Third, remember that "white" on your TI display does not always mean a fire. There may be activities inside the building that cause an odd heat signature on the TI. For example, a Type V residence with a sauna in the master bathroom might display a white area on the exterior walls, corresponding with the location of the sauna. In the Type IV mill, the boiler room against an exterior wall may also cause a different thermal signature for that portion of the building, compared to the rest of the wall.
A number of fire departments respond to more MVAs than they do structure fires. While a TI will not help treat a patient, the proactive fire department may use the technology to help in several ways during scene size-up. First, as you approach the scene, the TI may help you identify any liquid leaks. While it cannot differentiate brake fluid from gasoline, a thermal imager can at least notify you early that you have a potentially hazardous situation. Because the spilled liquid will usually have a different temperature than the ground, it should be visible to your imager.
Second, the imager may help identify skid marks to determine if there are other vehicles involved. For example, at an accident in a rural wooded area, the imager may detect the heat from skid marks going off into the woods or toward a ravine. During size up, this information can prompt firefighters to search for another vehicle off the roadway.
Third, at high-energy collisions, the imager may help identify victims who have been thrown from the vehicle. Because any person ejected from the vehicle should have a different temperature than the surrounding terrain, he or she should be visible on the imager. Because this type of scenario is most likely at night, the victims will normally show as white on the display. Keep in mind, however, that brush may obscure part of the victim's heat signature or block it completely. In winter storm conditions, it might also be possible for a victim to be covered with snow. Snow, being merely frozen water, will block the person's heat signature as well. The thickness of the snow layer, combined with the person's attire, will determine how much of the individual's heat is seen by your imager.
If a fire company is dispatched to investigate a possible hazmat incident, firefighters can use a thermal imager to help assess the risks. The imager can help identify the amount of product in certain containers, as well as identify the presence, location and movement of a leak.
Thermal imagers will show product levels in sealed containers if four specific conditions are in place concurrently. First, the product must be a liquid or a solid. Second, there must be a vapor space. Third, the vapor space in the container must be a different temperature than the product. Fourth, this temperature difference must be translated to the surface of the container. If all four conditions are in place, the imager should detect a product level line. While the likelihood that these four conditions will exist at a hazmat scene is good, it is not guaranteed. As firefighters train with and use the imager, they should be careful not to fool themselves into seeing product levels where none are actually visible.
Photo Courtesy of Bullard
This image shows how an imager can identify product levels under the proper conditions. The container on the right may be completely full, completely empty, temperature equalized or too insulated.
The thermal imager can also show the presence and movement of a leak. As long as the material stays on top of nearby surfaces, and it has a different temperature, it will be visible. This will be true as well for liquids that float on water, such as gasoline or fuel oil. Products that mix with the surface, such as alcohol mixing with water, will "disappear" from the imager. Materials that soak into the surface may be visible only if they change the temperature of the surface.
Note that the imager will generally not "see" leaking gases. However, since gases are endothermic when they escape from a pressurized system, the point of a gas leak may be seen as a cold spot on the container or piping. Also, remember that no thermal imager is intrinsically safe. If you or the hazmat team are concerned about LELs and UELs, do not bring an imager into the "hot zone."