Fire Services Journal of Canada, March/April 2003
The Many Uses for the Thermal Imager
By Jonathan Bastian
The North American fire service is always looking for new, creative ways to do its job safer and more effectively. Some of these innovations are clever adjustments to a piece of metal (such as a Halligan bar), while others are dramatic changes in philosophy or technology. Thermal imaging is one of the newest technologies in the fire service. Based on its rapid growth, thermal imaging appears to be one of the best-received and most rapidly implemented innovations in decades.
While the great interest in thermal imaging continues to expand, the United States’ Federal Emergency Management Agency recently reported that only one-fourth of all US fire departments have a thermal imager (TI). Anecdotal evidence indicates the ratio may be even lower in Canada. This article will briefly explain the technology as well as how fire departments across Canada can put it to effective use on a regular basis.
The Technology
The current fire service TI uses military technology in use for years. This technology detects infrared energy and converts it into a visible image on a display. Militaries around the world use infrared (IR) detectors to allow their forces to see and target opposing forces through the dark of night or across a smoke-covered battleground. The properties that made IR detection valuable to military services also make it valuable to fire services.
IR is a portion of the electromagnetic spectrum, which ranges from gamma rays and x-rays, through visible light, past infrared and microwaves to radio waves. The energy’s wavelength determines placement within the spectrum. As the wavelengths vary, so do the properties of the different types of energy. IR is a portion of the electromagnetic spectrum that humans normally perceive as heat.
Visible light has a wavelength of 0.4 microns to 0.7 microns. This wavelength is susceptible to interference from small airborne particulates, such as smoke and fog. IR has a longer wavelength than visible light, covering 1.0 micron to 100 microns. (Fire service TIs operate in the 7.0 to 14.0 micron range.) This wavelength is not easily reflected by small particles (such as particulates in smoke or fog), and therefore IR can essentially “weave” through the particulates in smoke and fog to reach the detector (the IR receiver, also called a focal plane array or FPA).
Another way to understand the difference between infrared energy and visible light is to compare the TI and the human eye. The FPA and the eye are both receivers. They receive energy (IR or visible light) and convert it into an image our brains can interpret. The FPA receives wavelengths of heat energy called “infrared” while the eye receives wavelengths of energy called “visible light.”
The Structure Fire
Overall, structure fires are probably the most common and most understood application for thermal imaging. The first opportunity for TI use at a structure is incident size up. Many company officers perform a “walk-around” when first-in so that they develop an overall view of the structure and situation prior to committing firefighters inside. Performing this task with the assistance of a TI may give the officer additional information not available to the human eye. For example, Engine 5 arrives first at a single-story, wood-frame residence. Heavy smoke is pouring from the basement. During the walk-around, the officer’s TI shows him the image in Photo 1. This photo clearly shows high levels of heat racing up a void space between the wall studs. As a result, prior to entry, Engine 5 knows that the basement fire has already worked its way towards the attic. The company officer and incident commander can then assign resources appropriately, and safely, to ensure that the basement fire and its extensions are extinguished rapidly.
Photo 1: On the TI display, white is relatively hot. This image shows significant heat running up the void space between the wall studs. Because the heat stops suddenly in two of the spaces, there may be fire-stops. Photo courtesy of Bullard.
The next opportunity for TI use is during fire attack. If the hose team uses a TI while advancing its line, it can find its way to the seat of the fire more quickly and more safely. Because the team can see walls and objects using the TI, they can crawl through the most maze-like residences or occupancies with greater ease and improved safety. In heavy smoke conditions, the suppression company can use the TI to help identify which room is on fire. The company could also find access to upper and lower levels more quickly.
Ventilation is another aspect of the structure fire where TIs can assist firefighters in doing their jobs more effectively. At larger structures, the TI can help firefighters ensure that any ventilation holes in the roof are near the areas of highest heat. Additionally, at any structure, the TI may help identify compromised roofing before a company is committed to the roof. Because superheated gasses are visible on most TIs, the technology can help firefighters verify that a vertical ventilation point is performing properly.
The most common argument for TIs is search and rescue. A number of independent studies have shown that TIs improve search speeds by up to seventy-five percent and can more than double search success rates. While search and rescue may be the most frequently discussed application, it may be the least frequently used. Many fire departments do not have enough TIs or have placed the TIs in areas that are hard to access. Many fire departments keep their sole TI on the one truck that goes to every fire, such as a squad or ladder. By the time this company arrives, the primary searches are already underway. TIs stored in compartments most likely will stay in compartments until overhaul, when the tools in that compartment are needed. To have an effect on search and rescue efforts, the TIs must arrive early in the incident and they must come off the apparatus with the firefighters.
Many departments use their TIs successfully in overhaul. The TI can identify hot spots to help focus overhaul efforts, limiting collateral damage. Focused efforts also ensure that firefighters use their energy efficiently while greatly reducing overall on-scene time. For firefighters to gain the most use out of their TIs, they must know how to use them in areas that exhibit “thermal saturation,” which occurs when everything in the viewed area is very warm (such as a room after the fire is extinguished). The TI will then display everything in varying shades of light gray and white because everything in the scene is warm or hot. In this situation, firefighters need to use properly the other features of their TIs (such as thermal throttles, EI modes or pyrometers) to identify the hottest spots.
The Safety Aspect
Throughout the course of any incident, a TI may enhance firefighter safety. One of the most prominent capabilities related to safety is that the TI helps the firefighter monitor structural integrity in low-visibility conditions. The imager may confirm that a building has truss-roof construction, it may show damaged or missing trusses and it will help firefighters identify holes in the flooring or high heat below them. With proper training, firefighters can even identify the thermal layer and possibly recognize pre-flashover conditions, avoiding injury by “seeing” the danger coming before it fully engulfs them. Different IR detectors will “see” the superheated gasses of the thermal layer differently, but firefighters can train to recognize them. Photos 2a and 2b demonstrate how TIs can show superheated gasses, as well as how quickly conditions can change even if firefighters are equipped and experienced with TIs.
These images also illustrate how TIs can foster dangerous overconfidence. The firefighters in this incident are standing, violating a basic rule of firefighting. The intense heat from a diesel-fueled fire not only forces them to the floor, but it drives the firefighters from the area in a few dozen seconds. Firefighters must always remember that TIs are valuable tools, but they do not make people invulnerable or eliminate the need to follow basic firefighting safety practices.
(Note of Caution: These photos are from a Bullard TIx, a BST-based ferroelectric thermal imager. Other BST cameras could, and all microbolometer cameras will, display superheated gasses and thermal layers differently. Firefighters need to train on their own equipment to learn its behavior in live fire environments.)
Photo 2a: In a marine engine room, a firefighter approaches the stairway that leads down toward the fire. The ceiling is approximately 3.5 m above the gangway and has three 1.6 m2 vents open. The upper right corner shows the start of the thermal layer dropping as it banks down the corner of the room. Photo courtesy of Bullard.
Photo 2b: The same firefighter, in less than 2.5 seconds, already has the thermal layer dropping around his head (despite the 3.5 m ceiling and three open vents). In another second, the superheated gasses surround his entire body. The extreme heat forced the team out in under one minute. Photo courtesy of Bullard.
The Creative Applications
Not all fires occur in structures, so many fire departments have successfully used TIs for wildland firefighting. Outdoors, TIs can monitor personnel and vehicles to provide safety from fire as well as from vehicles moving in poor visibility. From an elevated position, a TI can help determine the exact fire line and monitor any hot spots. Because IR does not penetrate glass, firefighters using a handheld TI from a vehicle or aircraft must operate it safely through an opening.
Many fire department responses do not even involve fire. A hazardous materials incident can be an excellent opportunity to use a TI. If the vapor space above the material creates temperature differences that can be detected on the outside of the container, a hazmat team can identify the level of a liquid or solid material held in a container. These differences could allow the hazmat team to monitor or evaluate an incident that involves a sealed or pressurized container, such as a tanker trailer or propane tank. The hazmat team can also use a TI to identify spilled material, since it will likely have a different temperature than the ground or water on which it is spilled. This temperature difference makes it traceable and visible with the TI. In the right circumstances, concentrated gasses may even be visible to the TI.
Photo 3: Two 20-litre plastic pails show the TI that they are each about half full. Photo courtesy of Bullard.
What about TIs in EMS? Most fire departments actually respond to many more emergency medical calls than fires. They can use the TI to help any time the human eye fails. Rather than having firefighters and medics crawling on a factory floor or through a yard looking for amputated fingers, they can find the digits easily and quickly with a TI. At motor vehicle accidents, the TI could find ejected victims, even in heavy fog or at night. A department could use the TI to help rule out that a child safety seat was occupied prior to an accident. Just as the technology can help departments locate patients at an accident, it can also help them find a lost child in a forest or an elderly person who wandered away from a nursing home.
Training is another possible use for thermal imaging. TIs help firefighters monitor building conditions and trainee safety during live-fire evolutions. In acquired structures, building integrity can be monitored and in any live-fire scenario, dangerous conditions can be identified before firefighters are injured. Safety officers can identify firefighters at risk of high-heat exposure before their turnout gear is damaged or before they are injured by heat or steam. Almost all TIs available today can be equipped with a wireless transmitter. By connecting the receiver to a television and video recorder, the training officer and safety officer can remotely monitor and record the thermal images. The recording can be reviewed later for additional learning opportunities.
The Conclusion
Thermal imaging technology restores a firefighter’s sense of sight in the thickest smoke or darkest environment, with capabilities limited only by the creativity of the firefighter. TIs have proven themselves as critical firefighting tools for fire departments around the world, including many fire departments in Canada. In North America, however, TI usage is not as widespread as it should be. When properly used, TIs offer tremendous advantages to firefighters in a variety of environments. Firefighters must understand the need for this technology and then demand that they receive the appropriate number of these tools. They deserve nothing less.