Current thermal imagers are based on technology that was originally developed for the military. Thermal imaging technology provides the ability to see and target opposing forces through the dark of night or across a smoke-covered battleground. The properties that have made infrared detection valuable to military services around the world also make it valuable to fire services and law enforcement.
In the late 1950s and 1960s, Texas Instruments, Hughes Aircraft, and Honeywell developed single element detectors that scanned scenes and produced line images. The military had a lock on the technology because it was expensive and had sensitive military applications. These basic detectors led to the development of modern thermal imaging. The pyroelectric vidicon tube was developed by Philips and EEV in the 1970s and became the core of a new product for firefighting, first used by the Royal Navy for shipboard firefighting.
In 1978, Raytheon R&D group, then part of Texas Instruments, patented ferroelectric infrared detectors, using barium strontium titanate (BST). BST stands for barium strontium titanate, the material that coats the thermal imager’s sensor. Raytheon first demonstrated the technology to the military in 1979. In the late 1980s, the federal government awarded HIDAD (HIgh-Density Array Development) contracts to both Raytheon and Honeywell for the development of thermal imaging technology for practical military applications. Raytheon went on to commercialize BST technology, while Honeywell developed vanadium oxide (VOx) microbolometer technology. Later federal programs such as LOCUSP (Low Cost Uncooled Sensor Program) provided funding for both companies to develop their thermal imaging technologies into equipment systems, including rifle sites and drivers’ viewers. After the 1991 Gulf War, production volumes increased and costs decreased, and so introduction of thermal imaging to the fire service ensued. In late 2004, Raytheon’s Commercial Infrared Division was sold to L-3 Communications.
Meanwhile, the Honeywell microbolometer patent was awarded in 1994. Boeing, Lockheed-Martin (who sold its infrared business to British Aerospace, or BAE), and others licensed VOx technology from Honeywell and developed infrared detectors for military applications. Thermal imagers based on both BST and microbolometer technologies are available now for non-military applications. In fact, thermal imaging has now expanded to be used in firefighting, law enforcement, industrial applications, security, transportation and many other industries. Bullard introduced it’s first thermal imager specifically designed for fire fighting in 1998.
Hands-on training and then a follow up explanation is a quick drill style approach that lends itself to shorter, more frequent training. And while it is in no way meant to replace traditional classroom learning, there are a few quick drills that can be used daily and in less than 15 minutes to provide firefighters with a greater understanding of the technology they use. Let’s look at some quick drills for thermal imaging cameras.
1) Identifying “Heat Signatures”
Heat signatures can take on many different forms from the in-your-face obvious to the more subtle indicators. Most firefighters think of “big heat” when they think about firefighting or thermal imaging and then fail to notice less-obvious heat signatures; however, there is much to be learned from the smaller heat sources.
Somewhere in the fire station, place a space heater on the other side of a closed door. A solid core door will work the best but really, any door will do. Give the door some time to warm up. The door should develop a V-shaped “heat signature” on it.
You may have to play with the temperature setting on the space heater or even boost the space heater up by placing it on some sort of non-combustible item to get the look right. Have the firefighters conduct a search and see if they recognize the heat pattern prior to opening the door.
Whether they notice it or not, you can use the opportunity to talk about the benefit of recognizing smaller heat sources. If you have both solid core and hollow core doors in your station, you can set up several space heaters to show the difference between these different door construction types.
2) The Effects of Reflections
Reflections can create confusion and disrupt otherwise well-laid plans. While you cannot plan for every possible scenario, creating awareness is at least a step in the right direction. Fill the shiniest pot you can find with water and place it on a burner of the stove with the burner on high. Grab a cast iron skillet and place it on a burner immediately next to the shiny pot and turn that burner on high as well. Wait for the water to boil and the skillet to get hot. You are now ready to go.
Everyone knows that water boils at 212 degrees; however, when you use temperature sensing and point the crosshairs at the side of the pot, the temperature will read well below that. This is because of the reflectance of the outside of the pot.
The TI is reading the reflected temperature of the room rather than the temperature of the pot. Now look at the reflection of the skillet on the side of the pot. You should be able to see the colorization (if your imager is so equipped) or the extreme white of the skillet in the pot. If you place the crosshairs on the shiny pot where you see the reflection of the skillet, the imager will read the temperature of the skillet in the reflection from the pot.
Reflection can further be exhibited by other bright and shiny objects. The side of the fire apparatus, a dry erase whiteboard and most smooth tile flooring will all lend themselves to a mirror-like appearance if encountered with a TI.
In a fire, this can be a help or a hindrance, depending on the situation, but make no mistake – you will encounter them in a fire and if you will encounter them in the real thing, then you better make sure you encounter it in training first.
3) Thermal Latency
Ask several firefighters to sit or lie down on the furniture and assume different positions. Let them stay there for several minutes and then tell them to get up. What you will see is the amount of body heat that the furniture absorbed and is now re-emitting.
This latent thermal effect can be used to show that a firefighter, during search and rescue, may see “signs” of victims before they actually locate any. There might be latent thermal images on furniture or beds which can be indications that victims are present. This can also be used on car accidents to assist in determining the number of occupants especially in rollover accident where ejections are more common.
You can get both false positives and false negatives so information from thermal latency is only one piece of information, but if you happen to have a driver of a vehicle who is intoxicated and head injured mumbling about a passenger and you see a thermal latent imprint in the passenger seat, I would make sure that you search the surrounding area.
If you have access to them, grab a chemical hot pack, activate it and throw it on a table. Show the group what the hot pack looks like to the thermal imager, and then cover it with a thick blanket. This shows that victims on beds are hard to detect as the warmer the blanket is for people, the better insulator it is. The better insulator the blanket is, the harder it is for a TI to “see.” You can even use a bed sheet, blanket and comforter. For this reason, all beds should be searched by a gloved hand regardless of what the TI says.
5) Fire Inspections and Pre-plans
One of the easiest trainings to conduct is to simply take the thermal imager with you during company-level fire inspections or pre-plans. Use the thermal imager to look around the building and if you see something that you do not recognize, investigate it until you understand what is causing it and why it appeared the way that it did on the thermal imager. Building this kind of mental database is one of the most effective methods of understanding what the imager is trying to display.