By Carl Nix
When was the last time you responded to a hazmat call? Even if your department does not have a trained hazmat team, I’m guessing you have responded to one or more calls that have involved hazardous materials such as an overturned vehicle or tanker truck, a chemical emergency, or a meth lab fire.
Arriving on the scene of any one of these calls often forces firefighters to make decisions based on what they don’t see. Bring in a thermal imaging camera (TIC) and firefighters can now see what was previously invisible to the naked eye. Having this ability allows the firefighting crew to make better and safer decisions on the scene.
A TIC can be an invaluable tool for the hazmat firefighter. Having the ability to see the content level of an enclosed container at a safe distance is critical to the safety of the firefighting crew. Tracing a spill on the roadway in a rain storm is an environmental necessity. Seeing the gases of a container at a safe distance is critical to the safe outcome of a hazmat mission. More and more fire departments are being trained to answer hazmat calls, and the use of thermal imaging is another tool in their arsenal.
While a TIC cannot remove the hazardous materials at an incident, it can help firefighters locate and isolate the materials. Let’s look at how a TIC can help a firefighting crew at a hazmat incident.
Identifying a Land Spill
We have all responded to a scene where a vehicle was overturned and wondered if there were any materials leaking from that vehicle. Using a TIC in this situation allows the firefighter to detect the differences in temperature or emissivity (level of reflectivity) between the vehicle, its contents, and the ground surface around the incident. If the spilled material is a different temperature than the surface on which it is spilled and the material stays on the surface, it should be visible on the TIC.
If the product has already drained from its container prior to fire department arrival, a TIC can be used to identify the location of the contents that have leaked onto the surface. Be aware that there are factors that may influence how well a TIC will work in this situation, including the amount of product leaking or spilled, properties of the material, denseness of the vegetation where the spill has occurred, and the relative temperature difference between the spilled material and the surrounding environment.
Identifying a Water Spill
Using a TIC to identify a hazmat floating on a body of water can help firefighters identify where the material is entering the water supply and how much of the water supply has been contaminated. The differences in emissivity or temperature of the contaminant will allow the firefighter to see a visible difference on the TIC screen. It is important to note that only materials that weigh less than water can be identified using the TIC. A TIC cannot see through water.
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| 1 A thermal imaging camera is a critical tool in a firefighter’s arsenal when responding to a hazmat incident. (Photo courtesy of Bullard.) |
Identifying Product Levels in a Container
Materials in contact with the surface of a container can conduct heat through the walls of the container at a slower rate than the dead air space above the product. Unless the product was heated prior to being placed in the container, its level will be identified by a darker image (indicating cooler temperature) on the lower part of the container wall. The dead air space or vapor area will usually show as lighter on the screen of the TIC. If the container is insulated, it will not show the temperature difference.
To determine if a container is full or empty, use the TIC to scan other containers in the area to look for variations in color. The difference in color of the container may be attributed to a difference in material construction. When viewing containers or piping, remember that shiny surfaces can reflect heat from the surrounding area and give erroneous readings of the actual surface temperatures. The firefighter reading the TIC may be seeing a reflection of the heat of something in the background.
Identifying Gas Leaks
When firefighters are called to the scene of a gas leak, they can often smell the gas or feel it escaping under pressure, and they are often forced to employ gas detection equipment to find the point of origin. A TIC gives responders an additional tool to tackle this job. Most leaking gases will have a different heat signature than that of the surrounding atmosphere, allowing the TIC to identify the vapor cloud. Numerous factors will influence this capability, including the concentration or density of the gas, the temperature of the vapor in relation to the surrounding atmosphere, and whether the gas is transparent or opaque to infrared radiation.
When a gas escapes from a cylinder or pipe, it cools the immediate point of origin unless the gas is at an elevated temperature. The TIC sees the point of origin as darker than the rest of the picture unless variations in the environment prevent this, such as atmospheric variations including sub-freezing temperatures or man-made conditions such as heating.
The two most common uses of a TIC in hazmat incidents are tracking product spills and identifying product levels in containers. Practicing using a TIC for hazmat incidents is challenging, but below are three simulations that firefighters can try at the firehouse.
- Fill the kitchen sink with warm water, then pour a small amount of cooking oil into the water and watch it with the TIC. You should see two distinctly colored areas in the water showing the relative surface temperatures and determining the presence and flow of a material. After everyone has seen how lighter-than-water materials appear on the water’s surface, refill the sink and pour milk or juice into it. This gives firefighters the opportunity to see how heavy materials rapidly disappear from the view of the TIC.
- To see the effect of emissivity on a thermal image, partially fill several containers with water. The containers should be made of different materials, such as plastic, glass, and aluminum. Now, ask firefighters to view product levels in the containers by scanning them with the TIC. Firefighters will see how certain materials may hide heat differences better than other materials. Next, place cold, warm, and hot water in different containers to demonstrate which materials show product levels the best.
- To help firefighters practice identifying a leaking container, fill several containers with water and place them in a row. Make pinhole leaks in a container. Perform the drill in low-light conditions to force firefighters to rely on the TIC more than their eyes, aiding their image interpretation skills. While the TIC will not see leaking gases, it will identify a container that is cooler because it is leaking.
Fortunately, hazmat incidents are not frequent, but they are challenging. The use of a TIC increases the safety of everyone on a hazmat scene and helps to provide more accurate information so the incident commander can make better decisions.
Carl Nix is a 32-year veteran of the fire service and a retired battalion chief of the Grapevine (TX) Fire Department. He serves as an adjunct instructor for North Central Texas College and a thermal imaging instructor for Bullard. Nix has a bachelor of science degree in fire administration and is a guest instructor for Texas A&M Engineering Extension Service’s (TEEX) annual fire training in Texas.
