NIST Technical Note 1491 

Michelle K. Donnelly 

William D. Davis 

Michael J. Selepak 

Performance of 

Thermal Imaging Cameras 

In High Temperature Environments
NIST Technical Note 1491 

Performance of 

Thermal Imaging Cameras 

In High Temperature Environments

Michelle K. Donnelly 

William D. Davis 

Michael J. Selepak 

 Building and Fire Research Laboratory 

November 2007 

1 

National Institute of Standards and Technology 

 James M. Turner, Director 

U.S. Department of Commerce 

Carlos M. Gutierrez, Secretary 
2 

Certain commercial entities, equipment, or materials may be identified 

in this document in order to describe an experimental procedure or 

concept adequately. Such identification is not intended to imply 

recommendation or endorsement by the National Institute of Standards 

and Technology, nor is it intended to imply that the entities, materials, 

or equipment are necessarily the best available for the purpose. 

National Institute of Standards and Technology Technical Note 1491 

Natl. Inst. Stand. Technical Note 1491, 14 pages (November 2007) 

CODEN: NSPUE2 
Table of Contents 

ABSTRACT...................................................................................................1 

INTRODUCTION...........................................................................................2 

Table 1 Thermal Classes for Testing Electronic Equipment .......................2 

 Equipment and Testing Procedures...................................................................3 

Figure 1 Diagram of Fire Equipment Evaluator (FEE) ............................. 3 

Figure 2 Photograph of TIC target.......................................................4 

Figure 3 Photograph of the FEE..........................................................5 

RESULTS.....................................................................................................6 

Figure 4 Velocity measured in the FEE test section....................................6 

Figure 5 Temperature measurements at Thermal Class I, 100 °C .................7 

Figure 6 Temperature measurements at Thermal Class II, 160 °C ...............8 

Figure 7 Temperature measurements at Thermal Class III, 260 °C ...............8 

 Thermal Class I – 100 °C for 25 min..................................................................9 

 Thermal Class II – 160 °C for 15 min................................................................9

 Beyond Thermal Class II..............................................................................10 

Figure 8 Photograph of TIC 3 image darkening......................................11 

 Results Summary.......................................................................................12 

Table 2 Results Summary................................................................12 

 Discussion...........................................................................................13 

CONCLUSIONS............................................................................................13 

Future Directions...........................................................................................14 

REFERENCES.............................................................................................14 

ACKNOWLEDGEMENTS..............................................................................14
ABSTRACT

Thermal imaging cameras used by firefighters and other emergency responders must maintain 

acceptable image quality while operating in the severe conditions of a fire environment. 

Currently, there are no standard performance metrics for these cameras. This work investigates 

the impact of elevated temperatures on the operation of three different thermal imaging cameras. 

A heated air flow loop was used to provide the elevated thermal environment, and a variable 

temperature target served as a viewing object. Results of the testing are presented. 

1 
INTRODUCTION 

Firefighters working a building fire face a combination of severe environmental conditions, 

which include elevated temperatures, high humidity, thermal radiation, and smoke. Thermal 

Imaging Cameras (TICs) are often used by firefighters to identify hot spots or to do search and 

rescue operations. TICs are challenged to operate under the harsh conditions of the fire 

environment, which can impede the normal operation of electronic equipment. Performance 

standards need to be developed for TICs that are consistent with the fire environment 

experienced by firefighters. 

Currently, it is up to the manufacturers of TICs to set performance metrics and to test their 

equipment to ensure it meets these metrics. As of this writing, there are no universal 

performance metrics or standardized test methods for TICs. The National Fire Protection 

Association (NFPA) is in the process of developing performance standards; however, they are 

still in the planning stages. Researchers at the National Institute of Standards and Technology 

(NIST) are currently developing performance evaluation techniques to characterize TIC image 

output in ambient operating conditions (Amon et al., 2006; Amon and Hamins, 2006; Amon et 

al., 2004). 

The effect of elevated temperatures on the operation of TICs was examined as part of an ongoing 

effort by NIST to characterize the effects of building fire environments on electronic equipment. 

During previous work, (Donnelly et al., 2006) the expected conditions encountered by 

firefighters and the various classifications of these conditions were investigated. Through 

research and experimental testing, thermal classes for electronic equipment exposures were 

developed by NIST. These thermal classes were used as guidelines for testing TICs at elevated 

temperatures. Table 1 shows the sustained air temperature and corresponding exposure time 

used to test the equipment for these thermal classes. Operation at the preceding thermal class 

was required before testing at a higher class. 

The thermal response of a small sample of TICs was evaluated to determine the feasibility of 

developing thermal standards for the TICs. The goal was to investigate operational response to 

elevated temperatures, test TIC image targets, and evaluate the testing equipment, in order to 

provide recommendations for TIC thermal standards. The purpose of these tests was not to rank 

the performance of cameras by different manufacturers. Only one sample of each type of camera 

was used for testing. 

 

Table 1 Thermal Classes for Testing Electronic Equipment 

Thermal Class Exposure 

Time (min) 

Sustained Air 

 Temperature (°C)/(°F) 

Additional Temperature 

Requirements 

I 25 100/212 none 

II 15 160/320 Thermal Class I 

III 5 260/500 Thermal Classes I and II 

2 
Equipment and Testing Procedures 

The Fire Equipment Evaluator (FEE) provided the thermal environment for testing the TICs. 

The FEE is a heated, recirculating air flow loop, driven by a high temperature blower, which 

produces a controlled and repeatable thermal environment for testing. A diagram of the FEE is 

shown in Figure 1. The air flows through the stainless steel loop at velocities from 0.5 m/s to 

2.0 m/s, with temperatures up to 300 oC. The FEE measures 220 cm long by 174 cm high and 

contains a testing section that is 91 cm long, with a cross section area of 38 cm by 38 cm. 

Thermocouples throughout the loop provide temperature measurements at various locations. A 

bidirectional probe is used for the velocity measurements. Further details concerning the 

components and operation of the FEE can be found in Donnelly et al., 2006. 

174 cm

220 cm 

Door to 

Testing Section 

Heater

Blower 

Honeycomb 

Honeycomb

Flow 

Window 

Hot Plate 

With Target 

CCD camera 

 Figure 1 Diagram of Fire Equipment Evaluator (FEE)

During testing, each TIC was placed in the testing section of the FEE, which was accessed 

through a door on the side of the FEE as indicated in Figure 1. The TIC was positioned so that 

its display screen faced upwards toward a window on top of the FEE. To monitor and collect 

images of the TIC display screen, a CCD camera was placed outside the FEE, above the window 

3 
and was aligned to view the TIC display screen. The CCD camera output signal was relayed to a 

PC where it could be continuously monitored, and still images could be saved. 

To evaluate the TIC displays, a variable temperature target was constructed. The target was 

made using 2.54 cm diameter Bakelite rods spaced 2.54 cm apart in a fixed vertical pattern. The 

rods were supported 0.3 cm above a hot plate with an area measuring 23 cm by 23 cm. The 

Bakelite rods and the surface of the hotplate were both painted with an optical black coating with 

an average emissivity of 0.94. The hot plate had an adjustable temperature range from ambient 

to 100 °C. When the plate was heated, the result was a temperature bar target with alternating 

areas of lower and higher temperatures when viewed from above, formed by the pattern of the 

Bakelite rods above the hot plate. Thermocouples measured the surface temperatures of the rods 

and the hotplate. For all of the elevated temperature tests, the hotplate was set to a temperature 

of 30 °C ± 3 °C. This tested the TICs in the high sensitivity mode, distinguishing a temperature 

difference of approximately 10 °C between the temperature of the hot plate and the temperature 

of the bakelite rods. Figure 2 is an infrared picture of the target, as viewed by a TIC. The light 

areas indicate the higher temperatures. 

Figure 2 Photograph of TIC target as viewed by a TIC. 

4 
The TIC temperature target was placed below the testing section of the FEE, at a distance of 

56.5 cm from the TIC lens. A 5 cm diameter hole was cut into the bottom of the FEE testing 

section, and was left open and uncovered, so that the TIC had an unobstructed line of site to the 

target. Flow evaluation tests verified that the viewing hole had a negligible effect on the TIC 

temperatures and flow patterns in the testing section. Figure 3 shows a photograph of the FEE 

setup, with the CCD camera above the testing section and the temperature target located below. 

The door to the FEE testing section is open in the photograph. 

Figure 3 Photograph of the FEE, set up for TIC testing. 

For thermal evaluation tests, a TIC was placed in the center of the testing section while the FEE 

was at ambient temperature. Ambient temperatures for these tests ranged from 20 °C to 24 °C. 

The TIC was positioned above the viewing hole, with an image of the target centered on its 

screen. Then the CCD camera was aligned and focused on the TIC image screen. At the 

beginning of each test, while the TIC and the test tunnel were at ambient temperature, initial TIC 

screen images were saved as baseline images. Next, the heater was activated, and the TIC was 

subjected to a heat-up time, which varied for each thermal class, but was repeatable for all tests 

5 
conducted at the same temperature. The heat-up time was 330 s for the 100 °C, Class I tests, 

400 s for the 160 °C, Class II tests, and 700 s for the Class III, 260 °C test. Once the airflow 

inside the FEE reached the desired temperature, it was maintained at this temperature for the 

corresponding exposure time specified in Table 1. 

The TIC image display was also monitored during the cool down period following each elevated 

temperature test. Cameras were allowed to cool completely, reaching ambient room temperature 

between tests. Batteries were fully charged between tests, and the TICs were placed inside the 

FEE with a full battery charge at the start of each thermal test. Some battery usage occurred 

during the camera alignment prior to heating, which typically took approximately 10 minutes. 

RESULTS 

Three TICs, each from a different manufacturer, were exposed to elevated temperatures, using 

the thermal classes listed in Table 1 as the guidelines for camera exposures. For all tests, the 

blower motor speed was set at a rotation of 20 Hz. This resulted in an air flow velocity through 

the testing section of 0.83 m/s ± 0.05 m/s for the Class I and Class II temperatures, and 0.93 m/s 

± 0.05 m/s at the Class III temperature, and is comparable to a slow walking speed. A plot of the 

measured velocity at the three different temperatures is shown in Figure 4. The viewing screen 

of each camera was continuously monitored throughout the test, and stills from the CCD camera 

were periodically saved. In addition, objects were moved in and out of the TIC field of view, 

above the target, to ensure that the camera was working and that the screen did not become 

frozen on an image. 

0

0.2

0.4

0.6

0.8

1

1.2

0 250 500 750 1000 1250 1500

Class I, 100 oC

Class II, 160 oC

Class III, 260 oC

Velocity (m/s)

Time (s)

Figure 4 Velocity measured in the FEE test section at three different temperatures. 

6 
The temperatures inside the tunnel were measured at different locations during the testing. 

Thermocouples placed in a row vertically measured the temperature at various heights at the 

center of the testing section, approximately 3 cm upstream of the camera. Two thermocouples 

were also attached to each TIC. One thermocouple measured the temperature of the image 

viewing screen, which faced the top of the tunnel. A second thermocouple was attached to the 

body of the camera, on the side facing the FEE door, to monitor the outer temperature of the 

camera body. Figure 5, Figure 6, and Figure 7 show temperature measurements inside the FEE 

for Thermal Class I, Thermal Class II, and Thermal Class III conditions, respectively. Time zero 

indicates when the heaters are turned on, and the start time and end time for the timed 

temperature exposures is indicated. Figure 5 shows that the temperatures of the TIC body and 

the screen remained more than 10 °C cooler than the air temperature inside the FEE during the 

100 °C tests. Temperatures of the TIC body and the screen were more than 30 °C cooler than the 

air during the 160 °C tests, as shown in Figure 6. For the Class III, 260 °C test, the FEE air 

temperature was approximately 90 °C warmer than the TIC screen temperature, as shown in 

Figure 7. During the Class III test, the thermocouple located on the TIC body stopped working 

approximately 400 s into the test, so no temperature was recorded at that location beyond 400 s. 

20

40

60

80

100

120

0 500 1000 1500 2000 2500

8 cm above

Centerline

8 cm below

TIC screen

TIC body

Temperature (oC)

Time (s)

start end

Figure 5 Temperature measurements at Thermal Class I, 100 °C. 

7 
0

25

50

75

100

125

150

175

200

0 200 400 600 800 1000 1200 1400

8 cm above

Centerline

8 cm below

TIC screen

TIC body

Temperature (oC)

Time (s)

start end

Figure 6 Temperature measurements at Thermal Class II, 160 °C. 

0

50

100

150

200

250

300

0 200 400 600 800 1000 1200

8 cm above

Centerline

8 cm below

TIC screen

TIC body

Temperature (oC)

Time (s)

start end

Figure 7 Temperature measurements at Thermal Class III, 260 °C. 

8 
Thermal Class I – 100 °C for 25 min 

Camera 1 worked properly under the Class I conditions of exposure to an air temperature of 

100 °C for 25 min, following the 330 s heat up period. There were no problems with the 

operation or visible degradation of the screen image. The camera continued to work throughout 

the heat soak and cool down. Inspection of the camera after the test showed no melting, warping, 

or damage of any kind to the camera or battery. 

Camera 2 worked throughout the Class I conditions of 25 min at 100 °C without visible changes 

to the image on the display. The camera display remained unchanged during cool down and 

continued to function after the test. The camera was inspected after cool down, and showed no 

signs of damage to any parts of the camera or battery. There was one anomaly during this test. 

The battery indicator dropped quickly, moved back up to nearly full, then dropped quickly again, 

and repeated this throughout the heating. The up and down inconsistency of the battery indicator 

had no apparent impact on the camera operation, and the image was not affected. To determine 

if the abnormal response of the battery indicator was a result of the camera being heated, or a 

defect in the camera itself, the camera was allowed to cool overnight, and was then operated at 

ambient temperature for one hour. During this time the battery indicator was observed, and no 

anomalies were witnessed while operating the camera at ambient temperature. 

Camera 3 worked properly throughout the Class I conditions of 100 °C temperatures for 25 min. 

There were no degradations of the picture during the test. A “high temperature” warning 

appeared on the camera screen near the end of the thermal exposure, at 22.75 min, but there was 

no observable change in the camera image as a result of the warning. Inspection of the camera 

after the test showed no melting, warping or any other observable damage to any parts of the 

camera. The camera was fully functional after the Class I test. 

Thermal Class II – 160 °C for 15 min 

Camera 1 functioned properly throughout the Thermal Class II conditions of exposure to 160 °C 

for 15 min, following the standard 400 s heat up period. The camera image remained clear, and 

there were no signs of image degrading during the heat exposure or cool down. After the test, 

the camera was inspected. There was no observable damage to the camera or battery. Camera 

operation was normal following this test. 

 

Camera 2 only worked for the first few minutes at the Class II temperature of 160 °C. At a time 

of 168 s into the thermal exposure, the image suddenly disappeared, and the screen was filled 

with static. The occurrence was abrupt, and there was no blurring or distorting of the image and 

no warning from the camera; the screen simply went from showing a clear image to showing 

only static. The battery indicator was still functioning and indicating a mostly full battery. Other 

than the picture no longer working, there was no noticeable damage to any other parts of the 

camera. Camera 2 was allowed to cool overnight, and the battery was replaced; however, 

operation of the camera was not restored. 

Camera 3 functioned normally during the 15 min exposure at the Class II temperature of 160 °C; 

however, all camera operations failed during the cool down period. Throughout the heated 

period, the camera image remained clear with no degradation. Near the end of the thermal 

9 
exposure, after 12.75 min, the “high temperature” warning appeared on the camera screen. 

There was no degradation of the image, and the camera continued to operate properly and deliver 

a clear picture for the last few minutes of the Class II test. The camera was then allowed to cool, 

and approximately 5 min into the cool down period, the camera stopped working. As with 

camera 2, there was no degrading of the image; the display just abruptly went dark. During the 

inspection of the camera after the test, it was noted that the battery remained very warm, while 

the rest of the camera was at room temperature. The camera was allowed to cool for three days. 

A new battery was supplied to the camera, but it did not regain operation following this test. 

Beyond Thermal Class II 

Before testing at the Thermal Class III conditions, an intermediate test was performed on 

Camera 1 by subjecting it to a 5 min thermal exposure at 210 °C. The camera functioned 

perfectly throughout this test. The image on the camera display was unchanged throughout the 

test and the cool down. Following cool down, the camera was inspected, and there was no 

observable melting, deformation, or any damage to any parts of the camera, except for the 

battery. The casing of the battery had melted slightly and had become warped. Inspection of the 

insides of the battery housing area showed no internal damage, including no damage to any of 

the exposed electronic components in this area. A new battery was supplied to the camera and 

the camera operated properly with this battery. 

Camera 1 was then tested at the Thermal Class III condition of 260 °C exposure for 5 min. This 

camera survived the 5 min exposure with no changes in the display and no degradation of the 

picture; however, it failed immediately afterwards during the cool down. Approximately 45 s 

into the cool down, the top edges of the screen began to darken. The darkening of the screen 

continued over the next 120 s, working from the edges to the interior until the entire image was 

gone. Figure 8 shows a picture taken 80 s into the cool down, with darkening of the screen 

visible in the upper right hand corner (compare with Figure 2). After cool down, an inspection 

of the camera revealed that the casing of the battery had melted and deformed. Other than the 

warping of the battery case, there was no other observable melting, deformation, or damage of 

any kind to any other parts of the camera. The battery housing area was inspected and showed 

no internal damage. A new, fully charged battery was then supplied to the camera; however, 

camera operation did not recover. 

10 
Figure 8 Photograph showing the screen of TIC 3 darkening just before failure. 

11 
Results Summary 

A summary of the results of this preliminary testing is shown in Table 2. All three cameras 

tested were able to withstand the exposure to Thermal Class I conditions, with no observable 

damage and no impairment of camera operation. After the Thermal Class II exposure; however, 

only one of the three cameras was functional. One camera stopped working after a few minutes 

at the Class II temperature, and another camera failed during the cool down period. The third 

camera survived the 5 min at the Class III temperature of 260 °C, but stopped working shortly 

afterwards during cool down. In all cases, once the camera had stopped working, the failure was 

permanent. Operation was not restored after the camera had cooled and the battery was replaced. 

 

 

Table 2 Results Summary 

Camera Temperature Time Image during soak Cool Down Observations 

Camera 1 100 °C 25 min Clear Image Operates properly No damage 

Camera 2 100 °C 25 min Clear Image 

(battery indicator 

operated erratically 

but the image 

remained good) 

Operates properly. No damage 

Camera 3 100 °C 25 min Clear Image Operates properly No damage 

Camera 1 160 °C 15 min Clear Image Operates properly No damage 

Camera 2 160 °C 2 min 

48 s 

Failure - no image 

after time indicated 

Camera has failed No operation 

with new 

battery 

Camera 3 160 °C 15 min Clear Image Camera fails during 

cooling 

No operation 

with new 

battery 

Camera 1 210 °C 5 min Clear Image Operates properly Battery warped, 

Operates 

properly with 

new battery 

Camera 1 260 °C 5 min Clear Image Camera fails during 

cooling 

Battery warped, 

No operation 

with new 

battery 

12 
Discussion 

The three TICs tested, though similar in description, exhibited different abilities to withstand 

elevated temperatures. These tests showed that at least some of the TICs currently on the market 

are susceptible to failure at thermal conditions experienced in firefighting. The lack of standard 

performance metrics has resulted in a huge difference in the temperature tolerances of the 

cameras. The outer casings withstood the high temperature assaults with no warping or other 

damage; however, heat transfer to the inner workings resulted in eventual failure of TIC 

operations. 

The inclusion of a “high temperature” warning that was present in one of the cameras is a useful 

feature since it was the only indication of impending camera failure for that particular camera. 

The other cameras had no warning mechanism for failure due to high temperatures. 

Prior to this testing, we did not have any knowledge of the camera behavior at elevated 

temperatures. The temperature target was prepared with the expectation that the TIC display 

screen images would experience some type of degradation or loss of sensitivity, possibly 

followed by camera failure. The target was designed to allow for evaluation of the images and 

any picture degradation to be quantified. When the tests were conducted, it was found that the 

display screen images remained clear up to the point of complete failure. Any possible image 

degradation during these tests was not visible to the naked eye, and was deemed negligible for 

the purposes of this evaluation. TIC 1 did experience darkening around the edges before the 

display stopped working. 

Both Thermal Class I and Thermal Class II represent conditions where search and rescue, and 

identification of hot spots would likely be conducted using TICs. The fact that one of the three 

TICs tested was capable of surviving Thermal Class II conditions suggests that it is technically 

feasible to consider Thermal Class II conditions when developing a standard for TICs. 

CONCLUSIONS 

These preliminary tests on a limited number of TICs revealed some basic findings about camera 

operation at elevated temperatures. 

1. All TICs tested operated properly throughout the Thermal Class I temperature exposure. 

2. Only one of the three cameras continued to function after Thermal Class II exposure. 

3. The failure mode for each of the TICs was due to loss of the display screen image. In 

two cases the display image failure was abrupt, and in the third case the screen slowly 

darkened over the course of about two minutes. 

4. For these three cameras, operational failure was permanent. Once the cameras stopped 

working, operation could not recover by cooling the camera or replacing the battery. 

5. There was no observable melting, warping or damage to the outer casings of the TICs at 

the conditions where the inner components were damaged. 

6. The thermal classes developed in an earlier paper worked well in quantifying the 

performance of the three TICs and could be considered as a basis for developing 

industry-wide standards for these devices. 

13 
Future Directions

For this set of experiments, heat was the only component of the fire environment that was 

investigated. Other components of the fire environment, such as smoke, chemicals or water 

vapor can impact the operation of electronics. If the instrument casings or seals of the TICs are 

compromised due to heat, then it may be possible for smoke, chemicals or water vapor to 

penetrate and interfere with the camera operation. These preliminary results showed no 

observable breaches in the outer casings, but further testing is needed to verify that the cameras 

can survive these additional insults. 

REFERENCES 

Amon, F., Benetis, V., Kim, J., and Hamins, A., “Development of a performance evaluation 

facility for fire fighting thermal imagers,” Proceedings of SPIE, Vol. 5407, No. 35, 2004. 

Amon, F., and Hamins, A., “First responder thermal imaging cameras: development of

performance metrics and test methods,” Proceedings of SPIE, Vol. 6207, Infrared Imaging 

Systems: Design, Analysis, Modeling, and Testing XVII, Gerald C. Holst, Editor, 62070S (May. 

16, 2006), 2006. 

Amon, F., Hamins, A., and Rowe, J., “First responder thermal imaging cameras: establishment of

representative performance testing conditons,” Proceedings of SPIE, Vol. 6205, 62050Y, 2006. 

Donnelly, M. K., Davis, W. D., Lawson, J. R., and Selepak, M. S., “Thermal Environment for 

Electronic Equipment used by First Responders,” National Institute of Standards and Technology, 

Gaithersburg, MD, NIST Technical Note 1474; January 2006. 

ACKNOWLEDGEMENTS 

This work was sponsored by the Department of Homeland Security (DHS) via the NIST Office 

of Law Enforcement Standards (OLES) to advance the development of Standards for Electronic 

Equipment used by Emergency Responders. 

The authors would like thank Dr. Francine Amon for her helpful discussions and input on this 

work. The authors would also like to thank Joshua Dinaburg for his assistance with the CCD 

camera operations. 

14