Thermal imaging: breaking down the scan – Part 3

Firefighters are preparing to make entry but are scanning the environment to gain more information prior to making entry. Images supplied by Author / Contributor

Thus far, we have learned how to properly interpret thermal data during a scan, we have learned how to conduct a scan during size-up, and now we will complete this series by explaining how to scan the interior environment. These concepts will assist firefighters in enhancing their overall fire ground effectiveness.

Interior size-up scan

A firefighter should also continually assess the interior of a fire environment as they progress towards their desired objective. This can be achieved by breaking the structure down into compartments or boxes. Each compartment is scanned prior to entry and the information is communicated to the fire-attack or search crews. The company officer should assess, communicate and then monitor conditions as they progress. This scan is recommended to be done in the same format as mentioned earlier, but the firefighter will be looking for different areas of concern or interest.

First, scan low: Firefighters are often taught the following phrase when scanning/assessing the fire environment. Look for Life, Look for Fire and Look for Layout. However, how is a firefighter to adequately assess an environment with limited to zero visibility? If the firefighter has conducted a Tactical 360 size-up, they should have a better idea of the fire’s location, severity and possible direction of travel. Once the entry point is determined, the company officer or crew leader should scan low at the entry point in the sideways grip or gangster grip so they can see all three areas in one view. If the TIC automatically switches to Low Sensitivity when the scan is being conducted low, this is an indication of high heat. The firefighter should not disregard this.

By scanning low, the firefighters were able to identify the victim in the furthest point of the room. In many cases, firefighters start their scan high and miss important details such as the victim. Images supplied by Author / Contributor

When scanning low, the company officer should note areas where the victim may be, the location of the fire and the layout of the room. When the TIC is down low, it is also typically in a lower-temperature environment, allowing it to stay in High Sensitivity. High Sensitivity by definition equates to higher sensitivity to details in lower temperature environments, which are generally under 300 degrees.

In addition to looking for life, fire and layout, we have added some important areas that firefighters should note when using the TIC to scan/assess the environment:

Overall level of heat: How much heat is in the room? If the temperatures are over 300 degrees (A class II Thermal Environment), a firefighter’s PPE will start to degrade. In addition, if temperatures are above 200 degrees Fahrenheit, they are not tenable for a victim. Firefighters must not only extinguish the fire but identify the heat and remove it as they move toward their desired objective.
Thermal layer & pyrolysis: When assessing a compartment, the firefighter should be well acquainted with his/her TIC and how and when it displays elevated temperatures. As shown in the following two images. A firefighter relying solely on the optical view would be in for possible contact burns or worse by crawling across this floor. In addition, firefighters were taught not to crawl past fire. By assessing the compartment, we advocate not to crawl past heat or superheated fuels. The modern-day fire environment consists of high-heat-release-rate fuels made mostly of petroleum-based products. These are potential energy bombs waiting to light off behind firefighters when the process of pyrolysis isn’t stopped or interrupted.

While scanning low, firefighters should be aware of possible hazards such as fire below or beneath them. There have been several studies done showing that TICs cannot see through floors or judge floor integrity. However, through thermography we can learn to assess these conditions in ways that these studies failed to grasp or understand.

Optical view of a couch on fire in a small room. Images supplied by Author / Contributor

Example #1: A fire beneath the floor of a mobile/manufactured home. In this photo, firefighters were alerted to a fire beneath the floor due to the conductive nature of the metal floor-support joists in this type of home with thinner insulation components for the flooring. The obvious heat signature between the floor joists along with the heat signature from the floor register caught their attention.

Example #2: Holes in floors. In many cases, holes in floors in a fire environment can be difficult to see due to the thermal equilibrium or bland scene nature of the environment. However, when looking for holes in floors firefighters can see signs or clues of these concerns by looking for irregular patterns that are either dark or have heat signatures/convection currents coming through them.

Second, scan middle height: As the firefighter scans the entire room, it is important to note that they scan from one wall to the opposite wall covering the entire width of the room. Many firefighters fail to scan the entire room due to the lack of flexibility within their protective ensemble. With the increased stress of having to perform actions quickly, this also causes the scan to be literally ‘short-sighted’. As the firefighter scans across the middle of the room the field of view of the TIC will also show the upper portions of the ceiling area, which can aid in their overall assessment. The company officer or crew leader completing the scan must be familiar with their TIC and when it shows colorization, when it switches to low sensitivity, and identify convection currents. Areas of concern that should be noted are as follows:

Descending thermal layer
TIC in Low Sensitivity Mode
Fast moving convection currents
Superheated fuels

In the top photo, provided by Project Kill the Flashover, we can clearly see a descending thermal layer. The TIC has switched to Medium Sensitivity (equivalent to Low Sensitivity in most TICs). Superheated fuels and fast-moving convection currents are seen in the following video moving towards the open front door (https://youtu.be/9Nik1UMlaAw). As shown in the second photo, this is a zero-visibility training environment with a descending thermal layer that is between 300 and 599 degrees Fahrenheit apparent temperatures. Without a proper scan and interpretation of the thermal data this would have been missed.

Thermal view of the couch on fire in a small room. Notice the importance of thermal data! Images supplied by Author / Contributor

Provided by Project Kill the Flashover, we can clearly see a descending thermal layer. Images supplied by Author / Contributor

Thermal Image of heat transfer (thermal bridging) from a fire underneath the home between the floor joists. Notice the heat being transferred through the floor register vent in the upper left corner of the image. Images supplied by Author / Contributor

Thermal image of the fire room that clearly shows the thermal layer descending downwards toward the high heat release rate fuels in the room. This photo was taken seconds before the fire transitioned to fully developed state. Images supplied by Author / Contributor

This photo is a side by side comparison showing the thermal view on the left and optical view on the right. Firefighters who base their decision on what they can see optically are limiting their overall effectiveness by not including thermal data. Images supplied by Author / Contributor

Third, scan high: As the company officer scans the uppermost portion of the environment the context of the environment will determine the criteria of their assessment.

Residential context: Residential ceilings can be higher but in many cases are between 8ft and 10ft in height. In many residential structures the preferred linings or compartment walls/ceilings are gypsum/sheetrock, plaster and lath, or a combination of wood panelling and plaster. In the top photo, a wooden bead board ceiling is shown. This particular TIC is equipped with image enhancement and meets NFPA 1801 compliance, which states that ‘Colorization shall overlay the grayscale thermal images produced by the thermal imager. Details within the thermal image and within the colorized area shall remain resolvable by the user other than at saturation.’ These are all high-emissive materials ranging from 0.7 to 0.9 in Emissivity ratings that will emit heat very well. Fire Service TICs are pre-set at 0.95 to 0.97 emissivity, which is the most common rating for carbonaceous materials. Therefore, the TIC will detect heat quite well from these types of surfaces. A well trained TIC operator can identify heat in the ceiling area that can assist with determining if there is fire above them, fire is localized to the compartment, and if the ceiling joists above them are failing.

The thermal layer is clearly visible over the firefighters head and details within the colorized area are resolvable per NFPA 1801’s requirement regarding colorization. This provides firefighters more information about the structure itself. Images supplied by Author / Contributor

A lath and plaster ceiling prevented the firefighters from detecting the heat between the ceiling and space between them and the second floor. Once the ceiling was removed, the area of interest could be identified. Images supplied by Author / Contributor

In this photo, we can see the benefit of image enhancement and how the TIC exceeds NFPA’s requirement that states ‘Details within the thermal image and within the colorized area shall remain resolvable by the user other than at saturation.’ Images supplied by Author / Contributor

A firefighter was able to identify this Bowstring Roof Truss system from the interior during the high portion of their scan of this open floor plan of a commercial building. Images supplied by Author / Contributor

Large area context: Great rooms or commercial spaces can have very high ceilings, drop ceilings that mask or hide heat, or large open spaces that can have an infinite number of ceiling coverings or lack thereof. Drop ceilings are designed to insulate and cover non-aesthetically appealing infrastructure such as ductwork and wiring. There have been many fires in structures with these types of ceilings where firefighters were unaware of a fire burning above them. It is important to note that if an object is designed as an insulator, it will hide heat or mask it from the TIC’s view in many cases. As always, a scan with a TIC doesn’t replace an investigation; it only assists in diagnosing areas of concern.

Open commercial spaces with various types of roof construction: In many cases, commercial or even old mill-type structures converted into residential structures will have open ceilings exposing the roof support systems. Firefighters can scan the ceiling and identify the components and if they are intact. This is not to say that they can verify the structural integrity as much as they can use the TIC to identify the roof type and determine if the location of its structural components is in the proper place. As shown in the bottom right photo, this building has a bowstring roof that was not readily apparent from the exterior but identifiable by scanning with the TIC.

Summary

The goal of this article is to provide more in-depth information to those who are making a difference on the fireground and incorporating the TIC into their skill sets. This is not a comprehensive list of all items, considerations, or concerns when scanning with the TIC. However, it is our goal to provide experientially relevant information that the firefighter can read, learn and apply today.

Firefighters who learn their TIC, the key attributes of thermal imaging and the context of their environment will be able to enhance their decision-making skills by seeing the unseen and making a difference like never before. As we teach our children to look both ways before they cross a busy street, so should we teach firefighters to look, assess and communicate the hazards they see to their fellow firefighters to properly mitigate the hazards before them.

For more information, go to www.insighttrainingllc.com