Chemical releases and worker exposures associated with the filtration of an industrial wastewater sludge were characterized. The filter was a recessed chamber filter press with an open filtrate discharge system. Chemical releases and worker exposures for a selected chemical were measured over four operational cycles and various aspects of the filtration operation believed to influence the measurement values were documented. Ventilation patterns around the filter press were monitored. The worker's time-weighted average exposures to total copper (low vapor pressure, highly insoluble form) during the 113-minute operational cycle ranged from 3.1 to 25 micro g/cu m. To sludge feed and filter cake copper concentrations were approximately 0.1 and 1.0 weight percent. A noticeable difference in worker techniques was observed which may account for the large range of inhalation exposures during the cake removal stage. During this stage, the inhalation exposures ranged from 11 micro g/cu m to 130 micro g/cu m. The manual removal of filter cake comprised only 15% of the time in an average filtration cycle, but produced 72% of the worker's inhalation exposure.