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Before committing yourself beneath a truss roof, use the thermal imager to look at those trusses. Are they deformed? Are they glowing white? What types of heat patterns do you see? Any indication of problems with the trusses should cause a re-think of the strategy. If you continue interior operations, then you must re-check these trusses constantly. Check new trusses encountered as you move and re-check for changing conditions. Numerous firefighters have been saved because of early recognition of truss failure using thermal imagers.
A thermal imager is not adequate, by itself, for determining integrity of the floor. You should examine the floor for unusual heat patterns; however, keep in mind that the thermal imager cannot see through anything. It only sees a surface, so it can tell you that the floor is present, but it cannot tell you that the floor will support you.
When navigating, you can use water from the hose to create thermal contrast as well as to mark areas of the building. If you come across a secondary means of egress while searching, use the handline to wet the item. This will create a temperature difference that is easy to identify from a distance. If you had to make a hasty exit, you can use the thermal imager to look for the large, dark area on a wall rather than to differentiate one window from another.
Should you find yourself needing to be rescued from inside the structure and you can find your way to an exterior wall, strip wall coverings until you arrive at the corrugated metal. Place the handline directly against the metal as high as you can get it and crack the nozzle, causing water to run down the metal. Metal is highly conductive and the thermal difference is many times visible from the outside. Crews on the outside can then use a thermal imager to look for the dark spot on the wall. Several quick cuts with a rotary saw may be all that is necessary for successful extrication.
Vertical, horizontal or both, the thermal imager can indicate areas of heat accumulation from outside the building. From above the building, the thermal imager can tell you the hottest areas of the roof. Often, these are items that penetrate the roof such as vents, skylights, plumbing and heating, ventilation and air conditioning (HVAC) systems; however, some of these can be used as natural vent points. Again, as we discussed regarding floors, you cannot use the thermal imager to assess the structural integrity of the roof.
The effects of ventilation can also be assessed with a thermal imager. If you denote areas of heat accumulation, employ ventilation tactics and those areas of heat accumulation diminish, odds are the ventilation was effective.
These types of uses must be practiced. Pre-plans, fire inspections or company-level drills all create opportunities to try them. Lightweight construction presents unusual hazards to firefighters. Your thermal imager can be immensely valuable, if you use it correctly and consistently.