ACTRIS JUNOx23 intercomparison startes
19 Jun
30 Jun

JUNOx23 NO/NO2 Intercomparison campaign

Our goal is to improve the quality of NOx measurements through standardized calibration procedures and experiments to investigate the effects of interfering factors such as water vapor, ozone (O3), nitrous acid (HONO), and glyoxal (C2H2O2). The intercomparison campaign is conducted in the summer of 2023 (June 19-June 30, 2023) at the SAPHIR atmospheric simulation chamber and at the JULIAC tower at the Institute for Energy and Climate Research (IEK-8 Troposphere) of Forschungszentrum Jülich. The interlaboratory test campaign is part of the QA/QC measures for the ACTRIS national facilitities.


SAHPHIR-Chamber (Left) und JULIAC-Tower (Right)

The devices are installed in containers under the SAPHIR atmosphere simulation chamber. They are connected to a common sampling line that can be used to take air samples from the top of the JULIAC tower or from a calibration system.


Addition of Trace gases

Lukas Kesper (left) and Benjamin Winter (right) set up the CEM (Controlled Evaporation and Mixing) system for the ACTRIS-NOx comparison campaign.

Standard gases and interfering gases are added to the common inlet line from a homemade calibrator. The air can be spiked with hydrocarbons or compounds such as formaldehyde and glyoxal from prepared cylinders or a thermobalance.


Junox23 particpants


In total there are 15 partners with 36 instruments.


FZ Jülich, Germany, (CiGas)

CLD (Chemiluminescence Detector)

5 ICAD (Iterative cavity-enhanced DOAS)

TDL (Tunable Diode Laser)


Airyx, Germany

ICAD (Iterative cavity-enhanced DOAS)

Federal Highway Resaerch Institute, BAST, Germany

Photoaccustic Sensors

CNR - ISAC, Monte Cimone, Italy

2 CLD (Chemiluminescence Detector)

University College Cork, Ireland

CEAS (Incoherent Broadband Cavity-Enhanced Absorption Spectrometer)

German Weather Sevice, Germany (CiGas)

3 CLD (Chemiluminescence Detector)

2 CAPS (Cavity attenuated phase shift spectroscopy)

University of Frankfurt, Germany

CLD (Chemiluminescence Detector)

CNRS-Orléans, France

CLD (Chemiluminescence Detector)

2 CAPS (Cavity attenuated phase shift spectroscopy)

University of Iasi, Romania

CLD (Chemiluminescence Detector)

IMT, France (CiGas)

2 CLDs (Chemiluminescence Detector)

CAPS (Cavity attenuated phase shift spectroscopy)

University of Leicester, UK

CAPS (Cavity attenuated phase shift spectroscopy)

University of Nottingham, UK

ICAD (Iterative cavity-enhanced DOAS)

University of Wuppertal, Germany

CLD (Chemiluminescence Detector)

LOPAP (Long-Path-Absorption-Photometer)

TROPOS, Germany

3 CLD (Chemiluminescence Detector)

CAPS (Cavity attenuated phase shift spectroscopy)

University of York, UK

ICAD (Iterative cavity-enhanced DOAS)


The setup of the instruments started June 12, 2023.

  • Comparison of gas standards and calibration setups
  • Test for humidity,formaldehyde, HONO and ozone interferences
  • Ambient measurements from the JULIAC-tower
  • Discussion of intercomparison results on a daily basis
  • Instrument training

Please contact:

Robert Wegener, Forschungszentrum Jülich,

Max Gerrit Adam, Forschungszentrum Jülich,