In thermal imaging, firefighters are trained to recognize areas of concern based on heat. However, areas that are cold, appear cold, or that are dark should not be overlooked. The use of thermal imaging in industry is often used more to look for leaks, air infiltration/exfiltration, and thermal bridging where heat is being lost. This is demonstrated in the following inspection photo (provided by Infrared Training Center) where we see heat loss in the uninsulated portion of the attic stairs.
In an environment where every second counts, firefighters should be aware of areas with lesser temperatures as this is often where many victims are found. In the adjacent image, a dark image is seen on a bed. The firefighter soon discovers that this is a person’s leg.
Many firefighters are taught to search for victims in fake smoke where they heat up rescue mannequins. This can be detrimental to them as they begin to associate a victim with being white hot but when in a superheated environment, the victim will either appear dark or blend in with the background. And when discussing firefighter disorientation, cold areas should be focused on as they may provide the firefighter the information to lead them out of the structure as shown in the hose-line in the following image.
- Consider the variables of the TIC itself and how it affects our interpretation:
Many fire departments today are using older thermal imaging cameras with poor thermal sensitivity or newer cheaper situational awareness TIC’s, which equates to the image degrading when viewing higher temperatures. When the TIC switches from High to Low Sensitivity, it often loses discernible detail in the lower areas (that appear colder but may not be necessarily so). Notice also in the image in this older TIC it lacks discernible details inside the doorway of this area due to its lower resolution and poor thermal sensitivity (greater than 80 mK).
Notice in the second image the firefighter blends into the background as the TIC compensates for the overall heat in the image within the field of view by switching to Low Sensitivity.
And finally, compare the differences between the image below in newer high resolution decision making TIC (image on the left) compared to the older low resolution TIC on (image on the right). Photo courtesy of Max Fire Box.
Next, a fire service TIC has either two or three temperature modes depending on the model as no infrared camera can see all temperature ranges at once. They are often “broken up” or segmented into ranges that the TIC can manage without causing oversaturation. This is demonstrated in one such model (The Scott X380) as shown in the three images below as the TIC progresses from High, Medium, to Low Sensitivity as it encounters more severe temperatures. As the tic switches due to increasing heat, the overall detail in the lower temperature ranges diminishes. Notice in the above image, as the heat intensifies, the TIC switches to Low Sensitivity Mode and the area below the thermal layer loses detail.
In thermography, students are taught an acronym known as FORD that explains this concept. It is critical in capturing a good thermal image for analysis.
FORD: Focus, Range, Distance.
FO: Focus-to produce a clear image it must be in focus. Fire service TIC’s automatically focus on the target reducing the time for analysis by firefighters. Notice how clear the image is below when it is taken in High Sensitivity in relatively low temperatures within the TIC’s effective distance range.
R: Range-To produce a good image for analysis, it must be in the proper temperature range. For example, if the thermographer is analyzing an object that is 100 degrees Fahrenheit, the TIC should be in the lowest temperature range which equates to High Sensitivity in firefighting. This is typically between zero to 300 degrees Fahrenheit. If the object being analyzed is 400 degrees and the TIC is in high sensitivity the image will not be clear and valuable details will diminish. Fire service TIC’s are known as automatic gain qualitative infrared cameras which means they automatically switch from high to low sensitivity when a certain percentage of the pixels within the field of view are above a preset temperature. The TIC will produce the clearest picture with the most discernible detail in High Sensitivity which equates to generally lower temperatures (300 degrees Fahrenheit and lower) and allows for more detail in the image for better decision making. If a firefighter stays low and maintains the TIC in high sensitivity, they will be able to see potential victims, areas of concern, room lay out and more by using this to their advantage. Notice in the image below, the first one is very clear in High Sensitivity but when it switches to Low Sensitivity we lose detail.
D: Distance-Each TIC has an effective range based on its distance to spot ratio and resolution. If the end user is too far away from the target, the image will either blend or wash-out into the background or it will be of such low detail the firefighter will not be able to identify it. As shown in the image below (provided by FLIR) we see three images 100’ away with varying resolutions. As the resolution increases, the image becomes clearer and more recognizable. With lower resolution, the end user is limited in their distance from the target. In 160×120 resolution cameras, this can be as low as 7 feet as the effective DRI range to identify a small child’s hand.
In many cases, certain fire service TIC’s use varying color palettes that can confuse firefighters in believing a certain area is cold. For example, there are TIC’s that use a color palette known as Black Hot where it makes everything hot colorized as black. This color palette was not intended nor designed for fire attack.
However, it is extremely beneficial in searching for lost persons from an elevated position, drone use, helicopters etc. This color palette makes a human figure stand out against the background as in this adjacent image provided by FLIR. Whereas in a fire environment, it would make the hottest area black and the coldest area white which is contradictory to our training. As shown in the adjacent above image, the burn container at this training site is showing dark black which would lead the untrained user to believe this is cold when in fact it is very hot. This particular model calls this application mode: Inverse. It is also known as Black Hot, Reverse Polarity, and other names.
And most importantly, there are many Fire Service TIC’s that show dark or gray areas that are NOT cold. In the following TIC’s gray scale is used up to the following temperatures (photos shown in order of description):
- Drager UCF 9000: In Low Sensitivity, Zero-569 degrees Fahrenheit is all in grey scale.
MSA Evolution 6000: In Low Sensitivity, Zero-999 degrees is all in grey scale.
II. Consider the context of the environment and how it affects our interpretation:
Firefighters cannot predict the environment they will be sent to next. However, they can take many situations and analyze them from a critical thinking perspective to determine the following important points:
- Hoarding Heavy Content Environments: These can be the most challenging fires a firefighter can face. In these conditions, the occupant will leave one or two pathways for their primary modes of travel within that environment. A firefighter who identifies these dark pathways early on can more quickly navigate this environment, locate any potential victims faster, and extinguish the fire faster. The image above shows a clear delineation in the pathway as it was a research burn with heavy content conditions, whereas in the image below from an actual heavy content fire, the pathway may not be so obvious. It may take several scans at a lower height to identify this pathway being cautious not to collapse the pathways as it may be the only access to the victim or the fire.
Rescuing a Victim:
While searching for a victim, many firefighters fail to deploy the TIC or use it effectively. The scan is often done far too fast not allowing the TIC to adjust or compensate for the changing conditions it sees. In addition to this, when firefighters can see they opt to walk rather than crawl placing the TIC in the hottest part of the environment. If the TIC changes to Low Sensitivity, the firefighter loses valuable details that could have led them to the victim faster such as shown in the following images:
A firefighter who stays low and keeps the TIC in high sensitivity longer can see more clearly. As water is applied for suppression efforts, visibility is often disrupted and it can cause a deceased victim to blend in with the background such as in the following photos. The image on the left is when suppression efforts begin and image on the right is after the nozzle is briefly shut down. Notice the victim seems to disappear from the image.
- May-Day Firefighter Down:When searching for a downed firefighter, often the coldest object on them will most likely be their SCBA cylinder. However, in certain situations firefighters have abandoned their SCBA when they ran out of air. Be aware that we should then start training our eyes for dark shapes such as SCBA cylinders, gloved hands, helmets, and boots. The following four photos are four different models of TIC’s displaying how an SCBA bottle appears in a superheated environment while it is being used. The condensation process is colder than the overall environment producing a dark cylinder, regulator line, and in some cases the face-piece appears dark.
The presence of high heat diminishes a TIC’s ability to see objects of lower temperatures that tend to become the same temperature at the background. A quick scan when searching for a missing firefighter would easily overlook this firefighter’s boot in this image.
Also, when we see a dark corner or area though the view finder of the TIC that area should be investigated not ignored! This is when using features such as cold spot tracker, from tics such as the SCOTT X380 or the ARGUS MI-TIC, and keeping the TIC in High Sensitivity allows firefighters to see more clearly and possibly locate down firefighters faster. Victims will often be found by windows, doors, beds, and access paths but trapped or lost firefighters will not often be found in the same areas. Learn to note these areas as of special importance and always remember the fundamentals of our search methods should remain our foundation.
Holes in Floors: If a hole in a floor exists in a residential context with no fire underneath, the area will produce what is known as a cavity effect. This is where IR energy is concentrated and it appears a different contrasting color than the area around it. This is often seen when viewing parapet walls and viewing the scupper drains as they will stand out either light or dark depending upon the background and temperatures. However, this doesn’t mean that we will always see holes in floors.
In uniform temperature environments, where the temperatures are relatively similar the TIC loses the ability to see the differences in areas or objects of similar temperatures. Firefighters can increase chances of seeing these areas by flowing water across the floor and wait a few seconds. The hole or depression in the floor will appear differently.
In summary, the thermal imaging camera has many more uses than just “search & overhaul” as my fellow friend and Instructor Joe DeVito states. And these are but a few examples of how we should note, interpret, and look for areas of cold with the same level of concern as we do areas that are hot. It is a diagnostic tool that is only limited by the training, education, and understanding of the individual holding it. May we continue to stay fundamentally sound in our training and use technology to enhance our efforts so the citizen and our fellow firefighters will benefit from our intelligently aggressive actions.
Instructor Andy Starnes
Insight Training LLC
Level II Thermography Certified]