Comparison Display

BIPM.QM-K2.b

MEASURAND Amount fraction of CO₂ in nitrogen

NOMINAL VALUE 350 µmol/mol to 430 µmol/mol

Degrees of equivalence represented by D_i = (x_i - x_R) and its expanded uncertainty U_i at a 95 % level of confidence, both expressed in µmol/mol.

Amount fraction of CO₂in nitrogen

D_i / μmol mol^-1

Participating institutes

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BIPM.QM-K2.b

MEASURAND Amount fraction of CO₂ in nitrogen

NOMINAL VALUE 430 µmol/mol to 530 µmol/mol

Degrees of equivalence represented by D_i = (x_i - x_R) and its expanded uncertainty U_i at a 95 % level of confidence, both expressed in µmol/mol.

Amount fraction of CO₂in nitrogen

D_i / μmol mol^-1

Participating institutes

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BIPM.QM-K2.b

MEASURAND Amount fraction of CO₂ in nitrogen

NOMINAL VALUE 530 µmol/mol to 800 µmol/mol

Degrees of equivalence represented by D_i = (x_i - x_R) and its expanded uncertainty U_i at a 95 % level of confidence, both expressed in µmol/mol.

Amount fraction of CO₂in nitrogen

D_i / μmol mol^-1

Participating institutes

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BIPM.QM-K2.b

MEASURAND Amount fraction of CO₂ in nitrogen

NOMINAL VALUE 350 µmol/mol to 430 µmol/mol

Degrees of equivalence represented by D_i = (x_i - x_R) and its expanded uncertainty U_i at a 95 % level of confidence, both expressed in µmol/mol.

	LAB_i	D_i	U_neg,i	U_pos,i
		μmol mol-1	μmol mol-1	μmol mol-1
	E+E	0.40	4.45

Participating institutes

BIPM.QM-K2.b

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BIPM.QM-K2.b

MEASURAND Amount fraction of CO₂ in nitrogen

NOMINAL VALUE 430 µmol/mol to 530 µmol/mol

Degrees of equivalence represented by D_i = (x_i - x_R) and its expanded uncertainty U_i at a 95 % level of confidence, both expressed in µmol/mol.

	LAB_i	D_i	U_neg,i	U_pos,i
		μmol mol-1	μmol mol-1	μmol mol-1
	E+E	4.55	4.02

Participating institutes

BIPM.QM-K2.b

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BIPM.QM-K2.b

MEASURAND Amount fraction of CO₂ in nitrogen

NOMINAL VALUE 530 µmol/mol to 800 µmol/mol

Degrees of equivalence represented by D_i = (x_i - x_R) and its expanded uncertainty U_i at a 95 % level of confidence, both expressed in µmol/mol.

	LAB_i	D_i	U_neg,i	U_pos,i
		μmol mol-1	μmol mol-1	μmol mol-1
	E+E	7.38	4.13

Participating institutes

BIPM.QM-K2.b

Comparison

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BIPM.QM-K2.b

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Information & contact
Participants

Metrology area, Sub-field	Chemistry and Biology, Gases
Description	Carbon dioxide in nitrogen
Time of measurements	2024 -
Status	Continuous, approved for equivalence

References	BIPM.QM-K2 Technical protocol and instructions for participation
Measurand	Amount fraction of carbon dioxide in nitrogen from 350 μmolmol^-1 to 800 μmol mol^-1
Transfer device	High pressure cylinders

Comparison type	Key Comparison
Consultative Committee	CCQM (Consultative Committee for Amount of Substance)
Conducted by	BIPM (Bureau International des Poids et Mesures)
Comments	BIPM.QM-K2 is an on-demand key comparison for gaseous standards of CO₂ in dry air (part a) or in nitrogen (part b) contained in high pressure cylinders. The key comparisons BIPM.QM-K2.a and b are aimed at underpinning the capabilities of the participants to value assign the amount fraction of CO₂ in air (part a) or in nitrogen (part b) in gas standards over the amount fraction range from 350 μmol mol⁻¹ to 800 μmol mol⁻¹, with a method ensuring traceability of the measurements to the SI. The comparison is run as a series of bilateral comparisons between each participant and the BIPM. The facility maintained by the BIPM (the so called the CO₂-PVT facility) provides the key comparison reference value in each case and quantifies CO₂ amount fractions in air or nitrogen samples via measurements of the pressure and temperature of the sample and of the CO₂ extracted from it by cryogenic trapping. First results published on 06 August 2025 The Final Report for each bi-lateral comparsion is listed in the tab "Participants" Most recent update: 06 August 2025
Pilot institute	BIPM Bureau International des Poids et Mesures BIPM - International Organization
Contact person	J. Viallon +33 (0) 1 47 07 62 70

Pilot laboratory
BIPM	Bureau International des Poids et Mesures, BIPM - International Organization, N/A

E+E	E+E Elektronik, Austria, EURAMET
Mar 2025	Metrologia 2025 62 Tech. Suppl. 08022

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BIPM.QM-K2.b

MEASURAND Amount fraction of CO₂ in nitrogen

NOMINAL VALUE 350 µmol/mol to 430 µmol/mol

The key comparison reference value is the results of measurements performed at the BIPM x_R(CO₂) with their standard uncertainties u_R(CO₂) available in the laboratory measurement tab.

The degree of equivalence of laboratory i relative to the key comparison reference value x_R is given by a pair of terms, both expressed in µmol/mol:

D_i = (x_i - x_R) and its expanded uncertainty U_i at a 95 % level of confidence where U_i = 2 (u_i+ u_R )^1/2 .

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BIPM.QM-K2.b

MEASURAND Amount fraction of CO₂ in nitrogen

NOMINAL VALUE 430 µmol/mol to 530 µmol/mol

The key comparison reference value is the results of measurements performed at the BIPM x_R(CO₂) with their standard uncertainties u_R(CO₂) available in the laboratory measurement tab.

The degree of equivalence of laboratory i relative to the key comparison reference value x_R is given by a pair of terms, both expressed in µmol/mol:

D_i = (x_i - x_R) and its expanded uncertainty U_i at a 95 % level of confidence where U_i = 2 (u_i+ u_R )^1/2 .

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BIPM.QM-K2.b

MEASURAND Amount fraction of CO₂ in nitrogen

NOMINAL VALUE 530 µmol/mol to 800 µmol/mol

The key comparison reference value is the results of measurements performed at the BIPM x_R(CO₂) with their standard uncertainties u_R(CO₂) available in the laboratory measurement tab.

The degree of equivalence of laboratory i relative to the key comparison reference value x_R is given by a pair of terms, both expressed in µmol/mol:

D_i = (x_i - x_R) and its expanded uncertainty U_i at a 95 % level of confidence where U_i = 2 (u_i+ u_R )^1/2 .

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BIPM.QM-K2.b

MEASURAND Amount fraction of CO₂ in nitrogen

NOMINAL VALUE 350 µmol/mol to 430 µmol/mol

x_i measured mass fraction reported by laboratory i, Lab_i

u_i combined standard uncertainty of x_i

Lab_i	x_i	u_i	x_R(CO₂)	u_R(CO₂)	date of
Lab_i	µmol/mol	µmol/mol	µmol/mol	µmol/mol	measurement
E+E	401.78	2.23	401.38	0.10	Mar-25

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BIPM.QM-K2.b

MEASURAND Amount fraction of CO₂ in nitrogen

NOMINAL VALUE 430 µmol/mol to 530 µmol/mol

x_i measured mass fraction reported by laboratory i, Lab_i

u_i combined standard uncertainty of x_i

Lab_i	x_i	u_i	x_R(CO₂)	u_R(CO₂)	date of
Lab_i	µmol/mol	µmol/mol	µmol/mol	µmol/mol	measurement
E+E	503.88	2.01	499.33	0.12	Mar-25

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BIPM.QM-K2.b

MEASURAND Amount fraction of CO₂ in nitrogen

NOMINAL VALUE 530 µmol/mol to 800 µmol/mol

x_i measured mass fraction reported by laboratory i, Lab_i

u_i combined standard uncertainty of x_i

Lab_i	x_i	u_i	x_KCRV	u_KCRV	date of
Lab_i	µmol/mol	µmol/mol	µmol/mol	µmol/mol	measurement
E+E	707.64	2.06	700.26	0.17	Mar-25

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