Tropospheric Chemistry: VOC Instruments

Integrated Whole Air Sampler (iWAS)

iWAS instrument
iWAS installed on NOAA WP-3D research aircraft. Photo: M. Dechesne

Principle of the Measurement

Collect whole air samples for offline analysis via gas chromatography-mass spectrometry (GC-MS). Whole air samples are primarily used aboard research aircraft and mobile laboratories or in places where the GC-MS cannot be easily deployed or when on-demand sampling is required. The integrated whole air sampling system (iWAS) consists of a high-volume stainless steel bellows compressor (Senior Aerospace 28823-11) connected in series with rack-mounted modules containing twelve (12), 1.4 L electropolished stainless steel canisters that are individually isolated from the sampling manifold by pneumatically actuated stainless steel bellows valves. The sample collection is computer controlled and can be operated in survey mode using a set time interval or on-demand for targeted plume analysis.

Species Measured

whole air

Time Response / Detection Limit

For airborne sampling, canisters fill times range from 3-10 seconds depending on altitude. For ground-based sampling, fill times can range from 3 seconds to several minutes depending on sampling strategy. It takes 20 minutes to analyze each sample on the NOAA GC-MS.

Manufacturer

Custom designed and machined by National Center for Atmospheric Research (NCAR) Design and Fabrication Services (DFS)

Field Projects

Key Publications

Lerner, B.M., J.B. Gilman, K.C. Aikin, E.L. Atlas, P.D. Goldan, M. Graus, R. Hendershot, G.A. Isaacman-VanWertz, A. Koss, W.C. Kuster, R.A. Lueb, R.J. McLaughlin, J. Peischl, D. Sueper, T.B. Ryerson, T.W. Tokarek, C. Warneke, B. Yuan, and J.A. de Gouw, An improved, automated whole-air sampler and gas chromatography mass spectrometry analysis system for volatile organic compounds in the atmosphere, Atmospheric Measurement Techniques, doi:10.5194/amt-10-291-2017, 2017.