Thermal Imaging – why is today’s technology better

Jan 28, 2021


When Infrared Technology (Thermal Imaging) was first introduced into the Fire Services in the late 90s, the few manufactures that jumped on board did not have the vision then as to what the technology would be like today. The demand and the NFPA have forced manufacturers to step up their “A” game to stay competitive with the technology changes.

What’s the definition of the best image quality in the fire service?

When comparing thermal imagers today to 5 to 10 years ago, there has been a vast improvement in technologies from size, weight, cost, battery performance, refresh rate, resolution, and image quality. By far my preference for the best image quality is based on the following criteria: screen size, refresh rate, and resolution (i.e. 3.5”/88.9 mm screen size, 60Hz refresh rate, 320×240 resolution with clear imagery). Anything less, in my opinion, will still do the job but not as fast or efficient.

How do we judge the image quality in the specification? Resolution? Update rate? Dynamic range?

When a fire department decides to purchase equipment, there generally is a committee of members that can range from firefighters, training and administration divisions, and purchasing. All have a specific function or role to perform as a member of the committee. Purchasing is going to look at the cost of the project, the administration will review the requirements, and the training and firefighter members are going to look at the technology and what equipment is available. Manufacturers are generally asked to provide specifications and comparisons. Based on this information, recommendations to purchase equipment usually follow with a winner selected.

You may be asking, is that all that happens? I sure hope not! All thermal imagers are not created equal by today’s standards. The fire department should arrange a live-fire testing scenario to ensure that the TI performs to the committee’s expectations so the department doesn’t make a purchase it might regret later because the TI didn’t perform to expectations. Let me give you an example. Let’s talk about Update or Refresh Rate as I like to call it. This is basically the shutter speed that refreshes the imager’s internal core which can range from speeds of 9Hz, 15Hz, 30Hz, and 60Hz. The faster the refresh rate, the less critical information is missed. So, conduct tests under live fire conditions and have the imagers lined up next to each other for visual comparisons. Imagers with a 9Hz to 15Hz refresh rate will see about a 2+ second delay as opposed to the 60Hz imager which will shutter in a very quick split second.

Resolution in today’s thermal imagers ranges from 320×240 resolution. There are some 240x180s but the original 160×120 has been long surpassed.


photo courtesy of Bullard – images here in the low gain state 

Here are some helpful ideas for conducting side by side thermal imager evaluations. (1) Distance measurement by placing personnel every 25ft/7.62 meters up to 200 ft/60.96 meters to see what kind of range you get. (2) Hazmat testing for liquid levels in containers or escaping gas from a propane cylinder. (3) Conduct a live fire and look for flow path and thermal layering, high heat colorization, and victim location. (4) Evaluate an overhaul scenario by taking a metal pail that contains heated charcoal BBQ briquets and bury it in the dirt.

Dynamic Range can be confusing as a majority of TI manufactures have 2 gain states which are High and Low, and some have 3 gain states of High, Medium, and Low. With this thought process, more would be better right? It’s not. By having more, we lose definition in our imagery which can lead to confusion about missing our means of egress or unable to locate a missing victim during a critical search.

The above photo shows an imager on the left side in a low gain state and the imager on the right side shows a low gain state as indicated by the symbology in the green box with a green triangle in the upper left corner which will appear at 300 deg F/148 deg C. The imager on the right side actually has 3 gain states…so, now do you think that more is better? What can’t you see?

When an imager shifts gain states it does it to protect the core from overheating and dials down the amount of heat that enters to maintain image quality.

Temperature measurement also falls under the Dynamic Range category as a majority of thermal imagers reach temps of up to 1200 deg F/600 deg C while some other manufactures exceed that. Anything more than 1200 deg F.260 deg C, in my opinion, would be a moot point because what you have to consider is what temperature range can your Personal Protective Equipment (PPE) handle. Fire Helmets being the highest part of a firefighters body are rated for 500 deg F/260 deg C while Nomex Hoods are rated for 572 deg F/300 deg C and SCBA facepieces range from 290-446 deg F/143-230 deg C. Bunker gear being brand new out of the box will provide up to 17.5 seconds of protection if you are caught in a flashover. So again, I ask, is more Dynamic Range better?

High Gain vs Low Gain – this imager has only 2 gain states.

What’s the difference between the fire service and the general industry when using a thermal imaging camera regarding the image quality?

Today’s thermal imagers have pretty much the best image quality that manufacturers can produce. After saying that, can I use an industrial thermal imager for firefighting purposes? Sure you can but for exterior events only such as size-up and missing persons, etc. The difference between the 2 types of imagers is how they are manufactured. Fire service TIs go through a series of stringent testing especially if they are NFPA 1801 compliant. Basic testing includes insertion into an oven at 500 deg F/260 deg C for 5 minutes for a heat test, 6ft/1.83 meter drops for durability, and submersion of 3ft/0.91 meters underwater for 30 minutes for IP67 waterproof testing. I am pretty sure none of the imagers manufactured for commercial purposes would stand up to the rigors of firefighting, so think before you purchase one!


Left side older technology – right side newer image enhanced technology.

Another point that I would like to make is about the in-screen colorization. Fire service thermal imagers start in the basic mode which shows white, black, and grey scale indicating hot objects are white, cold objects are black and everything in between are shades of grey. Imagers will produce a high heat colorization consisting of yellow, orange, and red as these colors also meet the NFPA standard. Industrial or commercial grade thermal imagers have many different color pallets depending on their purpose, therefore would be too confusing for Advanced Fire Fighting applications.

Image quality is key in order for the end user to be efficient in their firefighting duties.
Image quality is key in order for the end-user to be efficient in their firefighting duties.

How does the best image quality help firefighters on image interpretation?

Image quality is key for the end-user to be efficient in his/her firefighting duties. By being able to quickly scan down the hallway of a smoke-filled building allowing you to follow the flow path directly to the seat of the fire, makes for quicker extinguishment and therefore creating less property damage. With the ability to clearly see the information on the display screen of the TI, firefighters are quickly able to find victims that may be trapped within the structure and remove them to safety while continuing to monitor the conditions for their safety.

This photo above shows the difference from the same TI manufacturer between old versus new technology as a vast improvement. So, is today’s technology better than in the early 90s? It sure is, but wait for tomorrow’s technology as changes in the thermal imaging market are not going to end today!

Until next time stay safe and train often.


This article was published in Gulf Fire Magazine in January issue 2021.