Now compare the visible image with one taken in the thermal IR (infrared) range. The location of the fire (bright patches in the image) can actually be pinpointed with accuracy using this last type of light. The thermal IR (unlike the visible frequencies) is relatively unaffected by the smoke from the fire. This is why it can be so effectively used to remotely-sense the hottest regions in the forest fire. Fire fighting equipment can then be rapidly sent to the most critical areas.
Image supplied courtesy of Daedalus Enterprises, Inc., Ann Arbor, MI