By Mike Richardson
Published Friday, September 28, 2012
| From the November 2012 Issue of FireRescue
Over the last 15 years, thermal imaging has slowly but surely become another “tool in the toolbox” for the fire service that is used on a daily basis for all types of emergency response. Both the thermal imagers themselves as well as the applications for which they are used continue to improve and grow on a daily basis. Although this growth is a good thing, it can also be a challenge to keep up with all of the progress and improvements.
This article will look at some of the changes that thermal imagers have gone through, as well as how those changes can impact their daily use in emergency response. The ultimate goal is to make sure that firefighters can understand the technical side of thermal imagers and how that technology can come into play in their daily use in emergency response.
Parts & Pieces
Fire service thermal imagers can be broken into five major operational components:
- Optical assembly
- Infrared detector
- Image display
- Power supply
- Imager housing
Let’s take a closer look at each of these parts, as well as some training tips that can help you and your firefighters become familiar with them.
One of the primary issues that firefighters need to be aware of with the optical assembly is the field of view (FOV). FOV is important to understand because it determines how much area can be seen at one time and it can impact depth perception. An imager with a narrow FOV can create tunnel vision and can compromise a firefighter’s depth perception by making objects appear closer than they actually are. Conversely, a thermal imager with a wide FOV can make objects appear farther away than they actually are. FOV numbers have varied greatly over the years and as new thermal imagers are put into service, it’s important to look at how the FOV changes can impact the use of the imager.
Practical Training Tip—“How much can I see?”
Place firefighters with a thermal imager in a room at one extreme end, have them look at the other extreme end of the room, and note how much of the room they can see with the imager. If they can’t see the entire end of the room, have them scan left and right and up and down, noting how far they have to move the imager to see everything. If the department has different imagers in service, complete the exercise with each imager and note how far each one has to be moved to see the entire area. Important: Ensure that all areas can be seen and checked for victims and hazards, and that firefighters remember to scan as needed to avoid tunnel vision while using the imager.
Practical Training Tip—“How Far Is That?”
Place firefighters with a thermal imager in a room with a zero-visibility environment. Starting 7 to 10 feet from a door, instruct them to crawl toward the door, using the thermal imager to judge distance, until they believe that they can reach out and touch the door handle. Based on the imager’s FOV, and the firefighters comfort level with depth perception, they may come up significantly short or almost run into the door before they stop.
If your department has different imagers in service, complete the exercise with each one and note the differences in where they stop due to the differences in FOV. Next, have the firefighters conduct the same drill, but add the use of a hand tool to help them judge the distance to objects.
At the “heart” of every thermal imager is the “engine,” or an infrared detector. This is the part of the imager that detects the infrared energy and processes it to produce an image. Over the years there have been a number of different detector technologies used, including PEV (Pyroelectric Vidicon Tube), BST (Barium Strontium Titanate), VOx (Vanadium Oxide) and ASi (Amorphous Silicon) Microbolometer detectors.
Microbolometer technology is the only one still available for purchase in fire service imagers. Contrary to many popular sales pitches, there’s no perfect detector technology; each type comes with its own strengths and weaknesses. As such, it’s very important for firefighters to have enough knowledge of the detector technology that they’re using; if they lack this knowledge, they won’t be able to take advantage of the technology’s strengths and avoid or work around its weaknesses.
Practical Training Tip—“How do I work with this technology?”
One side effect of how BST technology works is called “haloing.” A halo is ring or circle of an opposing color that shows on the display around a very hot or cold area. Although this could be seen as a con, it can actually be used to help identify the areas on the display that are at one temperature extreme or another. Photos 5, 6 and 7 demonstrate the halo effect.
A side effect of how microbolometer technology works is called “shuttering.” Periodically, the shutter will “fire,” blocking off the opening to the infrared detector. This process occurs so that the detector can auto-calibrate. Some thermal imagers have a visual indicator, which will alert firefighters that the shutter is firing; others don’t.
Per the two examples above, especially if a department is using thermal imagers with both types of technology, it’s very important for firefighters to identify the technology and understand in detail how it works. A firefighter who has been using BST technology and looking for halos, would not be successful if they switched to a microbolometer-based imager because that technology does not produce a halo. Likewise, a firefighter who started off using BST technology, and then switched to a microbolometer-based imager, might believe something was wrong with it when the shutter fired and the image froze on the screen.
Another area of thermal imagers that’s constantly changing: the display. Changes have included the size of the display and the information provided on the display. Display sizes can vary from 2½ to 5 inches. The key with display size on a thermal imager is striking a balance between size, weight and the ability to clearly see a detailed image. Some imagers are very basic and may have nothing on the display but a battery status indicator, while other imagers may have very extensive display features.
Practical Training Tip—“What can I actually make out?”
Start the drill by placing three firefighters acting as victims in a zero-visibility environment. Place one firefighter in the open, cover at least 50% of one firefighter, and cover the last firefighter completely, leaving only a hand exposed. Then instruct a fourth firefighter to view the area with the three “victims” using the thermal imager to see what they can identify. If the department has different imagers in service, repeat the drill with each one and determine the level of detail that each one of them is capable of indentifying.
Practical Training Tip—“What is all of that stuff?”
Ask firefighters to explain in detail each of the items that are on the display. Ensure that they can identify each item, as well as its significance and how they interact with it. It’s especially important to ensure that the firefighters understand what’s similar and what’s different if various makes and models of imagers are in use.
Thermal imager power supplies have seen a constant evolution over the past 15 years. The battery technology has seen a number of advances, starting with NiCad (Nickel Cadmium) and moving to NiMH (Nickel Metal Hydride) and LiIon (Lithium Ion).
The early NiCad batteries had a number of issues, including developing a memory (they will take less of a charge each time they are recharged unless they are completely drained each use) and limited operational times. If you have an imager with NiCad batteries, it’s important that the battery is completely discharged before it’s placed on a charger to prevent it from developing a memory. NiMH and LiIon batteries do not have issues with developing a memory, but they can be sensitive to temperature extremes. If they are exposed to extremely cold or hot environments, they may lose their charge very quickly.
Practical Training Tip—“Can I make sure the lights come on?”
Reports from the field have shown that in many cases when a thermal imager is needed the most, it’s not operational due to a dead battery. There are a number of areas that firefighters need to check to ensure that this does not happen.
- Battery service life: As with all rechargeable batteries, thermal imager batteries have a limited service life, ranging from 18 to 36 months. As batteries start to exceed 12 to 18 months of service, or if they are showing signs of significantly diminished operating times, they should be checked for serviceability. This can be done by using a battery analyzer or a volt meter to determine the maximum charge the battery is holding. Refer to the operator’s manual or manufacturer’s guidelines to determine if the battery is charging to optimal levels or if it needs to be replaced.
- Apparatus-mounted chargers: Whether the apparatus-mounted charger uses a connecting cable or direct contact system, it’s very important to ensure that it’s operating as needed each time the imager is returned for charging. Make sure connecting cables are disconnected completely as the charger is removed to prevent damage to the connector or wiring. With direct contact chargers, care must be taken to ensure the imagers are not returned to the charger dirty or wet, which can lead to corrosion and charging problems.
As the other components of a thermal imager have changed, the housing sizes and shapes have also changed to keep pace—and most firefighters would agree that one of the most positive changes was a reduction in both size and weight.
The size and weight of a thermal imager will ultimately dictate the carrying options available to firefighters, which can include full-size carry straps, short wrist lanyards and retractable keepers.
Practical Training Tip—“How can I hang on to all of this stuff?”
Have firefighters gear up to include all items that they would use for a structure fire, including full turnout gear, SCBA, radio, flashlight and imager. Once they’ve donned all of their gear, confirm that they can reach and operate all of the items as needed. Finally, ensure that they can have both of their hands free to carry out operations as needed, and they do not have to set a piece of their equipment down to make this happen.
Experience has shown that with all of the equipment firefighters wear and carry, it can be very challenging to manage all of it effectively. Real-world incidents have also shown that many firefighters will carry a thermal imager in their hands and then set it down when they need both of their hands for work. Once they lay it down, it’s very easy for it to get lost, forgotten or even damaged.
In the ever-changing world of fire service thermal imagers, it’s important to master the above basics and build a solid foundation for their safe and effective use with all the imagers your department employs. As departments purchase more imagers with improved technology and more features, it’s very important that firefighters receive additional training to address those changes. Unfortunately, some departments and firefighters have taken the approach that thermal imaging is as simple as turning it on, and if you can use one thermal imager, you can use any thermal imager. Although thermal imaging use does not have to be overly complicated, and there are many similarities among all thermal imagers, detailed, imager-specific training is required for optimal and safe use.
Mike Richardson is a 26-year military and fire service veteran, currently serving as a training officer for the St. Matthews Fire Department in Louisville, Ky. He graduated with honors from the Eastern Kentucky University Fire & Safety Program. He has instructed firefighters in more than 35 states and eight countries, and has served as an instructor for FDIC, Firehouse Expo and Fire-Rescue International. He also currently serves as an instructor for SAFE-IR.
Sidebar: NFPA Standard 1801—Better Late Than Never!
Unlike most other pieces of equipment in use by firefighters, thermal imagers have been produced and used without the guidance of a corresponding NFPA standard for more than 15 years. Fortunately, with the publication of the 2013 edition of NFPA1801: Standard on Thermal Imagers for the Fire Service, that will slowly but surely change. As imagers are produced that meet the new standard, the fire service will finally start to see the benefits that an NFPA standard can bring about. Two areas to highlight include minimum performance standards and standardized operations.
Minimum performance standards. As with other equipment such as PASS devices, a thermal imager will now have to meet a minimum performance standard for criteria, such as heat, water and impact resistance, as well as produce a minimum level of image quality for critical applications, such as victim identification and hazard recognition. These standards will be reinforced through testing and verification by an independent third party.
Standardized operation. This will include a given set of operational criteria for both a “TI Basic” and a “TI Plus” operational mode. All imagers meeting the standard will have to automatically start in a “TI Basic” mode, which includes:
- Grayscale display, with white equaling hot and black equaling cold
- Power status indicator
- Internal temperature overheat indicator
- Imager status “On” indicator
This basic operational mode will ensure that a firefighter can turn on any compliant imager and have an understanding of how it’s operating and what they’re seeing.
The basic operational mode may also allow for the incorporation of additional features, such as display colorization of yellow, orange and red progressively and the associated temperature “kick-in” points displayed and temperature measurement. In the past these features could cause confusion with operators who do not fully understand their specific make/model of thermal imager. Additionally the standard calls for a TI Basic Plus operational mode to include all additional options/special features and functions that a user may want to customize their specific thermal imager with that are not included in TI Basic. The Basic Plus operational mode features require firefighters to take extra steps in the operational process to gain access to them. Untrained users in these features may simply depress the standardized Green On/Off button to revert the imager to the TI Basic operational mode.
Although the new NFPA 1801 standard is a move in the right direction, there are still issues that it does not cover and that the fire service will have to address. Those issues include:
- Existing thermal imagers—the thousands of imagers already in service will not be addressed by the standard. Attrition will eventually see the noncompliant imagers replaced over time, but until then, the fire service will simply have to deal with large variations that exist in imagers through proper training and maintenance programs.
- Thermal imaging training—the 1801 standard does not cover any aspect of thermal imaging training. It will still be up to individual departments and training agencies to determine the training that is needed to use an imager effectively and safely.
As with any new NFPA standard, 1801 will be a “work in progress” and will take a number of years to develop and fine-tune. Ultimately, when combined with a new corresponding training standard, it will ensure that the fire service has a robust and reliable thermal imager that can help firefighters perform effectively and safely.
As of the publication of this article, there have been no thermal imagers produced, tested and found to be compliant with the standard. However a number of fire service thermal imager manufacturers anticipate having compliant imagers in firefighters’ hands by late 2012.
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