INTRODUCTION: Once a particular field or plant was selected as a site@ certain wells@ systems@ and subsystems were chosen for 100% screening and inventory. An important consideration in the determination of these internal boundaries was to include all stages of production@ from the wellhead@ to the sales point or LACT (lease automatic custody transfer). For example@ a given site might include a tank battery with all of its associated wells@ a compressor plant@ all processes in a treatment facility@ and the shipping system. In some cases where a large system consisted of several parallel subsystems with identical functions @ not all of the subsystems were tested. This was usually the case at a compressor plant where typically several of each type of compressor would be screened.