Errant information related to thermal imaging seems to permeate the fire service. I am not sure what causes this, but it seems like several topics simply will not die and keep getting reintroduced. What bothers me most is that, often times, these inaccuracies are reintroduced to the fire service under the guise of training. In the past several months, there have been no fewer than 10 articles published or promoted to the fire service – by media and manufacturers alike – that cover the topic of thermal imaging. All of them contained inaccuracies. Some are opinions stated as fact, while others are factually incorrect.
I would like to set the record straight regarding the five most common myths surrounding thermal imaging. I have covered each of these topics in more depth in previous columns, so I will only scratch the surface of each topic in this column.
Myth 1: Temperature sensing is accurate
This is nonsense, and you should confront it at every opportunity. The right way to phrase this is, “Temperature sensing is sometimes accurate enough to be relevant to decision making.” What’s the difference, you ask? Well, even under controlled laboratory conditions, radiometry (temperature sensing) is only marginally accurate, often to a plus or minus 10 percent. But when temperature sensing is inaccurate, it is often wildly inaccurate. This is not a statement about the quality of the thermal imager.
The primary causes of inaccuracies are well beyond the control of the manufacturer, but you could roll them all under one umbrella called “real life.” Real life is not a lab. Real life is full of smoke, extreme heat, shiny surfaces, super-heated gases, condensation and the like – all of which contribute to inaccuracies. Temperature sensing is not valueless; rather, it must be taken in context. Please remember that it can be wildly inaccurate, even under rather mundane, real-life circumstances.
Myth 2: Image freezing
Nearly every thermal imager sold today is of a microbolometer technology, but there are still many of the barium strontium titanate (BST) technology imagers in use. Don’t confuse yourself with what each means (see Myth 4 below), but suffice it to say that these two technologies make up 99% of all thermal imagers in the fire service today, and they behave very differently.
Both technologies must periodically calibrate their respective thermal sensors; however, microbolometers use an internal shutter to do so and a BST does not. Microbolometers offer a multitude of advantages over BST in terms of size, power consumption, durability, dynamic range, electronics integration and others, but one drawback is the utilization of a shutter for calibration. When the shutter closes – known as non-uniformity correction (NUC) – all incoming heat is blocked and the imager is blind for a split second. While the imager is blind, the image seen immediately prior to the NUC is frozen on the display. There is nothing you as a firefighter can do to make this stop or make it faster. NUC occurs at two times:
1. Whenever the thermal imager changes gain states from high sense to low sense or from low sense to high sense. When the imager is exposed to very high heat sources, it must turn its internal gain state down to what is known as low sense; however, when viewing less-intense heat sources, the thermal imager must turn its internal gain up to what is known as high sense. This allows for consistency of picture quality, but requires a calibration and an NUC.
2. Whenever the imager itself thinks it needs to. Left alone in a room, staring at a mundane, ambient scene, the thermal imager will NUC at fairly regular intervals and differ by manufacturer, but routinely in the range of every two to four minutes. When exposed to more dynamic scenes, however, the imager will NUC more often.
While at times inconvenient, NUC is necessary to make sure the image is of high quality and accurate in what it displays.
Myth 3: Image quality is everything
Image quality is not everything. Image quality is one thing. Having and using a thermal imager is everything. Each department must make its own decisions about what is most important. Image quality is important as is durability, size, battery life and other considerations; however, no feature is universal, and no feature will satisfy everyone.
Thermal imagers are a major expense for many departments, and most fear buyer’s remorse after the purchase. Most departments want to buy the very best thermal imager they can afford, but I have seen many departments bypass the opportunity to buy an imager because they could not afford the best image quality. Any thermal imager is better than no thermal imager. Image quality is often the primary cost driver in a thermal imager, and it is overrated. If you can afford better image quality, then by all means buy it; however, every thermal imager manufactured for and sold to the fire service has sufficient image quality for navigating a structure, locating victims and identifying secondary means of egress. I don’t care if you go to eBay to buy an imager that is 10 years old if that is all you can afford because even the image quality of a 10-year-old imager is better than no thermal imager at all.
Myth 4: Thermal imaging is complicated
Thermal imagers are technical and complicated. Thermal imaging is neither. One of the best things about a thermal imager is that it is extremely intuitive for the most common tasks such as navigation, victim location and egress. When my kids were smaller, they used to play hide-and-seek with thermal imagers at home (one of the perks of the job) and with no instruction at all they quickly figured out how to spot footprints on the floor in order to find where the other one was hiding. They never questioned navigating. It simply wasn’t an issue.
I am not proposing that the stakes in firefighting are not higher than hide-and-seek; rather, I am trusting that no firefighter would ever enter a structure without being trained in the basics of firefighting. Thermal imagers should never replace basic firefighting skills, but don’t get caught up in the technology trap. If you are interested in how thermal imagers work, then seek the knowledge, but don’t fall victim to the belief that thermal imaging requires extensive, advanced training to use. You should always take advantage of training if you can find it, but using a thermal imager is not complicated.
Myth 5: “I don’t need a thermal imager”
Of course you don’t. Twenty years ago, long coats and high boots were sufficient, and you did not need full turnouts. You don’t need a thermal imager. You can definitely fight fire without them. The question is: “Should you?”
Why would you not take advantage of the ability to see in an otherwise pitch-black environment? Why would you bypass the opportunity to locate a victim faster? Better yet, why would you bypass the opportunity to find one of your own faster? If you were the one trapped and calling a Mayday, would you want your rapid intervention team using a thermal imager? I would. Is it necessary to use a thermal imager to rescue a downed firefighter? No. Is it preferable? Unequivocally.
Again, covering these topics is not meant to be deep. Of course, there is more to talk about on each one; however, as the technology and utilization matures, so too must the understanding. When a technology approaches ubiquity, some buyers take their eye off the ball and fall victim to hype.
As with anything, strive for common sense and sound judgment. If you don’t understand something, seek answers. In the face of a claim that does not pass the sniff test, ask for proof. Challenge everything. Myths and misstatements are standing in the way of broader adoption, and we simply should not stand for this. After all, a firefighter’s life may depend on it.