A field study was conducted to evaluate the performance of three commercially available particulate matter (PM) continuous emission monitoring systems (CEMS) during 1999-2000 at the U.S. Department of Energy (DOE) Toxic Substance Control Act (TSCA) Incinerator located near Oak Ridge, Tennessee. The incinerator is permitted to treat mixed-waste, Resource Conservation Recovery Act (RCRA) hazardous and nonhazardous waste, and wastes containing polychlorinated biphenyls (PCB). The mixed-waste treated at the incinerator contains both low-level radioactive and hazardous chemical constituents. The air pollution control system of the incinerator utilizes Maximum Achievable Control Technology (MACT), which is comprised of a rapid quench, venturi scrubber, packed bed scrubber, and two ionizing wet scrubbers in series. The CEMS chosen for the demonstration were two beta-gauge devices and a light-scattering device. The performance of the CEMS was evaluated using the requirements in the Environmental Protection Agency (EPA) draft (11-3-98) Performance Specification 11 (PS11) and draft (11-3-98) Procedure 2. The various possible combinations of treating liquid, aqueous, and solid wastes simultaneously presented a challenge in establishing a single, acceptable correlation relationship for the individual CEMS. The flue gas of the incinerator was also continually at or near saturated moisture conditions, yet offering an additional challenge to the CEMS. The results of the EPA reference Method 5i stack tests for establishing the calibration .curves demonstrated that the beta-gauge monitors could meet PS11 criteria, and the light-scattering monitor could not meet PS11 criteria. Experience seemed to establish however, that more than one set of correlation tests might be necessary to determine the nature of the calibration curve