Trace gas handling and monitors

Contact: Dr. Harald Saathoff

AIDA trace gas handling system:

For the controlled supply of trace gases to the AIDA simulation chamber a stainless steel vaccum system is used. It allows for quantitative addition of trace gases from gas cylinders, glas bulbs, or cooling traps. Quantification is realised by using certified gas cylinders, by measuring the vapour pressure (4 MKS Baratron ranges: 10 hPa, 100 hPa, 1000 hPa, 30000 hPa) of trace gases in the glas bulbs or cylinders, and by controlling the volume added to the AIDA chamber using calibrated mass flow controllers.

AIDA trace gas monitors:

The trace gas monitors are connected to the AIDA chamber via Teflon (FEP) tubes ranging ~40 cm into the chamber. Sampling is done either continously or intermittent using automated valves. Signal output of the gas monitors is directly connected to the AIDA data aquisition & visualisation system and stored in the AIDA database.

Ozone concentrations are measured by UV absorption:

Ozone Instuments

 Measurement range Detection limit  Sample flow Calibration
Environment O341M  0 - 10 ppm  1 ppb  0.5 l/min

Ansyco GmbH

Monitor Labs 9811  0 - 20 ppm  1 ppb  0.5 l/min comparison with reference instrument

NO/NO2 concentrations are measured by fluorescence and photolytic conversion using a combination of two instruments and by Cavity Attenuated Phase Shift (CAPS):

NO/NO2 Instruments  Measurement ranges Detection limit Sample flow Calibration
ECO Physics CLD 77 AM  0 - 10, 100, 1000, 10000 ppb  20 ppt  50 - 350 ml/min certified gas mixtures
ECO Physics PLC 760 MH  selective conversion of NO2 into NO with UV (320-420nm)  - " certified gas mixtures
Environment AF32M (NO2)  0-1 ppm (CAPS)  0.1 ppb  1 l/min certified gas mixtures

SO2 concentrations are measured by fluorescence:

SO2 Instrument  Measurement ranges Detection limit Sample flow Calibration
Environment AF22M  0-0.1/ 0.2 / 0.5 /1 / 2 / 5 / 10 ppm  1 ppb  300 ml/min certified gas mixtures