The research described in this paper has emerged from a program designed to develop techniques for detecting and measuring atmospheric dispersion of effuent materials. Several diffusion experiments have recently been completed using sulfur hexafluoride (SF6) to trace gases, especially those emitted from tall stacks. Airborne and ground level concentration measurements using specially designed gas chromatographs were made. The results extracted from the experiments illustrate the usefulness of this method in detecting low-level concentrations many kilometers downwind from given sources.