All known sensing techniques available for application to automatic, continuous measurement of the rate of particulate mass emissions from large fossil-fuel combustion facilities are discussed. Emphasis is on the measurement of particle mass rather than other particle parameters, and emissions downstream rather than upstream of any control equipment. Although sensors for permanently-installed effluent monitoring systems are emphasized, much of the information is also applicable to portable and research instruments. Brief surveys are presented of all known particle sensing techniques. A brief discussion of the principle of operation is followed by a list of inherent and practical strengths and weaknesses of each technique. A list of commercial manufacturers of related equipment and a list of 1,352 references helps the reader who needs more information on a specific technique. Recommendations for further development outline areas of needed improvement for techniques which offer some promise for stack monitoring. The introduction includes general comments which apply to all sensing techniques, and ranks all techniques in order of present apparent potential. A separate chapter summarizes typical conditions found in large fossil-fuel effluent gases and sets the necessary specifications for a particulate monitoring instrument which operates in an effluent gas atmosphere.