed member of the UL-FSRI Advisory Board. He recently co-authored a PennWell DVD and book The Evolving FireGround-Evidence-Based Tactics.
