Improving Firefighter Safety & Enhancing Mission Success: Thermal Imaging Camera Technicalities

Over the past 30 or so years infra-red technology and thermal imaging cameras (TIC) have played a key part both as an aid to fighting fires and also enhancing firefighter safety. Over that period both the technology and the application of the technology has significantly moved forward.

Recent events, such as Shirley Towers (UK) in 2012, Tianjin Port (China, 2015), Fort McMurrary wildfire (Canada, 2016), Pedrógão Grande wildfire (Portugal, 2017) and Grenfell Tower (UK, 2017), have continued to drive forward the importance of specialist firefighting equipment and highlighted the need to equip firefighters to operate in the most extreme and demanding of environments, over a sustained period. Each of these events has its own sad tale of tragedy and loss, which makes it all the more important that lessons are learned, understood and applied. The onus to learn the operational lessons, clearly resides with the firefighting community however, the need to evolve the technology, meet the standards and enhance firefighter safety lies with the equipment manufacturers.

Specifically looking at TICs, we will explore the importance of operational display quality and sensitivity, the understanding and implication of colorization and the use of additional features to improve firefighter safety, enhance mission success and reduce time on task. To do this, let us firstly assume that TICs are manufactured to an appropriate standard, which includes the use of water, heat and chemical resistant materials, includes safe battery technology, industrial grade high temperature components, an acceptable level of IP rating, and are both CE & NFPA certified; these may sound like basic requirements however, not all cameras are the same and not all manufacturers adhere to these most basic needs. The above said and assumed, we can now move on to discuss and review the important interface between firefighter and TIC.

DISPLAY QUALITY

All modern TICs use digital signal processing (DSP) to help achieve the clearest displayed image but like all digital cameras, optical or infra-red, DSP processing adds artefacts to the image and can potentially reduce clarity or add distorted elements.

Contouring, similar to that found on an ordnance survey map to describe height, is one of these such elements that can appear on a camera where the processing algorithms are not optimized for the fire scene and therefore add distortion to an image. Likewise fixed pattern noise (which is often viewed as a net curtain effect), random noise speckles, and over contrast (edge enhancement) can all be introduced by DSP algorithms. These pertain to give the operator a better image, but actually add in more problems than they solve; either cropping the image, removing scene data or deleting background information. The purest and cleanest image, and therefore the most operationally appropriate image, usually originates from using a 1 to 1 sensor/display pixel ratio, which will reduce the amount of necessary DSP and associate image clutter or noise.

In addition to DSP, screen brightness and its application in a fire environment is critical. Modern consumer LCD screens are designed to work against the ambient light and provide vivid displays, even in brightly lit environments, these are optimized for the office or home environment. When used in a harsher operational environment, such as a shout, the firefighter is likely to encounter hostile conditions that may be smoke filled, poorly lit, dirty and high stress. Therefore, consideration should be given to the display, is it too bright and will it provide unwanted illumination across the mask visor, causing temporary “night blindness” and introducing eye strain or ‘vision fatigue’?

Finally the most important factor in image quality and something that is all too often overlooked is the background detail. Having a clear image of the hottest part of the scene i.e. the fire is incredibly important and the majority of TICs on the market do this well. However, a firefighter is potentially more interested in the environment surrounding the fire or wider scene, which may include casualties, entry and exit points, trip and snag hazards etc.

Most TICs are more than capable of producing a good image of the fire but sacrifice the background detail, denying the firefighter the ability to see ‘past the fire’, dissolving the background in to the flames. This severely limits the capability of the TIC but more importantly places the firefighter at risk and increasing their time on scene.

UNDERSTANDING COLORIZATION

TICs use temperature sensitivity to inform the display and provide colorization. Inaccurate readings are likely to be magnified and result in inaccurate colorization. This in turn introduces false information into the decision making cycle of the firefighter and incident commander; scene assessment, method of attack, ingress – egress points, time on scene, workload, heat index etc.

While it is accepted that a temperature accuracy of around 10% is sufficient, it is important that this accuracy is available for the whole operational temperature range of the camera. Any larger variation may cause a large enough temperature error to be the difference between the ignition point for stored pressure vessels and accelerants or accurately observing ceiling gas temperatures close to flashover. In addition to temperature sensitivity, understanding the dynamic range of the camera can ensure that it won’t red out at critical times; the upper dynamic range is effectively the maximum temperature the camera can see up to, above this the TIC becomes overwhelmed and may “red out”.

Therefore, a minimum acceptable upper limit should be 650°C (1202°F) based on flashover and temperature sensitivity however, it is worth noting that even during compartment training, the temperatures can reach in excess of 700°C to 800°C (1292°F to 1472°F), rendering a lower dynamic range camera useless. Having understood temperature sensitivity and dynamic range, we can begin to introduce colorization to the display; this can be a source of confusion, especially if the TIC is not set to standard NFPA temperature bands.

Traditional non-firefighting TICs, often used for surveillance or search operations, use colorization software to apply color to the hottest and the coldest areas of the observed scene, spreading the colors accordingly across the observed scene. As the operator scans the scene, the colors continually adjust, resulting in a potentially confusing image and inaccurate information, how do you determine what is hot and hottest?

Therefore when choosing a TIC and in particular the standard start up mode (NFPA) for a fire attack, it is essential that a particular temperature is consistently associated with a color; for example red maybe 900°C (1652°F) or hotter, orange could be 800°C (1292°F) plus and yellow 500°C (932°F).

It should be noted that other modes maybe available and selected to enhance firefighter safety, increase operational effectiveness and reduce time on scene. For example, when damping down a wildfire or conducting overhaul, a lower dynamic range for that particular scene or operation mode may be applicable. The correct mode of operation will allow the operator to highlight hot spots, identify future ignition points and the seat of smaller or smoldering fires but to use these effectively, standard operating procedures and training must be implemented and continually refreshed.

CONCLUSION

The majority of well-known TICs manufacturers have large screens, temperature measurement and easy to read displays, but when it comes to providing the user with a TIC that absolutely performs in the most demanding fire environments, there can be absolutely no compromise on quality or testing; the ability to drill down into what the firefighter really requires is key to making the right choice of TIC.

Ultimately, fundamental principles of all TICs remain the same and when tested in a benign environment, many of the more traditional search and surveillance cameras can offer enhanced image quality over a specialist fire TIC. This does not make them appropriate for firefighting and the question remains, if it isn’t tested and certified for that environment, would you trust your life or those under your command with it?

To summarize, below is a list of 10 quick questions to consider when reviewing fire TICs and operational requirements:

1. How bright is the screen? Try testing the TIC in a dark room or, if available, a smoke house.
2. What image data am I losing through image processing and “enhancement” features?
3. What’s the ratio between sensor and display? Is data being unwittingly cropped from the image.
4. Can I see the whole scene and beyond the fire? Try testing this with a heat source such as a tealight.
5. What is the dynamic range of the camera? How will the camera be used and up to what temperature?
6. How accurate is the temperature indication? Are you happy with the spot temperature reading? Are you happy with the color representation?
7. What SOPs and training do I have in place to increase the functionality of a TIC?
8. How long does the camera take to perform a NUC (non-uniformity correction) or change sensitivity/temperature range?
9. Does the camera use suitable materials? Can I can decontaminate the camera? What’s the IP rating?
10. Is the camera CE and NFPA certified?

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