Flask or bag samples are usually made in remote areas where it would be impractical to have a continuous instrument running. These samples are taken back to the lab for analysis.
Sampling methane emissions from cows in Zimbabwe
Flask or bag samples are also taken to measure methane isotopes. Instrumentation to measure these species are unsuitable for remote stations, primarily because they need near continuous technical attention but also due to their large size (see below) and use of consumable gases.
The large isoprime mass spectrometer and trace gas pre-concentrator is used to measure methane isotope in the lab at Royal Holloway
Collecting an air sample in a Tedlar bag