The critical role of thermal imaging color palettes

April 15, 2024

Andy Starnes, Instructor at Insight Training LLC, explains why with thermal imaging camera color palettes, what you see is not always what you get

Thermal Imaging Cameras offer a variety of application-based color palettes for the end user to choose from.

Certain manufacturers offer as many as 23 different choices of color palettes.

In addition to the variety of color palettes available, certain manufacturers offer feature specific benefits such as hot spot/cold spot tracker, electronic thermal throttle and more.

With such a variety of choices, options, and applications; it is no wonder firefighters are often seen using these application-based color palettes incorrectly.

How can these color palettes be used incorrectly?

To properly address this issue, we must first define these various application-based color palettes and their appropriate and intended environment for use.

Each specific color palette is assigned what is known as false colours by the programming in the thermal imaging camera based on different intensities of radiation at different levels.

Most of these color palettes have uses that were not originally intended for firefighting – they were intended for low temperature and low contrast environments except fire-based color palettes such as TI Basic.

This is especially important to note as the fireground will have much higher temperatures than most of these color palettes listed here were intended for.

Fire departments who are choosing thermal imaging cameras would be wise to do their research before purchasing any device that offers many options that may not be applicable to their service delivery model.

In other words, if a department chooses a highly complicated device with numerous application specific options, they must invest in thermography-based training for their firefighters to maximize the effectiveness of their investment.

Establishing common ground

Firefighters recognize the TI Basic color palette as per NFPA 1801’s standard, which mandates a specific colorization for thermal imagers: greyscale at the bottom of the heat color reference bar (not exceeding 50% of its height), yellow at the low end, orange in the middle, and red at the high end.

However, inconsistency arises as manufacturers determine the activation temperatures for these colors, approved by NFPA based on the progression of colors within the set limits.

This results in variances in temperature display across different NFPA 1801 Certified Thermal Imaging Cameras, complicating usage for firefighters.

The issue is compounded by the plethora of available non-firefighting color palettes, such as Rainbow, Iron Bow, and others, which can overwhelm users.

Thermal palettes are designed to represent temperature data points with specific colors or shades, aiding in the identification of heat sources.

Despite the recommendation of TI Basic for firefighting by NFPA 1801, the challenge lies in the user’s understanding and selection of appropriate color palettes for effective application in firefighting scenarios.

Colour palette options

The end user must be trained on the specific application-based color palette.

While the temperature and conditions of a scene is the same, each color palette will detect and interpret the scene differently.

By understanding the color palette and its intended use, a firefighter can use these color palettes to their advantage in various emergency situations.

Not all color palettes are well suited for every situation.

In fact, some color palettes can even make your job harder or even hide what you are looking for.

The Iron-Bow palette, favored by thermography professionals for inspecting roofs, solar panels, and electrical equipment, and for detecting skin temperature variations, often lacks published color/temperature correlations by manufacturers.

The Rainbow palette, used for demonstrations and in the electrical industry, can confuse emergency services due to its inconsistent color temperature correlations across manufacturers.

White Hot, superseded by TI Basic Plus, simplifies visualization by displaying the hottest areas in white and the coldest in black, though it challenges firefighters with its less distinguishable shades of grey.

Effective color palettes should be specific, informative, and not overwhelm the user, accompanied by usage instructions.

Colour selection criteria guide

In situations such as the fire ground, a firefighter does not have the luxury of time to select from various color palettes.

We recommend the following guidelines.

The end user must ask themselves the following questions: Do I have seconds? Such as a fire or rescue scene? -or- Do I have minutes? Such as a lost person search operation or drone application as pictured here.

When seconds count such as on the fire ground for fire attack or search, newer standard fire service TICs will turn on and default to TI Basic without selecting or pressing any additional buttons other than the power button.

If a firefighter is in another application mode other than TI-Basic, they can simply tap the green power button and it will return to TI-Basic.

When the end user has more time such as during investigations, size up, or overhaul situations, they can quickly select their color palette of choice.

The following color selection criteria guide is designed for applications where time is not of the essence.

Step one: check conditions.

What are the overall background temperatures compared to the object of interest? Toggle through the available color palettes while keeping in mind that as the environment changes so will the discernible details.

Is this a high heat or low heat situation? Be aware that as the overall temperature increases, the TIC will switch from high to low sensitivity which can cause a loss of detail.

If the end user is viewing a high heat scene, they would be wise to stay in an application mode that offers dual gain or high and low sensitivity.

If they are viewing a low temperature scene, a single gain application mode will benefit them greatly.

Step two: colorization adjustment: Certain color palettes have adjustable temperature/heat spans to highlight areas of interest.

Step three: contrast check.

Certain color palettes offer too little contrast for contexts where clarity and detail are of the utmost importance.

Thermal imaging cameras offer a variety of options and features but they cannot be used to their maximum potential without proper education and training.

We recommend learning and training on your specific model of thermal imaging camera.

Colour palettes and application features vary by manufacturer.

This diagnostic tool can be an asset or a detriment.

The determining factor of its overall effectiveness is ultimately up to the knowledge, skill, and understanding of the end user.

This article was originally published in the April 2024 issue of Fire & Safety Journal Americas. To read your FREE digital copy, click here.

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