Fugitive emissions, including excess emissions from poorly operating vented or combustion sources, are (by denition) unknown and must be detected before they can be quantied, reported, and mitigated. In contrast, properly operating vented and combustion sources are generally known to operators, and are typically estimated and reported to regulatory or voluntary programs. Most maintenance events are short, episodic, emission sources. Operators typically log the time and nature of the event and estimate emissions for reporting via a variety of engineering methods. A typical production operation in one basin may have hundreds of events per workweek.