Originally developed for military use during the Korean War, thermal camera lenses have migrated into other fields and have found many uses. Firefighters use them to see through smoke, find people and localize hotspots of fires. Law enforcement uses the technology to manage surveillance activities, locate and apprehend suspects, investigate crime scenes and conduct search and rescue operations. Power line maintenance technicians locate overheating joints and parts to eliminate potential failures. Where thermal insulation becomes faulty, building construction technicians can see heat leaks to improve the efficiencies of cooling or heating. Physiological activities, such as fever, in human beings and other warm-blooded animals can also be monitored with thermographic imaging. They are also common tools used by home inspectors.
Thermal camera lenses can be purchased with the bare minimum of features that only read the temperature of the fixed center crosshairs on the display or with multiple features that allow the user to select multiple moveable crosshairs and draw comparisons between them to show the high, low and average temperatures on the display. Thermal camera lenses have user-selectable multiple color palettes, such as black/white, iron or rainbow. The iron palette is most commonly used by home inspectors. The black/white palette helps identify details on an image, and the rainbow palette has the best thermal sensitivity for displaying the differences in temperature. See sample images below of some color palettes.