How to Use the Features of Your Thermal Imager

May 1, 2005

Thermal imaging has advanced significantly in the past eight years. Durability, reliability, image quality and battery life have all improved. As firefighters have become more comfortable with thermal imaging, manufacturers have supplied more features to differentiate their products and help firefighters use the tool more frequently with greater success.

Three common features (available from several manufacturers) must be better understood by firefighters if they are to be used properly. These features are colorization, digital zoom and picture capture. Each of these offers specific benefits at emergency incidents.


Several colorization systems are available. One system that has phased out of the fire service created images using color instead of black and white. This feature generally did not offer any specific advantages during emergency incidents. Most current systems use a solid color (normally solid red) to indicate objects that are extremely hot. The exact temperature indicated varies according to the dynamic range (or maximum temperature) of the detector, although for most manufacturers, the temperature is over 1,000 degrees Fahrenheit (538 degrees Celsius). This color can identify the seat of an intense fire, helping firefighters properly place and aim hose streams.

The latest systems also use color shades to help firefighters identify varying temperatures, such as yellow/orange/red or orange/red. These shades appear in addition to the standard white-gray-black image to which firefighters have grown accustomed. Each manufacturer has a slightly different system, so practice with the system at your fire department. However, the use of this feature is universal. Generally, the colorization does not activate unless temperatures are extreme (over 500F/260C), so they have little advantage during overhaul (two exceptions are discussed below). This shading feature can, however, be very helpful in identifying dangerous thermal layers or heat currents. While the thermal imager (TI) normally only sees surface temperatures, superheated gases have special properties that make them visible on a TI. The shading systems can colorize thermal layers in shades of yellow, orange and/or red. This enables less experienced users to identify the thermal layer more rapidly, and make better decisions about how far to advance or how quickly to ventilate a structure.

Keep in mind that the temperatures indicated by colorization are estimations, just like temperature measurement on a thermal imager provides estimations. A number of factors, most importantly the type of material, affect the accuracy of the estimation. In general though, if you can “see” a gas layer on your TI, even if it is white and not colorized, treat it as a superheated thermal layer and act appropriately.

Two colorization systems are useful during overhaul. In a post-knockdown fire room, TIs can have difficulty selecting the proper sensitivity level for the heated room. As a result, they frequently display the room with an over-abundance of white, or as many areas of gray. Firefighters cannot easily pinpoint hot spots. These two low-temperature colorization systems specifically activate colorization at a lower temperature (one system functions automatically under 300F/149C, the other is user-activated under 500F/260C). These systems will paint hot spots a special color to help firefighters discern them more easily.

Digital Zoom

To ensure reasonable durability and reliability, fire service TIs have fixed optical systems. This makes the products easier to use, but makes optical zoom impossible. Some TI models incorporate digital zoom to give firefighters a closer view of a scene without forcing them to actually crawl closer. The digital zoom feature of a TI works quite similarly to digital zoom on a camera or video recorder, taking only a portion of the sensor and displaying it on the entire viewing screen. The most common zoom is 2X zoom, which uses the center portion of the detector to create the entire display.

The major advantage of this feature is that it allows firefighters to examine a scene more closely without exposing themselves to greater danger. It can be helpful in hazmat situations, overhaul, search and rescue or even when firefighters are looking for hidden fire. The disadvantage of digital zoom is that the enlarged image becomes blocky, or pixilated, which can make it more difficult to interpret.

Picture Capture

Essentially, picture capture incorporates a digital camera into a thermal imager, allowing firefighters to capture and store images from incidents. After the incident, the images can then be downloaded to a computer and saved for future use. Different manufacturers use different image formats and download processes.

The picture capture feature can be extremely helpful for training purposes, as it gives firefighters the capability to easily save and review actual images from real emergencies. This allows them to share educational tips with the rest of the department, or to help teach image interpretation skills to newer members. Fire officers can use the images to help with report writing, fire investigation and incident documentation.


Fire service thermal imagers have developed significantly from the simple white-gray-black systems of the past. As firefighters have demanded more options and features, manufacturers have addressed these demands. Colorization, when properly used and understood, can enhance firefighter safety by helping you understand the fire environment better. Digital zoom can help firefighters examine questionable scenes from a greater distance, while picture capture capabilities give firefighters greater training and record-keeping capabilities.

As always, be sure to practice with any features on your TI and train all members on proper safety procedures and image interpretation.

Jonathan Bastian is the former thermal imaging training manager at Bullard. He is certified as a thermal imaging instructor by the Law Enforcement Thermographers’ Association (LETA), the international public safety organization specializing in thermal imager certification and training. He is also a member of the NFPA Technical Committee on Fire Service Training. Educated at Brown University and licensed as a high school teacher in Illinois, Bastian served 12 years on the North Park, IL, Fire Department, including the last three as a captain. As health and safety officer, he led the development and implementation of the department’s rapid intervention team SOG. Bastian is a certified Fire Instructor I and Firefighter III, and he spent 12 years as an EMT-I/D. He has taught classes on thermal imaging, rapid intervention teams, and search and rescue operations. Bullard is happy to answer any questions about thermal imaging; contact the company at [email protected].

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