Finding Hidden Fires

When my kids were younger, they played hide-and-seek in our house using a thermal imager (yes, my kids get to play with thermal imagers). At the time, my daughter was 9 years old and my son was 4 and the way this would play out was consistent and inevitable. My daughter would hide her eyes, count to 50 and then promptly, within 30 seconds or so, locate my son no matter where he hid in the house. My son would then hide his eyes, count to 50 and then spend the next 30 minutes trying to find my daughter. In fact, I would often find myself thinking that my son would locate her faster if he didn't try to use the thermal imager. Of course, my daughter took great pleasure in tormenting him over his inadequacies. This sequence of events would normally only play out once or twice before my son would get frustrated and stop playing. What was my daughter doing differently to make her so successful?

Normally, when someone calls 911 and requests the fire department, the nature and location of the emergency is obvious. Family members lead us directly to ill patients and auto accidents are easily located by looking for the mangled vehicles stopped at odd angles in an intersection. Structure fires are typically located by the trail of smoke and the orange glow of the fire.

There are occasions, however, when the fire is hidden from view. We've all been there. It's 2 o'clock in the morning. There may be a hint of smoke; there may not. You smell it. That undeniable smell of something burning, but there is no obvious evidence of fire. It may be a residential structure of a large, commercial building. In these circumstances, a thermal imager may be the difference between a successful stop and a defensive operation.

A Wisconsin fire department was sent to the local high school to investigate a smoke odor. On arrival, firefighters learned that repair crews had been performing welding operations in the hallway earlier that day. Although firefighters could smell the telltale odor, no smoke was visible anywhere. A scan of the area with the thermal imager quickly discovered a hot spot just above the site where welding had taken place. Removing the drop ceiling revealed a small fire, which was quickly extinguished with just two water cans.

Saving Time and Money

Proper use of the TI saved the firefighters a great deal of time and avoided significant damage to the building. Had the hidden fire grown undetected, the department likely would have responded in the middle of the night to a full-alarm structure fire. The ceiling in the hallway area required replacement, at a cost just over $8,500. The value of the building alone was in excess of $29 million.

A New Jersey fire department used a TI to not only find a hidden fire, but to identify which house was on fire. A midnight dispatch to investigate a smoke odor outside brought firefighters to the neighborhood, but the absence of smoke and obvious fire left firefighters at a loss. One firefighter noticed a slight haze about one block from the original caller. The captain scanned several houses with the TI. Two houses appeared gray on the TI, but a third had a hot roof and attic that showed as bright white. Further investigation led firefighters to locate an attic fire in this home. The owners were away at the time, and the fire could have gone undiscovered until it was burning through the roof. Instead, firefighters had the fire extinguished within 20 minutes and kept the electrical fire from damaging any major structural members. Proper TI use prevented an extended incident as well as significant property loss.

An Ohio fire department received a call to a 6,500-square-foot residence for the smell of smoke. Once on scene, the firefighter also detected the smell, but given the absence of smoke and the size of the house, they decided to deploy several crews with thermal imagers to survey walls and ceilings. One of the fire crews quickly located a hot spot on the ceiling of the lower floor. This hot spot was well defined along its length (contained by the floor joists from the floor above) and diffused along its ends (uncontained). Firefighters brought in a large salvage tarp and a handline. They then pulled the ceiling in the area of the heat signature, exposing what had been a smoldering fire near an electrical box. The fire was quickly extinguished and damage was contained to four-by-four-foot area. A $2 million home with $3,000 worth of damage.

Proper Use

Each of the success stories above demonstrates how proper use of a TI can lead to saving time and preserving property. Proper use is the key, however. Remember that the TI does not "see through" most materials. It shows that the hidden fire has warmed the surface material in comparison to the rest of the building. In order to properly use your thermal imager in these types of size ups, you must:

  • Use the thermal imager to compare areas or buildings, noting odd areas of heat accumulation
  • Use these comparisons to formulate a logical explanation for what is being displayed on the TI
  • Gain an understanding of building construction and materials and how they may retain or hide heat
  • Understand how environmental issues, including the sun, boiler rooms and other high-heat sources, can affect the thermal signature of a building and its components
  • Verify, when at all possible, suspected problem areas with traditional investigative means (small inspection holes, feeling with a hand for heat, etc.)
  • Not use the thermal image as the sole basis for believing that a heat source indicates a hidden fire


Hidden fires pose numerous challenges and dangers. Finding these smoldering dangers frequently involves numerous inspection holes or merely waiting for the fire to break into the open. By properly using thermal imagers, firefighters can locate these fires faster, saving themselves tremendous amounts of time and energy. Prompt identification of a hidden fire also can result in significant property savings, as the fire is extinguished with less water and with less damage by fire, smoke and firefighters.

Back to hide-and-seek. What was my daughter doing differently? She had discovered that she could locate the footprints that my son left behind when he went to hide so no matter where he was or how long she counted, all my daughter had to do was turn around and follow the footprints. Eventually, my son caught onto this little trick and the game of hide-and-seek was no longer fun for either of them and they stopped playing altogether.

BRAD HARVEY is the Thermal Imaging Product Manager at Bullard. He is a veteran of public safety as a firefighter, police officer and paramedic and is certified through the Law Enforcement Thermographers' Association (LETA) as a thermal imaging instructor. Harvey has worked as a high-angle rescue instructor and is a certified rescue technician and fire instructor. If you have questions about thermal imaging, you may e-mail him at