The fire service has been using thermal-imaging cameras (TICs) successfully since the 1990s, and many lives have been saved through their tactical use. Since their first implementation TICs have improved greatly and their overall cost has reduced dramatically, making them more readily available to the fire service.
However, the education and training on TICs has not been updated, nor has it been the primary focus for the fire service. This is exemplified in many fire departments as they will have newer apparatus, newer SCBAs (BAs) and PPE but they will still be using 15–20-year-old antiquated TICs. The advances in thermal-imaging technology have been quite staggering, as shown by the adjacent photos by Max Fire Box which compare the image clarity of a 20-year-old TIC with that of a two-year-old TIC. This can be compared to viewing a black-and-white television versus a modern-day LED High Definition TV.
Traditionally, the view of the fire environment has been an optical one. Firefighters have been taught to read the building, read the smoke and judge the IDLH (Immediately Dangerous to Life or Health) environment based on what they see with the naked eye, and to rely on feeling the heat as a measurement of thermal severity. This tactical measurement leaves out an unseen critical perspective known as thermal data. Thermal radiation is one of the fundamental methods of heat transfer which firefighters cannot see. This lack of understanding, and in many cases a total absence of training, has created an education gap that leaves many firefighters literally in the dark with a device that they don’t know how to use properly but which could potentially save their lives, save their citizens’ lives and enhance their overall fire-ground effectiveness.
In this article we will address some of the misconceptions or ‘myths’ of fire service thermal-imaging use. The term ‘fire service thermal-imaging camera’ or TIC will be used as there are many different types of thermal-imaging cameras for use outside of the fire service which have various capabilities that firefighters currently do not use nor have training on. We will address these issues with factual, evidence-based data, and these references can be found at the end of the article for further reading and review.
Myth: ‘I don’t need a fire service thermal-imaging camera to tell me how hot it is; I will wait until my ears are burning or pencil the ceiling to measure the heat.’
Firefighters are taught many valuable concepts and skills as they progress through their career. Unfortunately, many of us (including me) were never taught to measure heat correctly. For example, NFPA 1971: The Standard on Protective Ensembles for Structural Firefighting and Proximity Firefighting requires that all firefighter PPE (coats, trousers, gloves and hoods) be tested to perform and certified to a certain value known as TPP or thermal protective performance (NFPA 1971 p.64). This data originated from Alice Stoll’s work, which is now known as the Stoll Curve. This data was used to measure all of the variables that were required to produce a second-degree burn on a human victim. This testing was done in the 1950s and ’60s on US sailors. Her work is now the basis for the thermal protective performance ratings in NFPA-certified firefighting garments or PPE (Oberon p.1). The minimum requirement is 35, which provides 17.5 seconds of thermal protection until the wearer receives a second-degree burn. At first this seems very ingenious, but we as firefighters have used this protection to our own demise; as the humanist Huxley stated so eloquently, ‘…it has become apparent that what triumphant science has done hitherto is to improve the means for achieving unimproved or actually deteriorated ends.’
Firefighters in today’s modern environment are so well encapsulated that by the time they feel painful heat sensations their PPE is saturated with heat energy. Once their PPE is saturated, the heat energy begins to transfer to the firefighter’s flesh. When a firefighter feels bee-sting-like sensations of pain that force them to withdraw or drive them to the floor this is known as ‘alarm time’. This is the amount of time between feeling pain and actually suffering a burn. When this occurs, firefighters are about to be burned as their skin is at or approaching 130°F (54°C). This is the temperature at which the Stoll Curve found that a second-degree burn occurs in a human victim. Stoll’s work also proved that if the skin temperature continues to rise, then at 140°F (or 60°C) the human body’s pain receptors are turned off! Also, in the FEMSA manual, which is included with every piece of firefighter PPE sold in the US and Canada, the following quote can be found: ‘If your protective ensemble comes in contact with a hot environment or a hot object, you may be burned beneath your protective ensemble with no warning or no damage to the protective ensemble. Be constantly alert to the possibility of exposure to a hot environment, hot objects or other hazards.’ (FEMSA p.2–4)
Therefore, to use the human body as a thermometer in today’s fire environment with modern advancements in PPE is to force firefighters into a defensive position meaning it may be too late for them to respond, withdraw, or cool the environment before they are burned or killed. It is imperative that firefighters understand thermal severity through the eyes of a Fire Service TIC to ‘see the heat’ and not wait until they ‘feel the heat’.
Myth: ‘Isn’t thermal imaging just point, shoot and read the temperature? Why do firefighters need in-depth training on this device?’
Another problem encountered when teaching firefighters how to properly use a fire service TIC is in the tendency to read the spot temperature, which is the temperature reading in the lower right-hand corner of the screen. First and foremost, firefighters need to understand that fire service thermal-imaging cameras are not thermometers. This numerical reading of the temperature is a small measurement of a 12in area calibrated to +/- 3°C if the TIC is within its proper distance to the target and without any atmospheric attenuation that may affect its measurement. This measurement is known as an ‘apparent temperature’ which is an approximate value that falls within certain variables. When the fire service TIC is calibrated it is done so by measuring the temperature on a target at a pre-set distance with no smoke, fire or moisture that would interfere with the measurement. And in the instruction manual of every fire service TIC, the following words can be found in regard to relying on the spot temperature: ‘Do not use temperature readings as exact measurements.’ On the fire ground and in a fire, there are many variables that can cause this measurement to be far from correct. These variables are many and are not limited to the following:
- Proper distance to the target: fire service TIC’s distance-to-spot ratio accuracy can vary from as low as 10:1 (10ft away measuring a 1ft square) to as high as 900:1 (900ft away measuring a 1ft square).
- Emissivity: one of the most important variables in temperature measurement, emissivity is an object’s ability to emit heat. Emissivity ratings are defined as fraction of energy (rated between zero and one) in comparison to a perfect black surface, which has an emissivity value of 1.
A TIC detects thermal radiance from solid surfaces and from gases that radiate in the 8–14-micron spectral range. Emissivity affects the radiation in a way that can make the surface or gas appear to be a temperature other than what it actually is. In general, surfaces that are black and rough in texture tend to have high emissivity, and surfaces that are shiny/smooth tend to have lower emissivity. This is exemplified in the adjacent photo of the Max Fire Box after a fire-behaviour demonstration burn. The sides of the box are made of diamond plating (a very shiny material with low emissivity) which causes the TIC to read the reflected apparent temperature, which is the ambient temperature around it and which is incorrect. Some other variables that will affect a Fire Service TIC’s measurement are listed below:
- Wind: winds as low as 3 miles per hour can cut temperature measurements by 50%.
- Moisture: long-wave infrared energy can be blocked or dissipated as it moves through steam. Environments with sprinkler heads flowing, or high moisture content, may limit or block the TIC’s ability to measure or see. The lens of the TIC may become obscured with moisture, preventing it from working properly.
- Optical density of the smoke: the thicker the smoke in a fire due to particulates, lack of ventilation and the type of material burning can absorb more energy between the target and the fire service TIC, which can limit the range and effectiveness of certain devices. In the NIST research paper it was found that heavier smoke conditions can reduce the contrast transfer function (CTF), which is the TIC’s ability to discern finite details between different temperatures of objects at a distance (NIST p.41).
Myth: ‘A thermal-imaging camera can read smoke or gas temperatures.’
There are many types of thermal-imaging camera available today. Some of them can read gas temperatures and are known as optical gas imaging cameras. However, fire service thermal-imaging cameras do not read gases, nor do they accurately read smoke temperatures. This is due to the following:
- Emissivity: fire service TIC’s measure heat from surfaces that fall in the emissivity range of 0.95 to 0.97. There are only three known gases that fall into this range –ethane, ethylene oxide and hydrogen cyanide.
- Different range of the infrared spectrum: fire service TIC’s see or detect long-wave infrared energy, which falls into the spectral range of 7–14 microns (a micron is a millionth of a metre). Many gases fall into the spectral range of UV light, Short Wave Infrared (SWIR) and Mid Wave Infrared (MWIR). A Fire Service TIC does not detect infrared energy within these ranges.
Firefighters are encouraged to view the environment knowing that what the TIC is showing them is heat signatures and convection currents coming from surfaces.
Myth: ‘All TIC’s are the same.’
To believe such a statement can ultimately cost the department by an improper purchase and can lead to firefighter injuries or deaths. In the NIST research paper the following statement was made in regard to image quality: ‘It should be emphasized that the TIC optical system, electronic processing, and display quality make large contributions to overall image quality.’ (NIST p.36) Each fire service TIC that is produced today uses a variety of detectors, different electronic processing, and some are even using interpolation, which is a form of image enhancement that allows the firefighter to see more detail than ever before.
In addition to this there are predominately two major types of fire service TIC’s available today: situational-awareness TICs & decision-making TICs. Both are necessary and useful in their proper context, but to use a situational-awareness TIC as a decision-making TIC will ultimately lead the end user to a very dangerous and disappointing conclusion. What is the difference between the two types of fire service TIC? A situational-awareness TIC can be simply described as a single-purpose unit designed to prevent firefighter disorientation. They are generally smaller in size (can be hand-held, facepiece mounted, or SCBA integrated); and they are generally lower resolution and have a slower refresh rate. A decision-making TIC can be described as one that meets the following criteria: high resolution (minimum of 320×240 pixels), fast refresh rate (at least 30Hz), 3.5in viewfinder or display screen, and a high dynamic range (from 0 to 1200°F/650°C).
What does this mean to the end user or firefighter? First, lower-resolution fire service TICs have very short ranges of visibility and measurement (generally 7–10ft/2–4m). Secondly, they typically have a lower distance-to-spot ratio which means they are only able to accurately measure or determine a heat source at a relatively close distance such as 10ft away, which limits the firefighter’s tactical decision-making abilities. Thirdly, they tend to have a slower refresh rate. Some are as low as 9Hz (1Hz is one frame per second). The human eye sees at 27Hz. Therefore, the NFPA 1801 minimum for refresh rate is 25Hz. This is why we do not recommend purchasing a TIC less than 25–27Hz. TICs that have a refresh rate less than this will trail or lag when scanning, which can cause the firefighter to miss large areas as the TIC will shutter to catch up. As the TIC shutters or NUCs (non-uniformity correction) it briefly ‘closes its eye’ by the process of an electronic shutter that fires in front of the lens allowing the pixels on the detector to be wiped clean and a new image to be formed as the pixels receive new infrared heat signatures. In a 9Hz fire service TIC, the time it takes to perform this operation can cause firefighters to miss valuable information. For example, some situational-awareness fire service TIC’s take 3–5 seconds when they encounter large heat signatures as the TIC switches from high sensitivity to low sensitivity.
In my tenure in the fire service, I have seldom encountered a patient firefighter in an environment where every second counts, nor do they have the luxury of time. This is why these lower refresh rates are not optimal nor practical for use as decision-making TICs. But why would an organisation or department try to use a situational-awareness TIC improperly? Because they don’t know what they don’t know and for budgetary reasons. A smooth salesperson who shows them that they can buy a TIC for every firefighter for $1,000 versus one high-resolution decision-making TIC at five times this amount or higher can sway the buyer quite easily. We have read articles across the US and Canada where departments have disposed of their hand-held fire service TICs and replaced them with lower-cost, low-resolution, situational-awareness TICs. They have even made public statements that their firefighters are now better prepared. This is an illusion of superiority created by a lack of education and unethical salesmanship. Situational-awareness TICs are extremely important to firefighters and if a fire department can afford to outfit every firefighter with one, they will find that their firefighters will be safer by preventing firefighter disorientation. However, they are not meant nor designed to replace a high-resolution, faster refresh rate, higher-dynamic-range decision-making TIC.
Myth: ‘Fire Service TICs show colourization when it is too hot!’
Studying numerous models of fire service TIC and working diligently to stay up to date and knowledgeable on new technologies as they emerge onto the market is a constant battle. Thus, many firefighters are not educated on the fact that colourization of the thermal environment and its associated temperatures is not universal across TIC manufacturers. For example, the majority of fire service TICs (there are some exceptions) do not show colourization until the TIC switches to Low Sensitivity Temperature Mode. Unfortunately, when fire service TICs switch to low sensitivity and at what temperature they begin to show colour is not standardised nor universal. NFPA 1801 states that a fire service TIC shall follow the thermal-imaging basic colour format, which progresses from hot to cold in the following colour progression: black, grey, white, yellow, orange, red. Unfortunately, no two manufacturers are alike in regard to colour temperature correlation. For example, the following fire service TICs show colourization in low sensitivity temperature mode at the following temperatures:
- MSA 6000: yellow colourization appears at 1000°F/538°C in Low Sensitivity Temperature Mode.
- Drager UCF series (6000–9000 models): yellow colourization appears at 572°F/300°C in Low Sensitivity Temperature Mode.
- Bullard (all models): yellow colourization begins at 500°F/260°C in Low Sensitivity Temperature Mode.
- FLIR (K2-K65 models): yellow colourization begins at 300°F/148°C in Low Sensitivity Temperature Mode.
- Leader 3.3 model: yellow colourization appears at 392°F/200°C.
- Argus: yellow colourization appears at 300°F/148°C.
- Scott X380 models: this model has Tri Mode Temperature Sensitivity and breaks the overall temperature range into three spans (High, Medium and Low Sensitivity). Each Temperature Sensitivity Mode has a different colour temperature correlation.
In conclusion, this is only five of the numerous myths or misconceptions about fire service TICs that we have encountered in our travels. We encourage the reader to learn their specific brand of TIC, how to properly interpret the image, and to attend as much application training with their TIC as they can so they will be better prepared for the challenges of the modern fire ground.
For more information, go to www.insighttrainingllc.com
References
Amon, Francine. Bryner, Nelson. Hamins, Anthony. Lock, Andrew (2008). NIST Technical Note 1499 Performance Metrics for Fire Fighting Thermal Imaging Cameras – Small- and Full-Scale Experiments. NIST pp 36, 41.
FEMSA Manual (2015). Fire & Emergency Manufacturers Services Organization Inc. www.femsa.org. p. 2-4
NFPA (2018). NFPA 1971 Standard on Protective Ensembles for Structural Fire Fighting and Proximity Firefighting. NFPA. Section 8.1 Thermal Protective Performance Test. P.64.
Oberon Company (2005). Understanding the Stoll Curve. Oberon. Pg.1 Retrieved from: http://ebooks.bharathuniv.ac.in/gdlc1/gdlc1/Engineering%20Merged%20Library%20v3.0/GDLC/Understanding%20the%20Stoll%20Curve%20(3569)/Understanding%20the%20Stoll%20Curve%20-%20GDLC.pdf
About the Author
Andy Starnes is a Level 1 Thermography Certified Instructor and founder of Insight Training LLC.
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