Reference Gas Standards

To ensure compatibility of of the ICOS atmospheric greenhouse gas observations with data from other global monitoring networks, the measurements need to be traceable to the respective WMO calibration scales. The FCL is responsible for providing real air reference gas standards for ICOS atmospheric observations.

Calibration is done using a set of WMO laboratory standards calibrated by the Central Calibration Laboratory ☛. The concentration ranges covered by this set for the individual trace gases can be found below.
FCL WMO calibration standards

Please contact us via

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WMO scale link via set of primary references

UCN	CO₂ [ppm]¹	CH₄ [ppb]²	CO [ppb]³	N₂O [ppb]⁴	SF₆ [ppt]⁵
CB09948	250.08	2932.82	998.63	362.13	10.71
CB09944	339.24	1596.64	31.31	316.77	6.49
CB09939	365.16	1743.13	80.14	319.86	7.47
CB09958	389.53	1896.82	120.69	327.12	8.51
CB09983	412.21	2032.92	158.92	329.92	9.16
CB09952	433.58	2195.34	199.47	334.60	10.10
CB09955	458.92	2344.05	247.14	339.48	13.20
CB09957	481.75	2466.72	397.06	343.95	12.20
CB09934	514.80	2731.28	697.56	349.13	21.35

WMO scale

¹ CO2_X2007
² CH4_X2004A
³ CO_X2014A
⁴ N2O_2006A
⁵ SF6_X2014

How to get reference gas standards?

Important note!

Tanks have to be provided by you with valid certificates.
If you have to purchase new tanks please anticipate the distributor's delivery time and an extra period of two months at the FCL for initial conditioning the tanks.

Contact in advance

Please notify us via Please enable Javascript to view at least three months in advance (see section "Calibration" in the ICOS Atmospheric Station Specification ☛) if you want to order reference gas standards.

Provide tank metadata

If the tank have never been registered and analyzed at the FCL until now, please make sure to provide following tank and valve metadata via Please enable Javascript to view. Otherwise the FCL is not able to register and analyze your tank.

^* REQUIRED FIELDS

Attribute	Example
Owner^*	EMPA, Überlandstrasse 129, 8600 Dübendorf, Switzerland
Responsible person^*	Ms. Jane Doe
Volume^*	50 l
Manufacturer^*	Luxfer Gas Cylinders UK, Nottingham, United Kingdom
Serial number	D760321
Material Body^*	Alu (AA6061)
Inner coating
Valve manufacturer^*	Rotarex
Valve type^*	D200
Valve connector^*	DIN14
Valve material body^*	Brass
Valve material seat	PCTFE-sealing
Valve has burst disc	yes/no

Template tank metadata

Provide requested composition list

Provide your requested concentration list (according to "Standard air mixture for ICOS stations" ☛) via email to Please enable Javascript to view. For submitting the list of requested mole fractions, we kindly ask to use the following template files.

Template for reference gas set compositionX

The following tables specify the mole fractions recommended by the the ATC, see also Standard air mixture for ICOS stations ☛ version 2.1 (2023-09-25).

The appropriate composition of your calibration (CAL) and longterm target (LTT) gases will depend on the location of your station (background site or regional site with more anthropogenic influence). For the shortterm target (STT) or short term working standards for LGR measurements it is generally sufficient to use ambient air without specific composition requirements.
Please note that the mole fractions we can provide have to remain within the range spanned by the FCL set of WMO calibration standards.

Background stations

Periurban stations

3 CAL set (background)

3 CAL set (periurban)

4 CAL set (background)

4 CAL set (periurban)

Send tank

Send your tank to:

ICOS - Flask and Calibration Laboratory
Technologie Center Felsenkeller (TCF), Eingang A
Kahlaische Straße 4
D-07745 JENA
GERMANY