The environment known as the fire ground is a dynamic, deadly, and increasingly complex arrangement of almost limitless variables. Firefighters are facing even greater challenges with advancement of lithium ion batteries in homes, cars, and more synthetic fuels being used in the construction and contents of the building itself. It is of the utmost importance that firefighters do not enter a structure without a plan based on training, experience, and fire ground data.
In previous years, firefighters were taught not to open the nozzle until they saw fire because of the following reasons:
- Early water application would upset the thermal balance driving heat downward on potential victims and causing a loss of visibility.
- The fear of steaming a victim laying in this environment.
- To not cause unnecessary water damage.
However, many previous veteran firefighters knew in many cases that there was a threat moving over there heads during fire attack even though it wasn’t visible with their eyes. This concept was known as black fire. In the beginning, firefighters used their senses to detect heat and move towards the heat based on this information. However, in today’s modern fire environment combined with limitations of the human body this practice isn’t considered “the way” to identify the fires location. When Sir William Herschel discovered infrared radiation he found the highest temperature to fall beyond the red end of the visible light spectrum. This area of highest temperature that was not visible with the naked eye was reported to the Royal Society as “Dark Heat” in 1800.
Lloyd Layman stress the importance of understanding the transfer of heat in his book Attacking and Extinguishing Interior Fires:
“Fire extends its boundaries’s by transmitting heat to exposed combustibles and it is of utmost importance that those engaged in fire-fighting activities have a thorough understanding of the fundamentals that govern the transfer of heat.”
And FSRI states in their report “Effect of Firefighting Intervention on Occupant Tenability during a Residential Fire”:
“The effectiveness of suppression actions in extinguishing the fire were dependent on the ability of those actions to
1) cool surfaces in the fire room and
2) wet unburned fuel.
Exterior suppression actions on second-floor bedroom fires resulted in a decrease in temperatures throughout the second floor, followed by regrowth prior to final suppression through interior streams.
When exterior suppression was performed on first-floor kitchen fires, where more complete fuel wetting was possible, regrowth was not observed prior to interior suppression. When surface cooling or fuel wetting are not possible due to the elevation of the fire room, missing ceiling, or obstacles, firefighters should consider alternative means of water distribution to improve the effectiveness of suppression actions from outside the fire room.
Suppression actions, whether interior or exterior, generally resulted in a decrease in temperatures and gas concentrations at locations where occupants may potentially be located. “
Conditions improved most quickly at locations closest in proximity to the inlet of the flow path established between the front door and the fire room. For this reason, opening an exterior door to gain access should be thought of as an important ventilation action, both in terms of its potential to cause fire growth and its potential to improve conditions for potentially trapped occupants.”
In short, we remind the public each year to water their Christmas tree to prevent a possible fire but firefighters fail to water the couch as they pass this potential fuel source that is rapidly off-gassing highly flammable vapors.
But there are many firefighters who are opening the nozzle on the way to the fire but our research has shown that the majority of these fire suppression efforts are brief short Burts or penciling techniques. In addition to this information, penciling has been disproven as an adequate cooling method in three different research studies. It also should be emphasized that the concept of “penciling” was borrowed from our friends overseas and US firefighters improperly applied the concept in order to “control” a flashover container environment. Once again, a concept misinterpreted and not properly applied is not only dangerous but can be deadly.
Why American Firefighters Should Not Pencil?
Tactical Thermal Imaging allows firefighters to direct their streams more efficiently toward where the water is needed most rather than all over or missing superheated areas. In many cases, of watching firefighters on standard training fires we have noted that firefighters only briefly open the nozzle before advancing and there is often temperatures of 800-1000 degrees still behind them. A trained crew leader can guide the efforts of the stream and ensure that superheated areas are “erased” and not merely penciled.
The Ineffectiveness of Burst Suppression:
At 3 ft above the floor, where the firefighters are operating, the temperatures decreased an average of 20% immediately after burst suppression (starting temperatures averaged 160◦F). This decrease is a combination of cooling from the water flow and the cool air being entrained by the fire.
However, temperature rebounded within seconds and the cooling was not sustained!
At 7 ft, above the firefighters’ heads, the temperatures averaged 360◦F and decreased an average of 10% after burst suppression and also recovered within seconds.
There was NO impact on temperatures in the hallway and the firefighters did NOT report feeling any change in thermal conditions as a result of the burst suppression.
While lasting cooling did not occur, using the short burst of water, there are other potential benefits of flowing once inside the structure when you have zero visibility: to wet walls and ceilings to potentially slow down ignition of the gases and wall linings in the room; and to hear water hitting walls and ceilings to get an approximate size of the space when there is no thermal imaging camera available. This can be important in the case of vaulted ceilings to let the crew know that there is potentially a high volume of unburned smoke over their position.
Direct quote from “Effects of Different Suppression Tactics on the Firefighter and Compartment Environment”
The thermal rebound effect can be seen in this video and many of our other videos on our YouTube channel when the fire attack crew shuts down their nozzle while advancing the line. Watch how quickly the heat rebounds and passes over them.
What about disrupting the thermal layer?
This quote from Manny Barrajas Jr states it well:
“Pressure moves from high to low and introducing a stream that will not disrupt the thermal layer but penetrate and do away with it, low air entrainment volume and a reduction in temperature that creates gas contraction makes for an effective fire attack. This can only be accomplished with a solid stream or straight stream continuously flowing or with minor interruptions in the worst case situations.
Our attack creates a high pressure front that brings in fresh air to fill the negative void behind our stream. As this occurs we get a lift of hot gases (gas contraction) when cooled that retract smoke as well as a decrease in temperature that offers the unprotected civilian a chance at surviving.
By definition, if it’s good for them then it’s good for us. This form of fire attack is the most ethical way of firefighting that currently exist.”
It is quite interesting to note that the same teachers that instruct firefighters not to open the nozzle until they reach the fire room for fear of upsetting the thermal balance actually allow temperatures to increase while making their “fire attack” and when they finally do open the nozzle the steam conversion is much higher due to the higher level of temperature and pressurization within that confined space.
The “thermal balance” was originally taught not to be disturbed by firefighters who did not have the luxury of an SCBA (or B.A. for my friends overseas). They wanted to keep the lower air track clean for victims and for themselves as they advanced toward the fire. The problem with the phrase “thermal balance” is that the heat doesn’t stay balanced. It is gradually descending, cooking, and killing anything under neath its power. It can be compared to a broiler. This imaginary line in our eyes is clearly visible through the eyes of a thermal imaging camera (it is manufacturer dependent upon when it is visible and at what specific temperature it is colorized). This thermal layer is actually deleted by early water application causing less thermal upset and a more gradual cooling rather than a more violent effect by those who choose to wait to open the nozzle at the fire room.
What about steaming the victim?
Facts to consider when a firefighter fails to cool the environment:
- At 131 Degrees Human Skin burns producing a second degree burn.
- At 162 degrees Fahrenheit, human skin is destroyed.
- Once the heat source is applied to a victim, 35% of the burn damage occurs AFTER the heat source is removed**(See Alice Stoll’s work on the Stoll Curve)
- When Superheated areas are cooled, Steam WILL be produced but gas contraction is greater than steam expansion.
- When superheated areas are NOT cooled, firefighter PPE begins to saturate with energy diminishing the thermal protective performance of their PPE if a flashover or a rapid fire development event occurred.
- For every time 1 degree Fahrenheit is doubled Radiation increases exponentially by the 4th power!
- Between 187-212 degrees of superheated gases inside a victims trachea has shown to cause fatal respiratory burns.
FSRI report on the Impact of Fire Attack Utilizing Interior and Exterior Streams on Firefighter Safety & Occupant Survival states:
“As the moisture was measured at higher elevations in the space, more moisture was detected. Even prior to suppression, at elevations in the smoke layer (5 ft), water vapor increased by a factor of 2.
When the measurement was taken at the 1 ft level there was limited increase in moisture content between 5 seconds prior to suppression and 60 seconds after suppression. At the higher elevations in the space (in the smoke layer) the moisture would increase between approximately 2% by volume during the period between 5 seconds prior to and 60 seconds after suppression however it would increase by a similar amount from ignition until the time of 5 seconds prior to suppression.
This suggests that at the 1 ft level in a bedroom outside the flow path, where water is not applied in the room, moisture content is not increasing during suppression activities. At the higher elevations, moisture content is increasing however it is not possible to determine whether the increase is due to the application of water or due to transport time for the products of combustion to reach the location of the sensor.
With no appreciable increase in moisture content at the 1 ft level even after suppression, it is not possible the suppression is causing a victim further damage due to steam. “ (p.199)
As stated in recent post:
“Quit worrying about water damage and start worrying about people damage.” Multiple Calls Podcast.
Firefighters need to understand that our efforts should be improving conditions. Proper water application applied early and consistently moving towards the seat of the fire reduces overall temperatures, increases chances for victim survival, and reduces the risk of rapid fire development.
But what about causing unnecessary water damage?
It is interesting to note that the same instructors that taught me to not flow too much water during fire attack would consistently use numerous booster tanks of water on the same building during overhaul. When I questioned this methodology, the response I received was simple yet contradictory “We don’t want a rekindle.”
The average insurance claim for a home fire was over $40,000 and if more than 15% of the home was damaged all the Sheetrock is required to be removed according to the US Insurance Institute.
Firefighters should be concerned about unnecessary property damage. But this would be better achieved by more efficiently and quickly extinguishing the fire through proper water application efforts towards the fire rather than blindly throwing water into the darkness hoping we hit the target. A sniper doesn’t close his or her eyes just before they take the shot; neither should a firefighter be deprived of seeing the effects of the enemy known as fire and aggressively reducing the heat on the way to the fire.
This is Intelligently Aggressive Fire Attack.
Insight Training LLC
Thermography Certified Fire Service Professionals