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. The measurement of particle mass rather than other particle parameters is emphasized. Although the report emphasizes permanently-installed effluent monitoring systems, much of the information is also applicable to portable and research instruments. Detailed discussions of particle sensing techniques as applied to emissions monitoring are presented. Each discussion analyzes possible problems and their solutions, in using the technique for emission monitoring, and includes an analysis of what particulate parameter the technique sees, how closely the measurement correlates with particulate mass, inherent measurement errors, practical design problems and possible solutions, the potential sensitivity and response of each technique, the complexity of the potential instrument, the present state of development of the technique, and recommendations for further development. Each discussion includes a complete bibliography. A separate chapter describes typical conditions found in large fossil-fuel effluent gases in detail. Another separate chapter summarizes many of the problems encountered in the design of sampling probes required by most of the particle sensing techniques.