The objective of this program was to develop cost-effective methods of controlling mercury vapor in a processing mill furnace room with particular emphasis on the McDermitt mercury mill in Nevada. Process, environmental, and operating data were collected at McDermitt and a preliminary evaluation of control systems was performed. Efforts were focused on the furnace, which is the primary mercury emission source, and furnace positive pressure or "blowback," which is the cause of the greatest furnace emissions. Cost-effective conceptual design alternatives were prepared that addressed the identified emissions problems, particularly furnace blowback. Two designs were selected and detailed design drawings and cost estimates were prepared. The first design agglomerates the filter cake upstream of a belt conveyor, which replaces the existing screw conveyor. The second design dries the filter cake to 5 percent moisture before conveyance on the belt conveyor. Both designs are expected to reduce mercury vapor concentrations by more than 500 ug/m3 in the furnace building and approximately 160 ug/m3 in the concentrator building during furnace operations.