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One of the best and most popular uses for a thermal imager (TI) is during overhaul. A TI can be a blessing to you in determining how far a fire may have extended. Using a TI for overhaul, however, can also be challenging and frustrating, if you don’t understand what areas truly need overhaul. So, what value does a TI bring to overhaul?
First, thermal imaging technology helps identify hot spots that you may otherwise miss. When I say hot spots, I really mean warm spots and when I say warm spots, I really mean warmer-than-cold-spots. Why is this important? Because many firefighters have become quite adept at locating and overhauling those spots that are obviously hot; however, the TI can determine temperature differences as small as 1/12th of a degree Fahrenheit, giving you the ability to determine temperature differences that truly indicate whether a smoldering rafter has been “extinguished.” This sensitivity reduces the likelihood of a rekindle and additional property loss as well as saves you the embarrassment of having to put it out again.
Second, by identifying specific areas of concern, you can limit your overhaul efforts to true areas of concern. In certain instances, entire sections of wall may be saved by proper use of a TI. Last, by guiding firefighters promptly and specifically to hotspots, firefighters spend less time on scene and do less work. This reduces the chance of injury and places companies back in service sooner.
Depending on the type of TI you have, you can rely on one of at least three functions that can help you assess temperature differences in an object or area: colorization, temperature indication and change in the TI’s sensitivity or gain mode. Let’s look at these most common aids:
• If your TI has hot-spot colorization, hotter objects will be shown in color. In overhaul, depending on the temperature thresholds for color activation on your TI, you can identify hotter objects as they will often appear as a certain color. On some TIs, this mode is manually activated so that you can control the threshold at which the color activates, helping to isolate hot spots.
• Most TIs today have a temperature indicator. Make sure you understand its uses and limitations. By comparing the temperatures of various surfaces, you may be able to identify sections of walls that deserve additional attention during overhaul.
• All microbolometer-based fire service TIs use at least two different gain modes. When a TI switches modes, it is often noticeable. This mode switch indicates that the TI has changed sensitivity levels. Most TIs change to lower sensitivity levels when something in the image is very hot, enabling the TI to show detail of higher heat objects. This mode switch is usually accompanied with an image freeze (the firing of the TI’s shutter). The image freeze and the change in sensitivity are indicators that a significant hotspot remains in the scene.
The more skilled you become with the appropriate function(s) on your TI, the easier overhaul becomes. For instance, one fire department responded to a call at a house struck by lightning. The initial investigation revealed an electrical outlet with scorch marks around it. A firefighter examined the wall using a TI, and the TI identified a white line running up the wall. Since this white line ran past the outlet, the firefighter took it to be a smoldering electrical line. He and his crew felt they had found a hidden electrical fire and promptly opened the wall from floor to ceiling.
The white signature shown on the TI was nothing more than a hot water pipe feeding a radiator on the second floor. The electrical line was only damaged in the outlet box; there was no fire running up the wire. A better understanding of what the TI was showing by using the function(s) described above along with traditional overhaul techniques might have saved the homeowner money and spared some embarrassment.