Gas year

A gas year consists of the period between 6am on 1 October of a given year and 6am on 1 October of the following year.

The gas year is not the same as the financial year because contracts were traditionally negotiated before the start of the cold weather.

Marker post

Orange signpost, about 2.50 to 3 metres high, which enables the path of an underground pipe to be tracked either at ground level or from the air (e.g. from a helicopter).


Marker posts form an integral part of pipeline transportation installations.


Unit of measurement of fluid pressure.

The unit of pressure derived from the International System of Units (SI) is the pascal (Pa). The pascal is the uniform pressure that exerts a total force of one newton perpendicularly upon a plane surface of one square metre.

1 bar corresponds to 100,000 Pa, or about 1 kg/cm2. Normal atmospheric pressure, for example, is around 1 bar. Gas is delivered to the end consumer (e.g. for a boiler) at 20 millibars.


Gas produced by the fermentation of animal or vegetable organic materials in the absence of oxygen. This fermentation, which is also known as methanisation, occurs naturally in swamps and spontaneously in dumps containing organic waste.

Find out more about biogas

Network capacity

The network’s capacity to transport a certain hourly volume of natural gas, from the injection point to the delivery point. This capacity is stated in nm3/h.


“Since gas is compressible, it is possible to change the volume of a given amount of gas by compressing it or changing its temperature. It is therefore impossible to know the mass of a quantity of gas based on its volume without giving the pressure and temperature of the gas at the time when the volume was measured.


 It would be unnecessarily complicated to give a temperature and pressure every time a volume of gas is mentioned, so the temperature and pressure at the time when the volume was measured are standardised to “normal” conditions. This is called normal m3.


Definition adapted from  

Cornaux power station

Combined-cycle gas turbine plant (gas turbine and steam turbine) that generates electricity.

Combined-cycle gas turbine plant (gas turbine and steam turbine) that generates electricity.

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CO2, which is also known as carbon dioxide or carbonic gas, is a colourless, inert, non-toxic gas.

It has numerous natural sources: volcanic eruptions, plant, animal and human respiration, forest fires, decomposition of organic material, combustion, etc.

The principal greenhouse gas. Owing to human activity, concentrations of CO2 in the atmosphere are rising by 0.5% per year on average. To given an order of magnitude, a 30% increase over the past two centuries has been measured.


Cogeneration is a method of producing electricity and heat simultaneously.


Saturation of the gas transportation network that limits the opportunity for commercial transactions. This regularly occurs at the borders between the European countries, and partly accounts for the persistent differences in market prices in Europe.

Interruptible consumer

Generally, these are consumers who are able to switch to an energy other than gas if necessary. A fuel switch is made at the request of the gas distributor or transporter.

Gas volume corrector

Device which converts the volume measured by a gas meter into a volume of gas under normal conditions (1.01325 bar abs./0°C).

Rate per hour

Quantity of natural gas transported per full hour, expressed in nm3/h.


The ratio of the masses of two equal volumes of gas and air, each under identical reference conditions. Gases lighter than air have a density lower than 1 and gases heavier than air have a density higher than 1.