Thermal imaging cameras are a piece of kit that engineers use to find hidden leaks in places such as hot water pipes under floorboards, concrete and behind walls.
These cameras can be used to see and measure how much thermal energy is emitting from an object. Infrared inspection camera can also pick up on hidden water leaks and where it is originating from, not just that but moisture can also be detected in hard to reach places that cannot be picked up with a moisture meter.
Thermal imaging cameras pick up on light as heat and show this as an image. They detect the temperature of the first object in its line of sight, if you point the camera at a wall or solid surface the heat will get registered as being radiated outwards by that surface.