Although the primary use of a thermal imaging camera (TIC) at a fire scene is to find sources of heat and assist with occupant searches, the uses of these cameras go well beyond just fire incidents. From basic training, we know that TICs can provide enormous benefits to aid in searching for persons at motor vehicle accidents and in urban search and rescue events, but how can this thermal technology benefit us at a hazardous materials incident?
Identifying and formulating an incident action plan for any required rescues should be the tactical priority and benchmark for such incidents. Considering the priority for rescues, if an exposed or affected person who may be experiencing an altered mental state has wandered away from the immediate scene, the crew assigned to search for this individual would benefit greatly in terms of time and efficiency if equipped with a TIC, especially during nighttime operations. This is one obvious example of the benefits of applying the TIC’s thermal detection capability at a hazardous materials incident.
With the management of any incident, the quality of information supplied can dictate the success or failure of the job. Relevant, current information is crucial when formulating efficient and effective tactics. The TIC can provide additional information for the incident management team (IMT).
By applying some creative techniques and understanding how objects interact with infrared energy, incident commanders (ICs) can accelerate incident resolution and reduce crew exposure. Below I will discuss some applications in which TICs can see the unseen and assist crews.
(1) The level of the container’s contents is made visible using a TIC. The upper section of air is heated at a higher rate than the liquid at the bottom. The upper section of air is warmer than the lower section of liquid and therefore produces a distinct indication of the level inside the container. The temperatures on the left indicate the temperature range the camera is showing; Sp1 is the container’s surface temperature. (Photos by author.)
(2) In a hazmat incident, the affected ground area will present differently. This is what you could expect the ground to look like after completion of decontamination or after a surface spill of liquid. Concrete surfaces tend to heat water up more quickly than grassy areas, which make this contrasting effect a little less obvious on concrete than on grassy areas.
Using a TIC, we can obtain valuable thermal spectrum information from storage tanks containing liquid chemicals that may not be obtained otherwise. Over the course of the day, most liquids absorb thermal energy at a rate slower than the air; at night, this process is reversed, with liquids giving off their absorbed heat at a slower rate than the air. The difference in heat release rates between the liquid and the air can make it possible to identify the internal liquid levels within the containers and therefore provide more information to the IMT. In some situations, this may be limited or not possible at all, depending on the tank’s construction or materials. Some containers are insulated and will show no indication of content levels. Others may use polished metals such as stainless steel; these surfaces will have high reflectance values and result in an incorrect interpretation of the situation because a number of reflections from nearby heat sources have been bought into the TIC’s view. In such circumstances, you may obtain information from other areas of the tank or container, such as the pipe fittings or the valves. Do the valves at various heights look different? Does the labeling where the surface is less reflective than the main tank material now show an internal level (photo 1)?
By determining the level of the contents within pressurized vessels, such as horizontal tanks that may contain liquefied petroleum gas (LPG), during fire incidents and continually reviewing these levels throughout the incident, an IMT can determine if a catastrophic event such as a boiling-liquid, expanding-vapor explosion (BLEVE) is imminent and then make the necessary tactical adjustments.
Likewise, solid chemicals (e.g., granulated chlorine) may also provide additional information when viewed using a TIC. Using the TIC to view these types of oxidizers is excellent for determining if an exothermic chemical reaction is beginning or is in progress. Again, this information may be extremely beneficial to the IC and may assist in identifying the chemical.
Drawing a line around a hazmat incident to determine the extent of the affected area is not easy. Unlike managing a structure fire or wildfire where we can see visually where the fire extension is, information regarding hazmat spills may not be so obvious. The chemical plume size combined with wind direction and speed will certainly be a factor in determining the scene size. The spill size, combined with any active water runoff, can also be an IC’s headache in determining the placement of any exclusion zones (photo 2).
When implementing any tactical actions, consider if these actions are going to contribute to the problem and hinder the safe and quick resolution of the incident. For example, if current tactics, based on scientific advice, require using water to suppress any chemical reactions, is this water likely to flow into a natural waterway or drainage system? Are we now about to contaminate the surrounding ecological systems? Performing regular scene appraisals using a TIC may show what’s actually happening.
TICs collect infrared energy from the surfaces of objects and then visually display the varying levels of intensities to the operator. How well an object presents this heat to the TIC depends on that object’s emissivity. Objects with high emissivity properties (usually dull, nonmetallic objects) will display a more accurate account of what’s happening. Objects with low emissivity attributes tend to be more reflective and can introduce other nearby sources of heat to the display. Liquid chemicals’ emissivity properties will likely differ from that of the ground where the spill occurred and hence be likely to display quite well on the camera.
When using a TIC correctly, the ability to see a liquid in contrast with the ground provides a good indication of the extent and size of the spill. You can also monitor the spill to determine whether it’s extending and if the spill is following the terrain toward any nearby waterways. If the spill size decreases over time, you may need to question whether this is because of evaporation or because of ground absorption. This could be another clue of the chemical properties. Again, the more information we have, the better the chances for a smooth incident resolution.
Because a TIC can see only infrared energy, a distinct difference in the temperature or emissivity between the ground and the liquid is crucial to provide a clear image. If the ground temperature or emissivity is similar to that of the liquid, it may not show the size or location of the liquid well. It’s unlikely that they will be a perfect match and not show any effects, but as shown in the image of the decontamination process that is occurring on the cement (photos 3-4), the effect isn’t as dramatic as when this process is undertaken on a grassy area (photo 5).
(3-4) A TIC image shows decontamination water clearly on the concrete surface. The brighter areas of the image are where the water has been applied. You can use this to evaluate the coverage of the decontamination process.
Liquid pooling on the ground and ground absorption should show clearly on the camera, possibly enabling you to detect underground leaks with the TIC. A number of factors can affect how well this process works; it depends on any differences between the surrounding unaffected terrain and the affected area, the ground temperature vs. that of the substance, and the emissivity of the chemical and that of the ground. Substantially sized underground pipes transporting liquid that may be leaking could pose an imminent risk of causing ground slippage or collapse since the increased moisture levels have changed the soil’s stability. This moisture should show up within the infrared spectrum as an area of interest. Countless drone contractors use this same principle to monitor public spaces such as golf courses and public parks for any water leaks.
The valves within a pipeline system may also be a failure point and produce leaks. Depending on the piping system’s design, the amount of pressure within the system, and the characteristics of the material that is being piped or stored, they may all present differently on a TIC. Steam will display as an area of heat while other products that are normally a gas at room temperature but are being piped as a liquid will display as a cold area at the leak site.
(5) The decontamination water is clearly seen in this image of a grassy area.
Once crews have been within the prescribed exclusion zones and after any departmental procedures, you may need to undertake on-site personnel decontamination. Again, TICs can fill a niche role to assist in monitoring decontamination for effectiveness. The overall objective in any hazmat response is to render the situation and area free of any danger. There is little point in having crews move the chemicals from the immediate spill area to the assigned decontamination area with no way to determine the contamination at the decontamination area.
Using a TIC during decontamination, you can easily see how any runoff from decontamination is affecting the terrain and look to develop a plan for any land rehabilitation in the future. Photos 3-5 clearly show the presence of water and how it has affected the ground just after a short period of decontamination. Expand this process to a large chemical incident, and you can begin to imagine how this can become a serious IMT consideration.
When implementing any firefighter decontamination method, consider using the TIC to monitor the process. As the water flows over the firefighter, it will display areas of contrast against the areas that are not. This could enable you to make the decontamination process more efficient and effective.
You are not likely to have much success in viewing the gas or product directly using a standard TIC; you would need a specialized optical gas imaging camera that is designed to view the specific spectral ranges of specific gases. If this type of camera is unavailable, the TIC operator needs to think creatively and look for the indirect effects of the leak on the surrounding objects and structures, which may indicate the leak location. The adiabatic process of a gas that is now pressurized into a liquid, when rapidly released, can reduce the temperatures of the nearby valves or pipework and will show quite clearly on the TIC display.
Think of a self-contained breathing apparatus cylinder when you rapidly let the contents out (lots of flow, big pressure drop); the valve assembly will begin to ice. In a steam release, the temperatures would be elevated. Pay careful attention if pipework or valves have some sort of insulating system present such as foam or fibrous material; this may hide any temperature difference.
With the advent of small unmanned aircraft systems (sUASs) and the optical and thermal imaging abilities now available, the scene as a whole can be viewed and recorded. By continually observing the scene from above using both the optical and thermal imaging systems over the incident’s duration, you can develop valuable timeline data, inform the IMT as the incident unfolds, and aid postincident analysis.
Using an sUAS, you can monitor waterways for real-time runoff; monitor crews for safety; and efficiently establish hot, warm, and cold zones. For example, if you can determine that the liquid runoff has ceased flowing and is being contained effectively, you may be able to reduce the size of the exclusion zones and therefore reduce the travel time for crews traveling to affected areas in unnecessary personal protective equipment. Also, the data sUASs provide will be valuable in evaluating the effectiveness and efficiency of the incident’s management and be helpful in any future court proceedings. If an sUAS is unavailable, alternatives such as deploying aerial apparatus that have thermal imaging capabilities incorporated into the appliance or a firefighter with a TIC may provide the same overall perspective of the scene.
The angle at which you view a scene can also alter what you see. Viewing the scene from ground level may show areas that appear to be of interest but are actually reflections from nearby objects. It’s important to view an area or an object of interest at an angle that is as close to perpendicular as possible. As you would have learned in fundamental TIC training, you can confirm if the object is or isn’t a reflection by moving and viewing it from a different angle. If the object moves, disappears, or substantially changes, chances are it’s only a reflection.
Whenever using firefighting TICs, recognize and account for their limitations. A TIC operator must look at what he is seeing and then discern what appears normal and what does not, a qualitative assessment. TICs that have been developed for fire service use don’t allow the user to adjust the required settings to allow for accurate temperature readings, so don’t rely on the temperatures that a TIC shows.
Ensure that the TIC you are using is suitable for the environment. Most TICs aren’t intrinsically safe and therefore are unsuitable for use in explosive atmospheres. Although some are, the operator must understand in which environments the camera is able to operate. If considering using a TIC at your next hazmat response, consider where and how you want to use it and if it’s safe to do so, and seek any advice from scientific experts prior to use.
You can see how adding the layer of thermal imagery can assist in resolving hazmat incidents. Depending on your fire department’s policy and how it determines a hazmat incident is resolved, reviewing the documented TIC imagery may provide the evidence required to ensure scene rehabilitation has been completed properly. The TIC imagery and video can help you confirm the size of the contaminated area and that the contamination has been removed for any future litigation.
TICs are adaptable equipment that overall are low cost and don’t require specialized skills to operate. With creativity, an open mind, and an understanding of how this technology works, you can benefit by continually considering, “Would looking at this through a TIC provide a different perspective?”
JOHN BLACK is a full-time senior firefighter who has been based in Australia for the past 11 years. He has a level 2 certification in thermography and has a professional interest in training and furthering thermal technology use within the fire service and at incident operations.