At SERVPRO we use infrared cameras to locate areas that otherwise could appear dry. These cameras allow us to "see" and "measure" thermal energy emitted from an object. Thermal, or infrared energy is light that is not visible because its wavelength is too long to be detected by the eye; it's the part of the electromagnetic spectrum that we perceive as heat. Unlike visible light, in the infrared world, everything with a temperature above absolute zero emits heat. Even very cold objects, like ice cubes, emit infrared.
This image is a great example of how our infrared cameras work. As you can see on the left, everything looks normal. However when looking through an infrared camera you can visibly see that water has absorbed into the drywall. Since water is cooler than the surrounding drywall and emits less infrared energy we can see how far the water damage has absorbed into the material, giving us the ability to dry all of the affected areas; not just what appears wet.