Glossary:Detection

A determination that a source may be present. Typically requires on analysis of one or a series of measured anomalies. Detections can be defined in terms of magnitude and/or duration of elevated mixing ratio or emission rate. For example, a detection event could be defined as an anomaly that reaches an estimated mass emission rate of 5 standard deviations above a 24-hour baseline Unlike an anomaly, a detection is intended to lead to a further action, e.g., follow-up and/or root-cause analysis.

Detection threshold – The minimum quantity or concentration of a gas (e.g. methane) that is reliably detectable by detection equipment. This is sometimes called the minimum detection limit (MDL). Detection limits can vary based on the type of technology selected as well as the conditions during the measurement period. Probability of detection is a preferred concept because the minimum is context dependent.

Minimum Detection Limit – The highest flow rate at which a measurement technology is required to detect emissions with 90% probability. Technology with a higher MDL is less sensitive than technology with lower MDL. The MDL is also referred to as the minimum detection threshold. The smallest atmospheric concentration or emission rate that a measurement method capable of discerning above background.

Or

Methane Emission Detection:

Process of identification of methane emissions from potential sources, without the measurement of the mass quantity (flow rate, e.g. kg/h). Several devices, screening instruments and methodologies are available to detect methane emissions, including optical gas imaging cameras, laser leak detectors, portable analysers (OVAs, TVAs), soap bubble screening and/or AVO methods. Some of these are able to detect and provide a concentration level (volume, e.g. ppmv) that can be used to estimate the mass emission (e.g. by applying specific emission factors or correlation equations available from literature).