Smooth vs Fog: The Debate that Really Isn’t
Sooner or later the topic was going to be brought up, so lets’ talk about it.
The history of the Fog nozzle was designed with good intentions, compartmentalized ship fires in a noncombustible room. Lloyd Laymen laid out his research and justification in his manual detailing the science behind the fog nozzle. Where things go bad is when the American fire service salesmen grasp on to this technology and proclaimed its glory all over the United States. Departments were sold that this technology was going to put out fires faster and better than the time-tested smoothbore. Because this was new and more complicated technology, they could increase sales and profits.
Because of this, more research continued, including in my backyard in Iowa with the Royer and Nelson research at Iowa State University, where the Iowa formula was developed. This was great research at the time but was implemented incorrectly and still to this day is misinterpreted. The Iowa formula was tested in compartmentalized structures with a 30-degree fog for 30 seconds. This was the initial knock from the exterior of the building. This created a victim’s last mindset by exposing the victims inside to increased heat and steam without the FD occupying the interior of the structure. In addition, our modern building construction is not compartmentalized and we are not running 30-degree fog because of the air entrainment factors in our oxygen-limited fires.
Disclaimer, Fog nozzles have a purpose and defined tactical use. Fires in voids, attics, or any time we want to use steam conversion to impact the fire tetrahedron, we can use fog nozzle to do so. These situations allow for steam to travel, take the heat and oxygen out of the compartment, and extinguishes the fire. I also believe things like trash fires, car fires, and rubbish fires are better fought with a fog nozzle. When we say fog, it’s a fixed gallonage at low pressure. We will get into the High Pressure some other time.
2.5” should flow minimum of 250 gpm. 1 1/8” at 50 psi flows 265 pgm.
Why the smoothbore?
Since the inception of the hose, the smoothbore has been a staple in the fire service. This nozzle provides many benefits and some disadvantages. The smoothbore is a shutoff with a solid orifice with no moving parts, while some fog nozzles can consist of more than 50 parts. A motto I like to use, “complexity breeds chaos, simplicity always works”. This makes malfunction nearly impossible with smoothbore. As long as the bale is operational, water will exit. This also allows for greater debris removal which can become vitally important depending on your environments like high rise or older city mains, where debris can happen. Smoothbores have greater reach penetration, and higher flows at low pressures.
When looking at the thermal dynamics of fires, as water passes through, the heat degrades water droplets. I am not going to get into droplet size here but there are some awesome articles that do if you want to research those yourself. I view water droplets as an onion. Onions have layers and as has we peel the onion layers we will have a small onion at the end. So as water droplets pass through heat, the layers of the water droplet are being peeled off by the heat. When the water droplet reaches the burning material, we can have successful extinguishment of the fuel-flame interface as Andy Fredericks use to say. Fog nozzles break the water into smaller droplets as it exits the fog nozzle from hitting the baffle and sidewall at the end. So, when the water is introduced into the superheated environment, the water droplet is quickly converted into steam because of the lack of volume in the droplet.
With smoothbores, the only thing creating separation from the solid bore fire stream is the pull of gravity and force behind the stream. This keeps the water droplets together longer allowing the heat to have little effect on the water as it passes through the superheated environment. When the stream begins to break apart, the water droplet sizes are larger with more volume. The heat degradation on the water droplet is reduced. This causes the water to pass through the heat, dropping to the burning material, and extinguishing the fire at it’s origin.
Reach and penetration are significant factors to the benefit of the smoothbore, especially on the 2.5”. When advancing to the seat of the fire, we want to use the reach and penetration to assist in our push and advancement. Fires are burning faster with an incredible HRR. Because of that, we want to use our reach and stream penetration to begin to impact the fire from further away. When we discuss penetration, this not only includes penetration through the thermal layers but also penetration into the building structure. Smoothbores with a solid stream hit harder with more velocity and force than fog nozzles. This allows penetration of building material like drywall and drop ceilings easier to expose voids spaces and attics.
A few arguments I often hear is that a fog nozzle on a wide fog will save you from flashover conditions and we cannot hydraulically ventilate with a fog nozzle. If you think this, you are wrong by a long shot. First, a fog nozzle on a wide pattern will not save you from a flashover. If you have seen the video in the burn container, this is an LP- gas feed fire. That’s not what we are dealing with in real structure fires and this causes a false sense of security and is going to get someone hurt. Second, if you choose a nozzle based on how well it can ventilate, your priorities are wrong. I addition to that, I have also heard people say, “I have never seen a fire a fog nozzle hasn’t put out”. That may be true but I can also use my screwdriver to pound in a nail and gets the job, but doesn’t mean it’s the best tool for the job. Aggressive, craftsmen of the fire service has preferences for tools because they have experiences with many different ones. They choose the tools which sets them up for success, they know how to operate, and provides them with the best chance of winning. They have preferences cause it matters and because they take their job seriously. I prefer my Malvenworks Hawk tool and halligan because it’s the highest quality with the features that best works for me. I have tried three-piece halligans, they suck. so I do not use them.
Nozzles are the most important aspect of fire suppression equipment and not understanding them or purchasing the cheapest bid compromises the firefighter’s ability for fire extinguishment. We have to provide our firefighters with the best tool for the job and I believe smoothbore nozzles especially on 2.25” or 2.5” lines is a must!
I could go on, so maybe we will revisit in part 2.