IFSJ Exclusive: The true colour of fire with Insight Training LLC

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

Thermal Imaging Cameras offer a variety of application-based colour palettes for the end user to choose from. Certain manufacturers offer as many as 23 different choices of colour palettes. In addition to the variety of colour 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 colour palettes incorrectly. How can these colour palettes be used incorrectly?

To properly address this issue, we must first define these various application-based colour palettes and their appropriate and intended environment for use. Each specific colour 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 colour palettes have uses that were not originally intended for firefighting – they were intended for low temperature and low contrast environments except fire-based colour palettes such as TI Basic. This is especially important to note as the fireground will have much higher temperatures than most of these colour 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 maximise the effectiveness of their investment.

Establishing common ground

Firefighters are quick to recognise the colour palette known as TI Basic. NFPA 1801, The Standard on Thermal Imagers for the Fire Service-chapter states regarding colourisation the following:

In the TI Basic mode, the heat colour reference bar shall have a colour scale that includes only the following colourisation: Greyscale — at the bottom of the heat colour reference bar before colour indication begins and shall not be more than 50 percent of the overall height of the heat colour reference bar; yellow at the low end of the heat colour reference bar; orange in the middle of the heat colour reference bar; and red at the high end of the heat colour reference bar.

This colour palette is simple and intuitive for all users to understand except for the following variable: Manufacturers choose when these colours engage, and they are approved by NFPA if they follow the approved colour/temperature progression with no more than 50% of the colour palette being in grey scale.

This creates a problem for firefighters as they can pick up any of the currently certified NFPA 1801 Certified Thermal Imaging Cameras and each will show colourisation at different temperatures at differing pixel percentages and some show colourisation in high and low sensitivity modes.

The issue of non-uniformity in colour temperature correlation continues to worsen when we notice that many manufacturers offer an overwhelming selection of non-firefighting application-based colour palettes such as: Rainbow or High Colour, Iron Bow, Fire & Ice, Black Hot, Green Hot and many more.

One of the best explanations for how and why colour palettes are developed comes from Teledyne FLIR: “In thermal imaging, each individual pixel represents a specific temperature data point. These data points are assigned a unique colour or shade based on their value, meaning that as the thermal sensor detects changes in heat energy, it will express this change by adjusting the colour or shade of a pixel. These pre-set gradients—or thermal palettes—determine pixel appearance and help identify different heat sources throughout a scene.”

By assigning specific temperature data points to a specific colour or shade this allows firefighters to quickly identify areas of interest. But which colour palettes should and should not be used in the realm of firefighting?  Per NFPA 1801, TI Basic is the recommended colour palette for firefighting but there are numerous other colour palettes available for use. The issue is not the colour palettes themselves but the end user and their level of overall knowledge.

Colour palette options

First, the end user must be trained on the specific application-based colour palette. While the temperature and conditions of a scene is the same, each colour palette will detect and interpret the scene differently. By understanding the colour palette and its intended use, a firefighter can use these colour palettes to their advantage in various emergency situations.

According to Dave Lee from FLIR Delta: “Not all colour palettes are well suited for every situation. In fact, some colour palettes can even make your job harder or even hide what you are looking for.”

Iron-Bow: The Iron-bow colour palette is one of the most popular palettes chosen by thermography professionals. It is used extensively in the inspection industry when viewing roofs, solar panels, and electrical equipment. It is also used in pinpointing skin temperature variations in industrial thermal imaging cameras known as EBT or elevated body temperature devices. Many TIC manufacturers do not publish the temperature colour correlations for this palette.

Rainbow Colour Palette: In thermography, the rainbow colour palette is typically used for demonstration purposes to show clients/customers areas of potential interest as the broad spectrum of colours provide a separation of specific areas of interest. It is also used in the electrical industry when inspecting circuit boards and electronic components. In emergency services, this colour palette can lead to confusion for firefighters due to the manufacturer does not publish the colour/temperature correlations.

White Hot: Prior to the addition of TI Basic Plus, the standard colour palette was White Hot. With this, the hottest object within the field of view of the will appear white whereas the coldest object within the field of view will be colorised black. The issue arises when we are trying to determine the areas that are in-between black and white.

Firefighters who use this colour palette would be wise to consider any area that is white (in fire conditions) as hot and cool the area until it becomes black. Shades of grey are not as easy to differentiate as thermographers tell us. When compared to the other options the firefighter must choose from within the various colour palettes; White Hot is the simplest option for staying oriented.

Colour selection criteria guide

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

The following colour selection criteria guide is designed for applications where time is not of the essence The end user should consider the following questions:

• What am I looking for? High Heat? Low Heat? No Heat?

• What is the background temperature compared to the object of interest?

• What type of Incident? Fire, Lost Person, Haz-Mat, Active Shooter?

• Do I need detail, or Do I need simply to identify the area of interest?

• Who is the operator? Are they colour blind or have issues with their eyesight?

This three-point model can simplify the process.

1) Check Conditions: What are the overall background temperatures compared to the object of interest? Toggle through the available colour 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.

2) Colourisation Adjustment: Certain colour palettes have adjustable temperature/heat spans to highlight areas of interest.

3) Contrast Check: Certain Colour Palettes offer too little contrast for contexts where clarity and detail are of the utmost importance.

In summary, 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 January edition of IFSJ. To read your FREE digital copy, click here.

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