To support the industry and stakeholders in the use of consistent terminology, Ipieca, IOGP, GIE and MARCOGAZ prepared this methane emissions glossary covering the whole natural gas value chain.

Intended for policymakers and regulators working on methane regulation in Europe, this glossary will be updated to reflect new legislation and technologies.

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There are currently 11 names in this directory beginning with the letter S.

Evaluations with the main purpose of identifying sources of emissions. In many contexts, screening can be the same as surveying. However, in some regulatory contexts, screening applies only to less rigorous or less sensitive detection approaches, such as AVO (Audio, Visual, and Olfactory). [14]

Part of the complete gas value chain. [12] (Note: The oil and gas industry is usually divided into three major sectors: upstream (or exploration and production - E&P), midstream and downstream.)

Service lines
The pipework from the main lines to the point of delivery of the gas into the installation pipework. [2]
(Note: Service line is usually a short, small diameter pipeline that delivers gas from distribution main or transmission pipeline to the customer. They are usually made of steel pipe or steel tubing (either cathodically protected or not), or plastic (usually polyethylene, but sometimes PVC or other plastic), although copper tubing was also used in the past. Service lines can be installed under or above ground. Note: Cathodic protection is a technique used to mitigate the corrosion of a metal surface by making it act as an electrical cathode)

Soap bubble screening (“soaping”)
A quick and low-cost leak detection technique. This method involves squirting a soap solution on small and accessible components such as flanges, valves, fittings, threaded connections, etc. If there is a leak, soap bubbles will develop from the solution. Soaping is effective for locating loose fittings and connections. It is not effective on large openings such as open ended pipes or vents. [16]

A component within a process or equipment that releases methane to the atmosphere either intentionally or unintentionally, intermittently or persistently. [12]

A temporary seal, plug or stopper. They are used to repair pipelines, or to isolate (cut off) a section of pipeline where there is no existing shut-off valve. [15]

Storage facility
A facility used for the stocking of natural gas and owned and/or operated by a natural gas undertaking, including the part of LNG facilities used for storage but excluding the portion used for production operations, and excluding facilities reserved exclusively for transmission system operators in carrying out their functions. [1]

Storage system operator (SSO)
A natural or legal person who carries out the function of storage and is responsible for operating a storage facility. [1]

– Methane emission source that represent a disproportionate amount of the total methane emissions released from all sources. (Note - The term ‘super-emitter’ can refer to malfunctioning equipment, particularly in unmanned installations where such equipment has the potential to exist for long periods of time. The determination of a super-emitter is best associated with emissions data from a given source and should not be viewed as an attribute of an entire site. Care should be taken when utilizing methodologies for identifying super-emitters to differentiate between episodic events (e.g. gas actuation events), erroneous measurements and/or malfunctioning equipment. The term ‘fat-tail’ is often used to describe the statistical anomalously high values from a small number of sources seen from representation of the data—a probability distribution that is highly skewed relative to a well-behaved distribution such as the normal or an exponential distribution. Having super-emitters at a few sites could skew significantly the distribution of emissions from a sample of sites.)

Using detection equipment and measurements to examine a group of assets for signs of emissions. [14]

System integrity
Any situation in respect of a gas network including necessary assets in which the pressure and the quality of the gas remain within the minimum and maximum limits laid down by the system operator, so that the operation is guaranteed from a technical standpoint. [17]


[1] Directive 2009/73/EC of the European Parliament and of the Council of 13 July 2009

[2] EN-12186 – Gas infrastructure – Gas pressure regulating stations for transmission and distribution – Functional requirements

[3] EN-12327 – Gas infrastructure – Pressure testing, commissioning and decommissioning procedures – Functional requirements

[4] EN-12583 – Gas Infrastructure – Compressor stations – Functional requirements

[5] EN-15446 – Fugitive and diffuse emissions of common concern to industry sectors – Measurement of fugitive emission of vapours generating equipment and piping leaks

[6] GIE & MARCOGAZ Report “Potential ways the gas industry can contribute to the reduction of methane emissions”

[7] IPIECA/API/IOGP (2020). Oil and gas industry guidance on voluntary sustainability reporting

[8] IPIECA Methane Glossary

[9] ISO 14532 – Natural gas — Vocabulary

[10] JCGM-100 – Evaluation of measurement data – Guide to the expression of uncertainty in measurement. s.l.: Committee for Guides in Metrology (JCGM/WG 1), 2008

[11] MARCOGAZ – Assessment of methane emissions for gas Transmission and Distribution system operators, 2019 Assessment+of+methane+emissions+for+gas+Transmission+and+Distribution+system+ operator.pdf?t=1602849054

[12] MARCOGAZ – Guidance for using the MARCOGAZ methane emissions reporting template – DSO, TSO, LNG receiving terminals and UGS

[13] MGP Reducing methane emissions: Equipment leaks

[14] MGP Reducing methane emissions: Identification, detection, measurement and quantification

[15] MGP Reducing methane emissions: Transmission, storage, LNG terminals and distribution

[16] Oil and Gas Methane Partnership Technical Guidance Documents

[17] Regulation (EC) No 715/2009 of the European Parliament and of the Council of 13 July 2009

[18] US EPA – ‘Method 21: Determination of volatile organic compound leaks’