A duration estimate is required for all emissions exceeding the 100 kg/hr reporting threshold so that a total mass of methane can be computed and reported under the EPA rule. Infrequent snapshot measurements have limited ability to characterize emission duration due to the relatively low frequency at which they observe a given source. For example, an aerial measurement campaign measuring each site quarterly will only be able to bound emission start times at three month intervals, despite emissions potentially lasting for only a few hours or days. Satellites can provide more frequent measurements of a given source, but their current operational detection limits are greater than the 100 kg/hr threshold and cloud cover and surface albedo can also prevent detections. Higgins et al. propose methods for bounding emission durations using operational data, such as tank pressures from a Supervisory Control and Data Acquisition (SCADA) system. They note that these methods will be useful to oil and gas operators for near-term regulatory compliance as measurement-based methods for estimating emission durations evolve, such as more frequent aerial sampling or supplementing snapshot measurements with continuous monitoring systems (CMS). Here we develop a method for estimating methane emission durations using point-inspace CMS. These sensor systems measure methane concentrations in near-real time at several fixed sensor locations, typically around the perimeter of oil and gas sites. In practice, 1 to 10 CMS sensors may be installed on a given site, depending on its complexity and the CMS technology vendor, with most production sites having around 4 sensors. For reference, Figure in the Supporting Information (SI) file shows a typical oil and gas production site with point-in-space CMS sensors arranged around the perimeter.