Thermal Imaging: Don't Forget Your TI During Overhaul

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...


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The most important tip to remember during overhaul is that the TI displays scenes on a relative basis. This means that an object that is “hot” on the display (normally shown as white) is hot in comparison to the other items in the scene. This can make image interpretation confusing during overhaul, especially after knockdown and when looking for hotspots. To make your TI more effective in overhaul, consider the following:

• Thermal imagers show temperature differences. After knockdown, if the scene appears bland on the display, spray some water to create temperature differences. This gives the TI other reference temperatures and, as a result, enables it to generate more useful images.

• A “hot spot” does not always mean “open up.” Thermal imagers are very sensitive. An area may be relatively hot, but not absolutely hot. That means it could show as white on the display, even though the area is not a hot spot that deserves further examination by firefighters.

• Always use traditional techniques to determine whether a hot spot really needs to be opened up. A TI is merely an “assist” to overhaul and cannot replace traditional techniques. Feel the area for heat by using your hand. Or, use the TI and compare it to something with a known temperature. The easiest comparison point is often a partner’s hand. If you see an area that appears white on the TI, place an ungloved hand in the same picture as the object. If the hand appears gray and the object stays white, the object is hotter than the hand. If the spot in question is roughly the same color as the hand, then it is probably not a hot spot that needs attention during overhaul.

Understand what you see

If you are not comfortable with the indicators and tools on your TI, you will be frustrated when overhauling. 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. 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 creates significant temperature differences and helps the thermal imager generate a better picture.

As with all thermal imager applications, the ability to use a TI effectively in overhaul requires practice. You cannot expect to use it two or three times per month and become proficient at analyzing overhaul scenes. Be sure you are using your TI as frequently as possible to understand how the subtleties of the images can change your course of action. Also, do not forget the traditional overhaul investigative techniques that can help you confirm your image interpretations. n