Abstract: An apparatus for detecting the presence of carryover particles in an upper region of a furnace, such as a smelt bed boiler, includes plural spaced apart detectors. These detectors monitor discrete portions of the interior of the furnace for the purpose of detecting carryover particles in such monitored portions. Signals indicative of the carryover particles are processed to obtain a count of the carryover particles. The carryover particle count may then be displayed. For example, the signals from all of the detectors may be averaged with trends and overall changes in count rates then displayed. In addition, the counts from the individual detectors may also be displayed to assist an operator in locating the source of excessive carryover particles in the furnace. An image sensor, such as a charged coupled device (CCD) detector, may be used to provide a visual display of detected carryover particles.