It sees what an eye can’t
Thermal imaging cameras are an excellent tool for intrusion detection in zero light conditions, or in bad weather. Thermal cameras see what conventional cameras cannot see, because they don’t need any light. All objects emit a heat signature over the absolute zero conditions (–273.15°C or –459.67°F) and thermal cameras see their heat signature.
Thermal cameras can detect targets miles away, or up close. The best use for thermal cameras is for perimeter detection, and as a component working together with day/night IR cameras for identification.
The images below shows the contrast in detection levels between a conventional day/night IR camera (top row images) and a thermal camera (bottom row images). Both, top and bottom images are of the same scenes, only captured by a different camera (Conventional v. Thermal):