Original Post found at: http://chicagofirewire.com/maintaining-aggressive-culture-science-mind/
Research on modern fire dynamics and different fire ground tactics is a hot topic throughout the fire service for a multitude of reasons. Traditional cultures being at the forefront. Many folks in the fire service today, whether your tenure is on the order of 5 or 25 years, have known nothing other than the “aggressive interior attack” as a means of fire suppression. If you look back at firefighter training literature from the 70s/80s (our predecessors in the fire service), members were taught to cool the environment prior to making entry from the safest and most effective location possible. This could be from the exterior or from an adjacent area to the location involved in fire. Why? Because turnout gear and SCBA’s were not widely used. Therefore, in order to make entry and complete suppression, the environment had to be cool enough for firefighters in denim coats. See the below picture from IFSTA 200 in 1977.
What happened when turnout gear and SCBA’s became the norm? The fire service turned to a culture of aggressive interior firefighting, and rightfully so! This was a safe practice for many years as the natural fuels and furnishings within buildings didn’t react as quickly to fresh air via ventilation openings. This bought the crews time to make entry and find the seat of the fire to extinguish. Unfortunately, the times have changed and the tactics are playing catch-up. Modern fuels experience quicker growth phases and often lead to ventilation-limited conditions prior to FD arrival. This can cause RAPID and EXPLOSIVE growth in a matter of seconds when ventilation openings are made by arriving crews. This leaves the aggressive interior attack crews in trouble as they scramble to open up the line and flow water. Is the research saying no more aggressive interior attack? Absolutely NOT. A transitional attack is simply a quick exterior knock on fire showing upon arrival, followed by making entry to complete extinguishment. Doors still need forced, searches still need to be completed, and an interior firefight still needs to be conducted. This is simply another tool in the toolbox to be employed WHERE APPROPRIATE to conduct a safe and effective firefight for both the occupants involved and responding personnel.
Attached garage fires are a PRIME example. The only fire barrier found in residential homes with attached garages is the common wall and doorway separating the garage from the rest of the home. It’s widely accepted that for an attached garage fire, crews should make entry and conduct fire attack from the interior of the home via the doorway to the garage. It is a common belief that attacking the fire from the exterior would push heated fire products throughout the structure, endangering the home occupants. See the below pictures and video links.
Interior Garage Attack
Exterior Garage Attack
The two videos are of nearly identical residential structures with an attached garage. The fires are started in the garage and allowed to reach flashover conditions. The doorway to the occupied home is closed in both cases. One video shows an interior attack where you can see how breaking the barrier between the garage and the home causes conditions within the structure to greatly deteriorate. The other video shows an exterior attack where the doorway to the home is left closed with drastically different results. The pictures show a fire near Wake Forest where which started in the attached garage, reached flashover conditions, and extended up the front of the home. The doorway to the garage from the home remained closed throughout the duration of the incident. You can see the results.
Now you ask, what would have happened if the doorway was open upon fire department arrival? Wouldn’t a quick exterior knock push smoke and fire into the home endangering the occupants? With the use of a straight stream or smooth bore nozzle, absolutely not. When applying water through an exterior opening (window, doorway, garage), via a straight stream or smooth bore nozzle, the stream makes contact with the ceiling just inside the opening, creating a broken pattern which hinders fire growth, lowers temperatures within the compartment, and suppresses the fire. It is critical that the stream does not occlude the opening which allows it to remain a bi-directional flow – serving as both an inlet for the fresh air and water application and outlet for the heat fire products and smoke. If the straight stream or smooth bore nozzle were “whipped” around, or if a fog pattern were used, the pattern could occlude the opening which once served as an exhaust. This would prevent the heated fire products and smoke from exiting the opening and cause the pressure within the fire compartment to increase. This can cause a “push” of heated fire products and flames to a low pressure vent somewhere else within the structure. Remember that not only a fire increases pressure within the compartment, but the application of a fog stream can as well. High pressure ALWAYS moves to low pressure. Water does not push fire, but changes in ventilation and the flow path certainly can. Therefore, COORDINATION IS KEY! Research has shown time and time again, the appropriate application of water into a fire compartment (straight stream or smooth bore off the ceiling close to the opening), regardless of interior or exterior position, drastically improves conditions throughout.
Take the few minutes and visit the UL Firefighter Safety Research Institute (http://ulfirefightersafety.com/) and the National Institute of Standards and Technology Fire Fighting Technology (www.nist.gov/fire) webpages for information on the MULTITUDE of tests conducted in real structures. The information is out there. Educate yourself and become a modern firefighter that understands the need to stay progressive. Line of duty deaths need to stop now.
About the author:
Keith Stakes is a Fire Protection Engineer with the National Institute of Standards and Technology where he studies the effectiveness of fire fighting tactics and fire ground operations. Additionally, he is a Fire/Rescue Lieutenant with the Bethesda-Chevy Chase Rescue Squad in Bethesda, Maryland. He serves as the Chairman to the Fire/Rescue Policy and Operations Committee as well as a lead instructor for the department. Keith holds both a Bachelor’s of Science Degree and Master of Engineering Degree in Fire Protection Engineering from the University of Maryland, College Park. He manages the Squad Jobs training page on Facebook as well. Keith can be reached at Facebook | Email