Modern Fire Dynamics and Legacy Construction: Lessons Learned

The world-class research that Underwriters Laboratories (UL), the National Institute for Standards and Technology, and the International Society of Fire Service Instructors have done on house fires has greatly advanced our understanding of modern fire dynamics. House fires are our most important alarm, and this work has modernized our tactics to meet the challenges of today’s house fire battlefield. But, what happens when the burning home is legacy construction with modern furnishings?

(1) On arrival, heavy fire was showing at the bay windows. The sole occupant was across the street. (Photo by author.)

This article shares lessons learned from a recent house fire to which the West Haverstraw (NY) Fire Department responded. It links our fireground experience to research results from the UL fire attack study and also provides and reinforces valuable lessons in modern house fire suppression.


This fire was attacked first from the exterior with a garden hose and was effectively suppressed. The hose was then taken to the interior for final extinguishment.

At the time of the fire attack, it was known that no occupants were in the house. A case can be made that this fire attack was an unwarranted risk under the circumstances. The real value of this after-action review (AAR) is an increase in our understanding of applying research-based tactics in a modern residential fire environment. This article does not support attacking a residential fire with a garden hose and without adequate personnel, reserve staffing, and proper fire equipment. It illustrates how several fire conditions lined up to enable firefighters to make a lucky stop. This unorthodox experience is presented only as an example of how important it is for firefighters to understand fire dynamics and to apply the correct mix of water and ventilation in their strategic and tactical decision making and development of modern fire attack procedures.

The Fire

From a fire department perspective, this was a routine and minor fire. It was contained to one room, there were no injuries to civilians or firefighters, and staffing and water supply were not issues. For the homeowner, it was a devastating loss because of the heat and smoke damage throughout the house. What makes a detailed AAR worthy is that very little water [five gallons per minute (gpm)] successfully suppressed the free-burning and self-vented fire and the incident is a good example of how understanding modern fire dynamics can lead to the development and effective application of modern tactics.

The fire originated in the sofa in the living room at the front of the house. The female occupant was lighting a candle and dropped the match onto the sofa. By the time she returned from the kitchen with a container of water, the couch was well involved. She immediately exited the house and called 911. The police arrived first and reported to dispatch that the occupant was alone in the house, had safely exited, and was standing across the street.

West Haverstraw is a typical suburban community served by a well-trained, well-staffed, and well-equipped fire volunteers. The fire scene was very close to my house, and the fire station is on the other side of a very bad traffic pattern, so I went directly to the scene. I carry a clean set of gear in my car.


When I arrived, heavy fire was venting through the front window from the now fully involved living room. The fire had apparently completely failed the window on the A side of the house near the A/B corner. My 360° report confirmed that the home’s other windows and doors were closed. There was no indication of fire involving other parts of the house. The police officers had the occupant across the street and confirmed that she was the only one home at the time of the fire.

Firefighter Brian Sullivan from the Stony Point (NY) Fire Department was returning in the chief’s car from a mutual-aid fire and had his turnout gear and self-contained breathing apparatus (SCBA) with him. He was applying water through the failed window into the fully involved living room with a garden hose when I arrived. This certainly is not the best way to deploy firefighters, but the priority was to attempt to save the occupant’s home. Flames were pushing out of the window, and the homeowner was watching her house being destroyed before her eyes on a nice summer evening. Fire continued to vent from the window. Surely, she did not care who was going to extinguish the fire or how. Saving her home from total destruction was paramount. The goal was to extinguish the fire sooner rather than later. What would you do if it were your neighbor’s home?

Since I did not have my SCBA and Sullivan had his, the plan was that I would continue to apply water while Sullivan masked up on the porch and then I would pass the hose to him, making sure that the door would be opened only enough to enable Sullivan to grab the hose and then closed quickly to limit air flow to the room.

Getting the nozzle from a firefighter when he is applying water to the fire is always a challenge. As I continued to put a few gpm from the garden hose on the fire, the fire was darkening down to everyone’s amazement, including the bystanders, who were screaming that we were not going to do any good with that little hose. I thought that maybe they were correct, but water on the fire is always a good option, and now the fire was substantially knocked down. Certainly, the continuous size-up at this point was “doubtful that it will hold”; it clearly was a very tenuous situation. We could hear the siren from the first-due engine coming down the street.

When Sullivan was ready, I handed the nozzle to him and opened the front door. He crawled in the hall and made the immediate left into the living room while I fed him line from the door position. Like any fire attack hoseline, this one kinked. I thought it ironic that I was chasing kinks on a garden hose being used as an interior attack line.

Sullivan skillfully applied water while I held the door mostly closed. He continued his excellent, determined, and skillful work with the garden hose now on the inside of the burning living room. I kept an eye on conditions trying to make sure we weren’t missing anything. I continued to be surprised at the effectiveness of the attack. One of my major concerns was that the fire would travel and light up over Sullivan’s head and up the stairs in the dense flammable smoke, but that never happened. Conditions were improving dramatically. Despite our apparent success, I was wishing that the garden hose were a 1¾-inch line with a solid bore 15⁄16-inch tip flowing more like 180 gpm than five gpm!

In this short but busy time, the fire went from free burning and venting out the window to no visible flames. Smoke had changed from black to white, and the speed of gases venting had decreased dramatically.

Sullivan had almost all of the fire knocked down with the garden hose when the 1¾-inch line from the first-in engine made it to the front door. The engine crew bled the line, masked up, and took the line in to back him up. By this time, there were two in/two out with the engine crew in reserve. After command saw the line charged, he communicated with the outside vent team, which took the windows on the B side. After applying a few gallons of tank water, that line was immediately shut down as well.

Lessons Learned and Reinforced

The amount of air/oxygen available to the fire is a large factor in the fire’s growth and spread through the house. The fire created only one bidirectional vent—the heat-failed window. This allowed the continual free burning of contents in the living room. The fire did not spread toward the rear of the living room, probably because of a lack of oxygen. The couch fire likely was consuming the oxygen entering the lower portion of the failed living room window. Since there were no other windows or doors open, there were no flow paths to facilitate the fire’s spread. The mixing of flammable smoke with air being let in the mostly closed front door did not light up and flash up the stairs as was feared.

Captain Bill Gustin, Miami-Dade (FL) Fire Rescue: Historical Perspective

“Veteran firefighters have experienced fires that were all but totally extinguished by a neighbor who stretched a ‘green line’ to a bedroom window. When you think back, in many cases the bedroom door was closed, limiting the supply of oxygen, thus keeping the fire within the suppression capability of a green line.

“Recall the many articles published on the use and effectiveness of ‘the can.’ What does the Fire Department of New York teach its probies? Use the can to knock down incipient fires. If the fire has intensified past the incipient phase, use the stream of the can as a shield so you can close the door to the fire room—again, limiting its oxygen supply.

“When I first started riding with my dad in Chicago, there was no such thing as a fast attack with tank water; everything was a ‘lead out,’ a reverse lay; there was no water in any hoseline until the engine had connected to a hydrant and pumped it. While waiting for water, firefighters would operate several five-gallon ‘hand pumps’ through a window on the fire. Their success depended largely on whether the door to the fire room was open or closed.

“For petrochemical-based synthetic materials (that would be just about everything in a modern American household) to convert the potential energy locked up in their polymer molecules into heat energy, they would have to be mixed with oxygen in a chemical reaction we know as ‘combustion.’ Simply put, the more oxygen available, the more of the polymer molecules can be converted to heat energy. Conversely, limit the supply of oxygen by closing a door, and it will limit the amount of heat energy that can be produced.

“Since the occupant had the presence of mind to close her front door and it was kept closed, the fire in the living room had only one intake and one exhaust—the window from which the green line’s stream was directed. As correctly stated, since there was only one opening, there was bidirectional flow; relatively cool air flowed into the bottom of the window while heat and fire gases (flames) vented out of the top. The line of demarcation? Yup, that’s right, the neutral plane. I believe that the limited ventilation opening, just the one window, made the fire ventilation limited, deprived of an adequate supply of oxygen. It limited the amount of fuel that could be converted to heat energy, and much of the energy was being absorbed by the green line. The firefighters’ actions stole heat energy from this fire and limited its intensification.”

Chief (Ret.) Daniel Moran, Suffern (NY) Fire Department: A Chemist’s Perspective

“I view this as a chemistry experiment with the fuels; oxygen available; and liberated heat, smoke, and water as reactants. In a chemistry experiment, you put the reactants in a beaker, stir them up, and a reaction will occur. The result of mixing these ingredients, just like your favorite kitchen recipe, in the proper or improper proportion or sequence will determine what the outcome will be.

“The garden hose flowed similar (small, very small, five gpm) amounts of water as a residential sprinkler, compared to our 180-gpm target flow for handlines. We all profess the importance and reliability of limited water from a sprinkler, but because the green line did not come off the big red truck, we tend to discount its effectiveness. We need to understand residential fire dynamics and the ingredients/reactants in this equation in equal proportions to our burning desire for 180 gpm from a 1¾-inch line. Of course, I am not suggesting a garden hose fire attack with five gpm is sufficient. It was the quantities of the reactants at this fire that were critical to the success of the green line.”

Tactical Considerations

Following are some of the crucial tactical considerations for success at these fires.

Sending in search teams before water is applied is extremely dangerous, especially if working above the fire.

Traditional tactical search doctrine would have sent the interior search team in before the hoseline. The team members would have dutifully chocked the front door open, creating a flow path that provided oxygen to the flammable and very hot smoke throughout the house. This inflow of oxygen, when mixed with the flammable products of combustion, could cause the room to light up and maybe extend fire up the stairs. At this fire, as the garden hose and then the 1¾-inch line were moving through the door, the door firefighter kept the door closed as much as possible to further limit the inflow of air.

The 2010 UL report “Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction” describes an important tactical consideration of residential fires succinctly in the executive summary:

“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. Taking 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 the one-story house and 200 seconds for the two-story house. In many of the experiments, from the onset of firefighter untenability until flashover was less than 100 seconds. These times should be treated as being very conservative.

“If a vent location already exists because the homeowner left a window or a door open, then the fire is going to respond faster to additional ventilation openings because the temperatures in the house are going to be higher. Coordination of the fire attack crew is essential for a positive outcome in today’s fire environment.”

The implications for the survival of our search crews and the need for effective engine company operations are obvious. Horizontal and vertical ventilation must be coordinated to occur when, not before, water is being applied to suppress the fire. Command directed the Bravo-side window to be taken after the 1¾-inch hoseline was in place and flowing. This improved interior conditions, as the fire was almost completely suppressed and did not provide the fire with the needed oxygen to spread to other areas. The home suffered heat damage on the first floor but, as already mentioned, conditions for fire spread in those areas were not present. It appears that lack of oxygen was the key factor.

Heat release rates from modern furnishings are very high.

There was significant heat damage to plastics in the rear of the living room and kitchen toward the rear of the house. Additionally, there was intense heat upstairs, as reported by the teams checking for extension on the second floor and attic. Smoke was banked down to the floor during the fire attack, and smoke staining was strong down very low on the walls throughout the house. All that remained of the couches were springs and remnants of the wood framing on the ends. Despite its size and five gpm, the garden hose stream was able to reach the burning fuel and control the fire.

We should bear in mind that in cases like this where there is only one (and in this case, a relatively inefficient) vent point, most of the flaming combustion is happening outside the building. Inside, the combustion is incomplete and may be controlled with relatively little water. Strategically, we must expect residential fires to go to flashover in a short time, especially when active flow paths are present. The key to effective fire control in a modern fire environment is to limit the air supply into the building and flow effective and decisive water to the seat of the fire as quickly as possible.

You don’t need a lot of water for a contents fire in a home.

A very limited amount of water contained this fire. For most residential fires, your 500 gallons (and often more) of onboard water will knock down a significant amount of fire when properly applied and coupled with well-coordinated ventilation. This may be especially important during operations that necessitate aggressive searches for trapped occupants. Engine companies will best support search teams with rapid and decisive amounts of water at the seat of fire to ensure improved conditions and faster advancement of search crews.

Of course, the effectiveness of tank water is not an excuse not to establish a reliable water supply. This fire and others like it (ventilation limited) provide some scale and insight as to how you may be able to best use available resources such as your first-in engine company and situations that may be further complicated with limited staffing on your first-due engine and delayed response from second-due engine companies.

As UL reported based on 25 live fire suppression scenarios in its report “Impact of Fire Attack Utilizing Interior and Exterior Streams on Firefighter Safety and Occupant Survival” (page 187):

“When dealing with a room-and-contents fire, the energy release rate is limited by the available oxygen (ventilation limited) [13,14]. It does not take a large amount of water to absorb the energy being released and knock back the fire. Although less is not necessarily better, when a water supply has not been established, or in areas where no municipal supply exists, water application should not be delayed to establish a water supply. Even a 500-gallon supply tank can be sufficient to knock back two rooms of fire if the attack crew can get the water where it needs to go.

“During the 25 suppression experiments conducted, utilizing a 1¾-inch handline flowing 150 gpm to 165 gpm, the most water used for initial knock back and suppression was less than 250 gallons. When attacking a single room-and-contents fire in a residential structure, knock back and initial suppression are often possible with less than 100 gallons, in some instances less than 75 gallons. Even flowing while moving to the compartment of origin did not result in using more water than available in a 500-gallon supply tank.”

Assemblies that resist fire insult are excellent at containing contents fires and limiting damage.

Like most homes, this one had an open and unenclosed stairwell. Stairs were directly behind the front door and directly adjacent to the fire room whose burning contents were about six feet away. The legacy construction had wall coverings of plaster over rock lath. Even after the application of water, the wall coverings held. Fire never entered the wall cavity, which would have caused much more than damage to just the contents.

Legacy construction had associated with it the classic “20-minute rule.” We were taught we had 20 minutes of firefighting time for an interior attack before structural weakness from fire impact was a concern. Many experienced firefighters are familiar with this rule and passed it on during training sessions.

Modern residential construction such as engineered lumber and trusses and lightweight unrated drywall systems may not withstand a fire’s assault for nearly that long.

Chief Peter Van Dorpe, Algonquin-Lake in the Hills (IL) Fire Department: Tactical Considerations

“Old-school firefighters who had a lot of experience with fires in balloon-frame buildings would say, ‘Always check the basement first’ regardless of where the fire is showing. The reason is very practical: Balloon-frame buildings were built with hundreds of interconnected void spaces that could hide a lot of fire. A fire in a balloon frame showing out of the attic might easily have originated in the basement and could break out around you at any time. We would do well to apply this lesson universally at our firegrounds. Always check the basement—that is, make sure you know what is going on below you and over your head before you make your push. On the modern fireground, a fire that has entered or, worse yet, has originated in the void spaces is a very different and much more dangerous animal than a room-and-contents fire. Come prepared for the fight.”

For additional background and facts, refer to the UL report “Improving Fire Safety by Understanding the Fire Performance of Engineered Floor Systems and Providing the Fire Service with Information for Tactical Decision Making” by Steven Kerber and Daniel Madrzykowski. The executive summary states in part: “There are several tactical considerations that result from this research that firefighters can use immediately.”

We all strive to learn something from each run. In this case, this routine house fire provided us with valuable insights into the practical application of modern house fire dynamics, ventilation, and suppression techniques.

Author’s note: Thanks to Chief Peter Van Dorpe; Captain Bill Gustin; Dave Walsh, chair (ret.), Dutchess (NY) Community College Fire Science Program; Dan Moran, Rockland County (NY) deputy fire coordinator; Firefighter William Quinn, Westwood (NJ) Fire Department; and Chief Kenneth Patterson, West Haverstraw (NY) Fire Department for their contributions to this article.

JERRY KNAPP is a 42-year firefighter/EMT with the West Haverstraw (NY) Fire Department and a training officer with the Rockland County Fire Training Center. He is chief of the hazmat team and a technical panel member for the Underwriters Laboratories research on fire attack at residential fires. He authored the Fire Attack chapter in Fire Engineering’s Handbook for Firefighter I and II and has written numerous articles for Fire Engineering.

No posts to display