By P.J. Norwood
It has been said that the enemy is our buildings. Each and every generation of firefighters faces this problem with no real solution.
We all have heard phrases such as “the fireground is changing,” “the modern fire environment has changed fire behavior,” and other sound bites from articles, training materials, and instructors across the country. Rightfully, there has been some push-back by some and complete buy-in from others. There is no right or wrong, and both sides have their reasons and discussion points to try to persuade the “other side” from seeing it their way.
I am a believer in the “new” tactics based on my research of the current studies. However, I do feel there are some things we need to validate on the streets. I also feel that the push-back by some is positive; we cannot validate any tactic or discussion point through studies only. Without the studies and research being conducted by the Underwriters Laboratories Firefighter Safety Research Institute (UL-FSRI), the National Institute Standards and Technologies (NIST), and many other groups, agencies and organizations we would not even be having this discussion. Without the vision and mission of the UL-FSRI, we would not have data to study, analyze, and apply to our fireground. Regardless of my belief in the research, I clearly understand it is going to take the fire service a while for everyone to buy in to the tools provided to our toolbox, called “tactical considerations.”
Every fire to which we respond may not fit the ventilation limited model. However, I wanted to share a personal incident that clearly fits this fire model. The incident took place in a residential structure that was being built to exceed efficiency standards. This building was our enemy because of its modern construction practices that made the home almost completely air tight.
My department was dispatched to a reported working house fire. The first-due engine arrived and made the following radio transmission: “Engine 4 arrived, we have nothing showing.” They then requested additional information from the caller. The driver parked the engine directly in front of the house to which they were sent and he and the rider exited. The house was a two-story wood frame residential home elevated approximately 12 feet because of Federal Emergency Management Agency (FEMA) regulations for a home in this flood-prone area. The house was under construction and had limited access. The driver and rider met with the caller, who pointed to the house and said, “That house is on fire.” On further investigation they saw a few wisps of smoke coming out from around a window and visualized multiple other windows soot stained and cracked.
(1)The Alpha side of the two-story elevated home. Note the limited access and lack of visible fire or smoke damage. (Photos by author.)
The members made appropriate communications and commenced forced entry and fire attack. When the ground-level door was forced, they were faced with dark, black smoke under pressure to the floor. (The door forced was the ground level of the elevated home, which is a stairway only; not occupied space.)
The first line was stretched to the first floor, where they faced high heat and zero visibility, described as being similar to a basement fire. The crew had no visible or audible signs of fire, so they continued their stretch to the second floor. The heat continued to rise and visibility decrease. A second line was brought in through the exterior front porch on the first floor and stretched toward the Charlie side (3 side).
At this point, horizontal ventilation had commenced at the entry door when it was forced open, and through the second first-floor entry door for the second line. A crewmember also took a window in the stairway on his way to the second floor. When the first line reached the second floor, the crew found no visible fire and that heat was continuing to rise. The crew decided to begin flowing water above them to cool the environment. At approximately the same time, the members on the first floor experienced an increase in heat and some smoke lift, which allowed them to see smoldering debris and a small area of fire at the floor level. They began flowing water in that area while additional horizontal ventilation took place.
The remainder of the incident went smooth and was uneventful. However, we were very surprised at the amount of fire damage that the home received, especially when there was very little visualization of fire and “nothing showing” on arrival.
(2, 3) These photos show the charring and fire damage to the interior of the home. This was significant damage considering there was very little visualization from interior crews of fire.
During the investigation, I spent a lot of time with the homeowner/general contractor and received an education in modern residential building construction. Many of the things I learned about I had never heard of, let alone fought a fire within. During these conversations, the homeowner quickly realized a benefit to educating me and allowing our department to use his home for training prior to demolition.
In a short time, it was very evident we experienced a ventilation-limited fire in a modern home. The home had a 70+ R-value of the exterior walls and a 54+ R-value of the roof assembly. There were finished trusses on the first floor, all radiant heating including loops in the north walls, a cold roof, and wall construction that also put an air gap between the exterior sheathing and interior of the wall. There was spray foam and foam board insulation throughout as well as an air exchange system, which was the only means of providing an exchange of fresh air with the outside environment. The construction of this home was like nothing we have experienced in the past.
(4) A cross section of the exterior wall during demolition. Note the air gap behind the exterior sheathing and between the blue in color vapor barrier. This concealed space can allow for fire travel from the ground floor up and into the roof components unnoticed.
We established a positive relationship with the homeowner, who let us use the home for training. We were able to take a close look at the construction and bring every member of the department through the home and complete a postincident review. During this review, we were able to discuss modern building construction and ventilation limited fires. This experience proved extremely valuable and taught us many lessons that will be brought to every fire from this point forward. We were also allowed to cut a few holes in the roof. This also proved extremely valuable; we never had the opportunity to cut holes in a residential roof that was 18 inches thick.
(5) The roof while we used standard vertical ventilation tactics to ventilate. Holes were kept small at the homeowner’s request. Tactics had to be altered to accomplish opening this roof. (6) A cross section of the roof that sat on top of two- × 12-inch wood members and which were also filled with standard paper-backed insulation. Notice the air gap, hence the term “cold roof.” This gap connected with the air gap in the exterior walls.
The Impact of Ventilation Study from UL-FSRI lists 12 tactical considerations. For this incident, we saw five items from the study that were pertinent. The tactical considerations addressed within the study that where applicable at this incident follow:
- Stages of fire development. The stages of fire development change when a fire becomes ventilation limited. It is common with today’s fire environment to have a decay period prior to flashover, which emphasizes the importance of ventilation.
- Forcing the front door is ventilation. Forcing entry has to be thought of as ventilation as well. Although forcing entry is necessary to fight the fire, it must also trigger the thought that air is being fed to the fire, and the clock is ticking before either the fire gets extinguished or it grows until an untenable condition exists, jeopardizing the safety of everyone in the structure.
- No smoke showing. A common event during the experiments was that once the fire became ventilation limited, the smoke being forced out of the gaps of the houses greatly diminished or stopped all together. No smoke showing during size-up should increase awareness of the potential conditions inside.
- Coordination. If you add air to the fire and don’t apply water in the appropriate time frame, the fire gets larger, and safety decreases. Examining the times to untenability gives the best-case scenario of how coordinated the attack needs to be. The average time for every experiment, from the time of ventilation to the time of the onset of firefighter untenability conditions, yields 100 seconds for a one-story house and 200 seconds for the two-story house. In many of the experiments, the onset of firefighter untenability to flashover was less than 10 seconds. Treat these times as being very conservative. If a vent location already exists because the homeowner left a window or door open, then the fire is going to respond faster to additional ventilation opening because the temperatures in the house are going to be higher. Coordination of fire attack crew is essential for a positive outcome in today’s fire environment.
- Flow paths. Every new ventilation opening provides a new flow path to the fire and vice versa. This could create very dangerous conditions when there is ventilation limited fire.
During the UL testing, the homes were constructed to standard construction practices; not of these energy conversation standards. Also, UL testing in the lab as well as for many other live burns in acquired structures showed the same ventilation limited fire model. Although you will see this model in homes constructed in this manner, you can also see this in homes of standard modern construction. As a firefighter, company officer, or chief officer, it is imperative you consider this during every building size-up.
In my town, many homes were significantly damaged from Hurricanes Irene and Sandy. Therefore, a lot of new construction has taken and continues to take place, with much more to come within our community in the next few years. The incidence of homes built to these standards will inevitably increase. Each and every fire to which we respond will not fit the ventilation limited fire behavior model. Firefighters, company officers, and chief officers must study the data learn the appropriate tactics and apply when appropriate.
Take the time today to read, study, and learn as much as you can about today’s modern building construction, the impact of ventilation on residential structures, and many of the other topics available through UL-FSRI. Be prepared to change, alter, or adapt your tactics when necessary.
This home and scenario represented an incident with which we were not familiar. We were unaware that the level of construction going into this home would directly affect our tactics. These incident-highlighted residential buildings are the enemy. This scenario also showed us that we must do a better job of getting in and out of all residential buildings during construction. Without the knowledge of what is occurring in our districts, we will increase the chances of making poor tactical decisions and not tapping into the tactical considerations in our toolbox being supplied by the research that has and continues to have a positive impact on the fire service.
P.J. NORWOOD is a deputy chief training officer for the East Haven (CT) Fire Department and has served four years with the Connecticut Army National Guard. He has authored Dispatch, Handling the Mayday (Fire Engineering, 2012); coauthored “Tactical Perspectives of Ventilation” and “Mayday” DVDs (2011, 2012); and was a key contributor to the “Tactical Perspectives” DVD series. He is a Fire Engineering University faculty member, co-creator of Fire Engineering’s weekly video blog “The Job,” and host of a Fire Engineering Blog Talk Radio show. He is certified to the instructor II, officer III, and paramedic levels.