In all sectors, methane emissions are classied into three categories. Fugitive emissions refer to unplanned emissions, typically from leaks, abnormal process conditions, or degradation of operational components. Vented emissions refer to the planned release of uncombusted gas from maintenance operations (e.g. depressurization of equipment (blowdowns), well liquid unloadings, etc.) or the non-combustion use of pressurized gas in process control (e.g. gas-driven pneumatic controllers and pumps). Combustion emissions, or `combustion slip,' refers to unburned fuel gas in the exhaust from combustion processes, such as gas-fueled engines or turbines, heaters, ares, and thermal oxidizers.