Tube metal temperatures are critical to furnace operations. When operating a furnace close to the maximum allowable tube metal temperature, changes of less than 200° F can dramatically reduce tube life on tubes rated for 100,000 hours to only a few hundred hours. Operations personnel rely on thermocouples as the primary tool to provide the temperature data necessary for making critical process decisions. However, the data that thermocouples provide is extremely limited. The primary limitation is the fact that thermocouples only supply data for a specific point on the tube. Most distillation furnaces only have 1 to 3 thermocouples per pass. In service applications that involve internal fouling such as distillation, it is not unusual to see tube metal temperature variations of 200° F or more in areas of fouling. This paper describes how an infrared inspection program can identify potentially catastrophic problems in distillation furnaces that could be easily missed when relying on thermocouple data or visual inspection.