By David Rhodes
My Introduction to Research
When I first read the Underwriters Laboratories (UL) study on horizontal ventilation, I was a little confused having grown up in the “venting equals cooling” era. With most of my experience with ventilation that occurred during active fire being vertical ventilation, the horizontal study made sense, but I was more interested in “real” ventilation and that would be vertical ventilation. After attending a class that was delivered by one of the lead researchers on horizontal ventilation, I approached this individual with both caution and curiosity. I asked a few questions about the conclusions and then quickly shifted to “What about vertical ventilation?” He told me that the proposal for the vertical ventilation study had been approved. I proudly offered up that it was my experience that I had never lost a structure that we were able to vertically ventilate. This young researcher, Steve “Baby Face” Kerber, nodded and said the he would like me to participate on the panel for the vertical ventilation study. I promptly agreed and immediately began developing my strategy on how I would use my years of experience and knowledge to set these scientists straight!
During my first trip to the Northbrook (IL) UL facility, I met the rest of the vertical ventilation panel, a very diverse group representing departments from all over the country. Small departments, large urban departments, and suburban departments all were there at the table. I felt confident that this was going to go well and that my fellow cohorts would be thinking just like me-vertical ventilation is the one thing that saves the day! A couple of the smaller department guys talked about the fact that they didn’t use vertical ventilation because they didn’t have enough resources to get it done. Then the guy from the Fire Department of New York (FDNY) spoke up: “We don’t get on pitched roofs.” WHAT?!? (I held back the voice in my head.) The FDNY doesn’t use vertical vent on pitched roofs? Then another large urban department said the same. My confidence in the American fire service dwindled. Then the guy from Milwaukee spoke up, “We open up just about every time, and on most of the old structures we end up having to cut the entire roof off for overhaul because of the wood shakes.” REDEEMED, I thought. This went on and on for about three hours. The first lesson I learned was that there are many differences in tactics based on a multitude of factors, and what may work well for you isn’t practical or doesn’t work in other places.
After a few months of planning, we finally started the actual vertical ventilation experiments. This included test burns in both a one- and two-story residential structure. This is important to always keep in mind, and while oxygen and fire interact in the same basic way in every structure, there is a big difference in the operations at a one- and two-story house vs. a 20-story tenement. My personal belief at the time was that if we were going to prove anything it was going to be that we needed to abandon the four-by-four-foot hole and cut much larger ones. What size this would be I didn’t know but I recalled the instructions of my old battalion chief when I was assigned to the truck, “Cut me a hole up there big enough to drive the truck through!” I figured that was where we were headed. Again, my experience with vent holes was very positive and resulted in positive outcomes on the incidents I had been at.
When we conducted the four-by-four-foot vent hole experiments, the results showed that the fires got bigger with the opening of the roof. (Note: We were only testing ventilation; no water was applied prior to opening up.) This was the same conclusions that the horizontal study had shown, and so I began to question how this was possible. I looked for flaws in our experiments. I broke the points off all the little pencils that the scientist used to write things down, and I hid the pencil sharpener. Then it was time for the four-by-eight-foot hole. This would undoubtedly make a difference. The fire was started, the timing was executed, and the four-by-eight-foot hole was opened up and the fire got bigger faster. Doom dark depression, excessive misery, doom, despair, and agony fell on me. Something was NOT right here. This did not match my experience in the field. Maybe it was the lab setting. We were indoors, where there were no wind, trees, or birds. Maybe it was the lack of humidity up here in the north. Maybe this whole thing was rigged to suit one of these guy’s agendas.
Confusion and Delusion
Some of the panel members seemed to understand what went on. Me, not so much. Back at the hotel, the real debates began. This whole research thing was new to me, so I had no context to fall back on. I wasn’t thinking things through and putting them in perspective. I was only thinking about my experiences on the scene of real fires. So, what was the difference? I had to throw it out there. How could I have had such overwhelming success with vertical ventilation but I just saw with my own eyes that things get worse when you open up? Someone much smarter than me chimed in. How long does it take for your crews to get a line on the fire? Are they usually close to the fire when you open up? Yes, they are. In many cases, water is already being applied. Ah ha! But that means that the engine folks have something to do with this vertical vent thing working … no way … that is blasphemous and impossible!
Another person offered up, “You have to consider what’s burning also. If you have a low heat release rate, then you might get a good lift and improve the conditions temporarily. You at least have much longer to get your line in place than you do if it’s something like a sofa or bed burning with a high-heat release rate.”
Huh, what did he say? What’s that got to do with anything? A fire is a fire, right? Wrong! Second lesson learned. I am really dumb, and I better figure out what heat release rate is before I open my mouth again.
Enter Dan Madrzykowski, another scientist who was not working with UL but was camped over at the National Institute of Standards and Technology. He was the guy I needed to do some explaining about heat release rate and ventilation limited. I still didn’t trust these scientist folks, but at least Dan had a mustache and wasn’t a clean-shaven baby face, so I approached him a little more relaxed as the mustache gave him a little bit of fire knowledge credibility. He put several things into perspective.
In the end, I boiled it all down to a few simple lessons learned: There are many differences in tactics based on a multitude of factors, and what may work well for you isn’t practical or doesn’t work in other places. Judging other departments’ tactics without understanding the differences in construction, hazards, and resources needed is a mistake. There is no one magic tactic that works in every situation (except water).
While I considered myself an experienced firefighter and command officer, my knowledge of fire behavior was extremely limited and somewhat out of context. There is more to it than heat, fuel, oxygen, and the chemical chain reaction. Ignorance is not knowing you don’t know, so at this point I at least erased my ignorance and I knew I didn’t know.
What’s burning and how long it has been burning are much more important than I ever realized.
You can’t assume that all fires will behave the same based on your own your past experiences. My fires were primarily vacant structures that were empty. The structure itself was burning, and we put a lot of people on the scene quickly; water application and roof vent happened almost simultaneously. If it didn’t, there was still time for us to react and win the fight. Not realizing this at the time, I would not have thought twice about opening that roof up prior to having a hose in place in an occupied, fully furnished house or apartment with a different fuel load. In doing so, I could have made things worse.
Vent limited is very similar to being too rich to burn. It’s no different than a gas leak. Fire behavior is fire behavior, but what’s burning (a sofa or a wood wall) and the size of the space determine how fast the oxygen is used up and how fast the fire will react to the introduction of more oxygen.
I Wasn’t All Wrong: A New Perspective
When this project was complete, I emerged still a proponent of vertical ventilation on low- to moderate-pitched roofs when adequate resources are available, members are adequately trained, and the operation is coordinated with an interior attack. There are many out there who say the research and researchers say not to ventilate, and they would be WRONG. I have never heard anyone involved in research say or believe that. What I have heard is an explanation of what happens when you ventilate and how important it is to coordinate it with water application.
If the truck gets to the roof before the line can get to the fire, remember: You can make the cuts and hold on opening until the line is in place. The perfect time to open the roof is just before the line opens up. Heat rises, and that’s a really efficient way to let it out. If resources are not available, then the resources should be committed to getting the water to the fire and then using a horizontal or positive pressure vent. If it’s my decision to make, then it’s always based on the resources available, not what another department does with different resources.
David Rhodes is a 32-year fire service veteran. He is a chief elder for the Georgia Smoke Diver Program, a member of the Fire Department Instructors Conference (FDIC) International Executive Advisory Board, a hands-on training coordinator for FDIC, an editorial advisor for Fire Engineering and the UL Firefighter Safety Research Institute, and an adjunct instructor for the Georgia Fire Academy. He is a Type III incident commander for the Georgia Emergency Management-Metro Atlanta All Hazards Incident Management Team and is a task force leader for the Georgia Search and Rescue Team. He is president of Rhodes Consultants, Inc., which provides public safety training, consulting, and promotional assessment centers.
