Abstract: A three-part seal comprising an inboard, an intermediate and an outboard seal and defining two chambers, a mixing chamber between the inboard seal and the intermediate seal and a buffer chamber between the intermediate seal and the outboard seal, provides the capability of zero emissions of a process fluid under pressure in a housing. The process fluid may comprise a toxic or otherwise environmentally hazardous process fluid. A radial bore provides fluid communication between the buffer chamber and a buffer fluid reservoir, for example, a source of nitrogen gas, which is maintained at a pressure, preferably about five to eight psi, over the fluid pressure in the mixing chamber.