A new firefighter’s introduction to fire behavior has traditionally been an apprenticeship. The firefighter cadet learns the very basics during a three-hour class in Firefighter I — the expectation is that they will learn everything else about fire behavior alongside a senior firefighter in the field as they battle fires together.
There’s just one problem with that: the number of fires each year has declined and continues to do so. So the experiential aspect of a firefighter’s development has become more limited while the risks of not understanding modern fire behavior have taken quantum leaps forward.
In the late 1970s, firefighter deaths due to traumatic fireground injuries happened at a rate of 1.8 deaths per 100,000 fires. By the late 2000s, the rate of firefighter deaths had risen to 3.0 deaths per 100,000 fires. This trend is made more disturbing by an NFPA report from 2010 shows that while the rate of firefighter deaths was rising, the number of structure fires for the same period had declined by 53 percent.
Better fire prevention, building codes, code enforcement, and more fire suppression systems, especially in residential structures, have done their job to reduce the number of fires.
But the declining number of structure fires — and less opportunities to learn about fire behavior first hand — only provides one facet of the threat to firefighter safety during fire control operations. Over the last 40 years the fireground itself has changed dramatically.
A different enemy
The fuel loads in residential structures are one of those changes. Today’s homes are constructed and furnished with synthetic materials — materials that burn faster, deplete the available oxygen in a space more quickly and generate more unburned hydrocarbons.
The way that homes are constructed and the materials used in that construction also have changed. The engineered lumber and lightweight building construction techniques do not maintain their structural integrity when exposed to fire like the old dimensional lumber used prior to the 1970s.
The technology available today to fire behavior researchers like those at National Institute of Standards and Technology and UL gives them an unprecedented ability to measure all aspects of a fire’s behavior including temperature at various levels in a space, air flows within a space, infrared imaging within a space, and video recording and editing capabilities that brings all the data together.
And this is critical to firefighter safety. While anecdotal evidence has been telling us for years that the fireground has changed, we’ve now got the empirical data necessary to make data-driven decisions about how we train and how we tactically approach suppressing fires.
A common theme in NIOSH investigations of firefighter line-of-duty deaths is that the survivors report, “Upon our arrival we only found smoke showing.” Those survivors, and those who lost their lives in the incidents, believed that they were encountering the fire in its growth phase.
Instead, they were arriving with the fire was already in its decay phase. The fire had consumed the available oxygen and the space was now filled with gaseous, heated fuel that was just waiting for additional oxygen to be introduced into the space. These are ventilation-limited fires.
Oxygen starved
That’s why the next event that typically happened was that the firefighters vented a window or opened a door, the fire got the oxygen it craved and —whoom — it grew to a fire of major proportions with a rapid release of heat and an equally rapid rise in temperature in the space in a few short minutes, or even seconds.
Crawling down a smoke-filled hallway in an attempt to locate the seat of the fire must become a thing of the past. Today’s firefighters are advancing not through smoke that’s primarily composed of the products of combustion, but rather through smoke that’s laden with superheated unburned hydrocarbons — gaseous fuels — headed for the nearest source of oxygen.
Increasingly, the fire triangle of oxygen, heat and fuel comes together behind that advancing fire crew, cutting off their means of egress and trapping them in a highly volatile environment.
I’m trained as a hazardous materials specialist, and as such was taught that all tactical operations at a hazmat incident must be predicated on the science of three things: the product, it’s container and the environment.
- What is the product; what are its characteristics; how does it react with other substances?
- What are the container’s characteristics? Has it been damaged, and if so, how has the damage affected its integrity?
- What affect does the environment have on the product and responders?
This is just a synopsis of managing a hazardous materials incident. However, it’s useful to help understand how our approach to structural firefighting must change based upon the emerging science.
The new truths
Fire behavior research is going on around the globe and here in the United States the most prominent and publicized research is being conducted by National Institute of Standards and Technology and UL. This research has produced data that clearly demonstrates seven truths.
- Structure fires are most likely in a ventilation-limited state than a fuel-limited state when we arrive.
- Ventilation does not have a cooling effect on a ventilation-limited fire.
- Exterior fire attack is not strictly a defensive tactic.
- Exterior fire attack will not harm victims.
- The best tactic for combating basement fires is not using a top-down approach.
- The long-accepted concept that fire streams push fire is a myth.
- Venting the structure and searching before suppressing the fire is not the best way to improve victim survivability.
NIST and UL have now compiled more than 10 years of fire-behavior data and the results are conclusive. Before making entry into the structure — for either rescue or fire suppression — firefighters must identify and control the fire’s flow path and begin to cool the volatile atmosphere of superheated hydrocarbons.
This is the new paradigm for fire suppression operations in structures.
The research has demonstrated time and again that this new paradigm will contribute greatly to the survivability of any entrapped civilians and the safety of responding firefighters by dramatically reducing interior room temperatures and cooling those volatile hydrocarbons.
SLICE-RS
This paradigm shift needs to take place in both the training and operational venues of the fire service. The International Society of Fire Service Instructors developed the acronym SLICE-RS as a teaching tool for instructors and an operational tool for the first-arriving fire company.
- Size-up.
- Locate the fire.
- Identify and control the flow path.
- Cool from a safe location.
- Extinguish the fire.
These first five are to be done in sequence. Success depends on firefighters and officers completing these tactical objectives safely, effectively and efficiently. The last two objectives — Rescue and Salvage — are considered targets of opportunity to be acted upon at any time in the SLICE sequence.
SLICE-ER addresses two key concepts that have arisen from the fire-behavior research. First, identifying and controlling the flow path is critical to keeping a ventilation-limited fire from attaining the oxygen it needs. Second, cooling the volatile atmosphere from the exterior will rapidly decreasing temperature inside the structure and improving interior conditions for occupants and firefighters.
Beyond these operational changes, the fire service is going to have to retool its entire approach to the “what, why and how” of teaching fire behavior and the associated fire-control tactics. Teaching materials including textbooks must be revised so that we can start teaching both entry-level and incumbent firefighters the new way to do business.
Moving beyond the classroom, significant changes need to occur in how firefighters are taught practical firefighting skills so that they’re congruent with our current understanding of fire behavior.
Teaching new truths
First and foremost, fire service leaders should aggressively move forward with these initiatives within their departments. This means having SOGs congruent with SLICE-RS; educating firefighters, officers and instructors on the SOGs; and enforcing the SOGs.
Second, existing physical training facilities such as burn buildings need to be reconfigured or retrofitted so that firefighters and officers can acquire initial and continuing training on the new SOGs. There are some minimums requirements to achieve this.
Make sure all exterior windows and doors can be properly closed, or the airflow through them controlled, so that personnel can learn and develop fire flow path skills.
Inside, make sure all interior rooms and spaces have doors that can be properly closed, or the airflow through them controlled. This will allow personnel to learn and develop interior fire isolation and fire flow path skills.
Also, have the ability to create visible smoke escaping the structure in a manner, such as through an open window, that replicates the smoke and superheated gases. This is where an initial exterior fire stream should be directed to initiate cooling the atmosphere in advance of firefighters entering the structure for search and suppression operations.
Fire behavior research will continue to focus on data collection and analysis for fires in structures, particularly residential structures, to continue building the body of knowledge in that realm. The research will continue to evaluate what impact new fuels and building construction techniques have on fire behavior in those occupancies.
It is incumbent upon fire chiefs to keep abreast of new research and incorporate those findings that have stood up to repeated testing.
