THERMAL IMAGING FOR THE FIRE SERVICE, PART 5: TACTICS FOR FIRE ATTACK
BY STEVEN P. WOODWORTH
What we have discussed so far–“The Basics of Thermal Imaging,” “The Electromagnetic Spectrum,” “Thermal Characteristics,” and “Interpreting the Image”–should be enough information to give you a basic understanding of what thermal imaging is and how it works. Yet, this information would be of no use if we could not apply it on the fireground. This article begins the discussions of how to apply this information to the tactical and strategic decisions that must be made on the fireground, fireground tactics, and how the information presented by a thermal imaging device can be used to increase safety on the fireground.
Before the thermal imaging device can be of any use on the fireground, personnel must be adequately trained in its use. I do not believe that there is a fire department in the country that would hire a firefighter and place him in a situation that requires using a self-contained breathing apparatus without first having trained him in its proper use. The same should hold true for thermal imaging devices (unfortunately, this is not always the case). The absolute first objective after purchasing a thermal imaging device should be to have all personnel properly trained in its use. This training should include both classroom and practical sessions during which potential users are shown how to use the unit effectively.
SIZE-UP
Size-up is the process of identifying and evaluating the conditions on the fireground. It begins with the initial dispatch information and is ongoing while companies are operating on the fireground. Now the question is, how do we apply this information to thermal imaging? The information the dispatcher provides is essential to the firefighter assigned the duties of thermal imaging. He must consider the building description and type of construction. Through experience and preplanning, we learn the types of buildings and construction that are in our response territory. Personnel assigned the task of thermal imaging must take this information into consideration. Office buildings made of masonry construction, for example, would limit the ability of the thermal imaging device on the exterior of the structure to size-up. Single-family residential structures tend to be of wood-frame construction. The density and mass of these materials allow the thermal imaging device to be used on the exterior of the structure to determine the fire`s location.
Thermal imaging devices are extremely useful in determining fire spread in buildings of wood-frame construction. The device may be used to determine how effective tactics and strategy are. My experience in the average residential structure has been that if I can see that the thermal layer is building down below the top of the windows and the building has been ventilated, the ventilation hole is not being effective. This may be due to the fact that the attic is divided, the ceiling was not punched out, or the hole simply is not large enough for the area being ventilated. The thermal imaging device will show whether not enough water is being applied to the fire or the stream is not penetrating the fire. This information can then be passed along to Command, and the strategy can be adjusted accordingly. Command can now have additional lines brought to the area where they are needed or lines may be relocated for more effectiveness.
Oftentimes, in fires in larger buildings such as warehouses or in buildings subdivided into smaller areas such as high-rises, advancing hoselines to the fire is met with great difficulty. First, the location of the fire must be determined. The thermal imaging device can be extremely useful; one person can simply scan the area and identify either the fire or the general direction of the fire, depending on the level of the thermal layer. On entering an area, the firefighter operating the thermal imaging device should always use a six-sided approach while scanning. Scan from the extreme left to right at the floor level, looking for victims. Then scan from the extreme left to the right at the ceiling level and the floor, looking for fire conditions and structural integrity.
The thermal imaging device can also be useful in avoiding obstacles while advancing hoselines. It can help determine the shortest stretch to the fire, thereby reducing stress on the attack crew.
The fire service has had much debate over whether the fuel load in buildings today is causing hotter fires than those of 30 years ago. While the fuel load has changed, the debate seems to be over whether Thorton`s Rule applies and therefore whether fires are burning hotter. My personal opinion is that fires are burning hotter and that this is part of the reason that firefighters all across the country are dying in flashovers.
PREDICTING FLASHOVER
Just as technology has increased the hazards firefighters are now facing, it has also provided solutions to some of the problems. While flashovers are happening more frequently, our ability to predict them has improved tremendously. The thermal imaging device can be used to more accurately predict flashover. As discussed in my previous article on thermal contrast, as heat builds in a given area, the entire area will eventually appear white in the image. This is due to the fact that there is little or no thermal contrast. This may appear in an attic or room. Prior to flashover, the thermal layer will appear to have a distinctive movement, which can be described as “water flowing in a creek.” Obviously, the image is of the superheated fire gases. If allowed to continue, flame may be seen starting to lick through the thermal layer. At this point, water should be applied or a hasty retreat made, since flashover is imminent. As flashover occurs, the firefighters operating the thermal imaging device will lose vision. This is due to the fact that there is no longer any thermal contrast in the area. The firefighter operating the thermal imaging device should direct the unit across the floor. If there is any thermal contrast, it will be down low. This might enable the operator to identify any exits or hoselines leading to exits. The firefighter using a thermal imaging device to predict flashover must also consider the construction of the building and contents. Flashover in smaller areas will tend to happen more quickly, since the heat has less of an area in which to build up. The operator must realize this and continuously check the ceiling level for heat buildup.
When possible, the operator should try to identify a place on the wall, such as the top of the window frame. This will give some indication of how far down the thermal layer is and how fast it is building. Larger structures with wide-open areas will require more time for the heat to build up. When large amounts of heat are developing rapidly in these areas, withdrawal should be considered. There obviously must be a large fire producing the heat, or a large amount of fire is in a concealed space. In either case, the operator must consider the amount of time it will take to withdraw the crews from the area. In addition, large open areas would indicate truss construction; the heavy amounts of heat indicate a large volume of fire and potential collapse. When the heat conditions are developing rapidly, the operator should identify any exits that could be used for egress. Obviously, the best method is to prevent the flashover by accurately predicting it with the device.
The thermal imaging devices in use by the fire service today are very reliable; however, they are still mechanical devices that are subject to failure. Firefighters operating these devices should still use safe fireground practices such as carrying a powerful flashlight, maintaining contact with a wall, and staying in communication with command.
Technology is increasing the hazards faced by today`s firefighters, yet technology can also benefit firefighters. The key, however, is to have properly trained firefighters to operate the equipment. n
STEVEN P. WOODWORTH is a firefighter with the City of Atlanta (GA) Fire Department, assigned to Squad 4. He is an adjunct instructor at the Georgia Fire Academy and a volunteer firefighter for Fayette County. He is co-author of Fighting Fires with Foam (Van Nostrand Reinhold: New York City, 1992).
