Investigating the Unknown Using Thermal Cameras

Jun 14, 2022

The United States military initially declassified thermal imager technology; the mindset was that a THERMAL IMAGER was used just for firefighting.

As time has gone by, through training, education, and widespread adoption, the fire service has come to realize that there is a THERMAL IMAGER application on every response—simply take the blinders off and think outside the box.

Not all calls a fire department responds to are actual fires or have working fire conditions, but there are many calls where a THERMAL IMAGER should be used. These applications include size-up, overhaul, search and rescue, hazmat, industrial, and smells and bells—all calls that require investigating the unknown. The unknown is anything that can’t be seen by the naked eye, such as heat signatures from passive emitters (inanimate objects), active emitters (living organisms), and direct emitters (energy sources).

Investigation of the unknown comes with great responsibility to keep the public and homeowners safe. They look to the fire department as experts, and to make a mistake or miscalculation is not an option. A THERMAL IMAGER, in this case, is that valuable tool that you can’t afford to leave in your apparatus. It is often a difference-maker in uncovering that lingering or hidden heat source.

Uncovering the Unknowns in Smells and Bells Calls

The most common smells and bells calls are electrical issues, such as an overheated light ballast; electrical panel breakers; an improperly wired receptacle; or, in an industrial facility, overheated motors, bearings, or conveyors. Other applications besides smells and bells calls at which a THERMAL IMAGER can unveil unknown information include liquid levels in containers at a warehouse or propane tank levels at a bulk station during hazmat responses. In all cases, a THERMAL IMAGER is your most valuable tool for investigating and uncovering these unknowns.

Picture 1 Unknown heat signatures discovered behind a wall ▲

Picture 2 A wall heater behind the wall ▲

Picture3 A ceiling fan not working vs. a ceiling fan working properly ▲

At a recent THERMAL IMAGER training session, we compared the heat signature of two ceiling fans (Picture 3), one nonoperational and one operational. It was discovered that the nonoperational ceiling fan had an overheated motor. This particular call didn’t require us to cut a hole in the wall to investigate further because the ceiling fans are exposed. Our THERMAL IMAGER clearly showed that the fan’s motor was too hot to be nonoperational. However, identifying hidden heat sources, like those behind a wall in picture 1, can be more challenging.

Understanding the Noise Sensitivity Temperature Difference (NETD) of a THERMAL IMAGER can help firefighters interpret hidden heat sources. The NETD allows the THERMAL IMAGER to distinguish between very small differences in thermal radiation within the image. This is sometimes referred to as “thermal contrast.” NETD is typically expressed in milli-Kelvin (mK), and today’s fire service TIs range anywhere from 30mK to 100mK, making some of these devices highly sensitive for investigating unknown heat signatures or sources. TIs with lower NETD generally have better image quality and allow a firefighter to better interpret the details of an image. This additional detail can sometimes prevent a firefighter from having to open a wall because it’s easier to distinguish between, for example, a hot water pipe or another unknown heat source hidden behind a wall.

Those unknown heat signatures behind the wall in photo 1 were investigated during another THERMAL IMAGER training session. It was concluded that there was a heater on the opposite side of the wall (picture 2) and piping from the boiler water heating system inside the wall—mystery solved!

This was a good training exercise for the fire department members, who were applying their newly taught THERMAL IMAGER skills in a real application. Practice starts with you as a firefighter or officer who is assigned the use of a THERMAL IMAGER. As with anything, practice makes perfect. The more often you use and experiment with a THERMAL IMAGER, the more proficient you will become in its operation and interpreting of images.

Whatever or wherever the response takes you, be sure to take your THERMAL IMAGER with you, as it is a valuable tool to aid in investigating the unknown.


This article by Manfred Kihn was published in Fire Apparatus Magazine in the December issue of 2021.