As noted earlier, a change in operating state of the facility may change emissions signicantly. The primary factors driving emissions at a facility are the online status of compressor or processing units, the load on these units, and changes to process settings. Emissions at the facility may also be inuenced, typically to a lesser degree, by other process equipment, such as gas upgrading equipment. Prior studies have indicated that emissions driven directly by the operating state of compressor units often dominate overall emissions from midstream facilities. 9,10 Therefore, compressor operating state provides a useful surrogate for the facility state at midstream facilities, and are, of course correlated with the throughput of compressor stations.