In January's Firehouse magazine, the thermal imaging training article discussed overhaul tips. The article emphasized the importance of practice in becoming proficient with using the TI in this application. Because a thermal imager can detect a temperature difference of less than 0.09?F (0.05?C), you must become skilled at interpreting images and understanding how a hotspot will appear based on the temperatures of its surroundings
Depending on the type of TI you have, you can rely on one of three tools that can help gauge how hot an object or area truly is. These were identified in the Firehouse magazine article: the manual iris control ("Thermal Throttle"), the temperature indicator and the EI mode. The more skilled you become with the appropriate tool on your TI, the easier overhaul becomes. Proficient use is critical to avoid a real, but embarrassing, situation.
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 hot 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. They expected to be heroes for preventing a fire; instead, they caused unnecessary property damage. The white hot signature the TI had shown them 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. If the investigating firefighters had relied on some traditional techniques, they would have saved the homeowner money and spared themselves embarrassment. They could have felt the wall with the back of a hand. They could have removed the outlet cover and inspected the wire in the box to see if there was charring running out of the box. They could have compared the heat signature to a firefighter's hand to see exactly how hot was "white hot." They could have even started with a small inspection hole, rather than opening the entire wall.
If you are not comfortable with the indicators and tools on your TI, you will be frustrated when overhauling after a room-and-contents fire. After the fire is knocked down, everything in the room will still be hot. As a result, the room will display in shades of white and light gray on the TI. Many times this frustrates firefighters so much that they stop using the TI to assist during overhaul. However, by using the tools and indicators, firefighters can make the TI work properly in this application. Going back to the basics of how a TI functions can also help.
Remember the TI only sees temperature differences. During overhaul, the TI may generate a better thermal image if firefighters introduce some temperature differences artificially. For example, go ahead and open a small section of wall and spray the area with water. This generates significant temperature differences and helps the thermal imager generate a better picture. If you have a microbolometer-based TI, you will find this tip helps tremendously. Even BST-based imagers without a manual iris control will benefit. The key is to generate temperature differences which adjust the sensitivity settings of the software inside the TI.
The value of a thermal imager in overhaul is threefold. First, the technology helps identify hotspots that firefighters might otherwise miss. This clearly reduces the likelihood of a rekindle and limits additional property loss. Second, by identifying specific areas of concern, firefighters can limit their overhaul efforts (and therefore firefighter-caused damage) 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.