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 5 names in this directory beginning with the letter T.

Third-party damage
Any accidental damage caused to a natural gas system as a result of activities not associated with the system. Examples are excavations or other private or public works that are performed by parties not associated with the gas supply (for example, work on water mains).

Top-down emission approach
Estimate made using different remote sensing based techniques, e.g. satellite and airborne, to measure ambient air concentrations of methane, calculate methane flux based on atmospheric and meteorological conditions, and then attribute the emission to different activities. Each measurement technique has different resolution capabilities, strengths and weaknesses. (Note - Methane emissions are allocated to the natural gas industry by: (a) using a ratio of methane to ethane or propane (longer chain aliphatics which do not occur from biogenic sources); (b) isotopic ratio analysis, using a co-located tracer (such as SF6 or C2H2); or (c) subtracting estimates of other sources of methane emissions such as, livestock, wetlands, agriculture, waste management, etc. together with background methane concentrations.)

Toxic Vapour Analyser (TVA)
Portable hydrocarbon detector that can be utilised to identify methane leaks. (Note - For higher concentration leaks, a TVA combines a flame ionization detector (FID), which is particularly sensitive to methane, with a photoionization detector (PID), which is sensitive to other hydrocarbons but insensitive to methane. In combination, OVAs and TVAs can measure the methane concentration in the area surrounding a leak over a large range.)

The transport of natural gas through a network, which mainly contains highpressure pipelines, other than an upstream pipeline network and other than the part of high- Glossary on methane emissions 15 pressure pipelines primarily used in the context of local distribution of natural gas, with a view to its delivery to customers, but not including supply. [17]

Transmission System Operator (TSO)
A natural or legal person who carries out the function of transmission and is responsible for operating, ensuring the maintenance of, and, if necessary, developing the transmission system in a given area and, where applicable, its interconnections with other systems, and for ensuring the long-term ability of the system to meet reasonable demands for the transport of gas. [1]


[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’