Online air or gas sampling
‘Whole air’ sampling refers to collection of samples in the field using canisters or bags, or their direct introduction to the focusing trap of the thermal desorption instrument without the use of sorbent tubes (online sampling). The compounds remain in the gas phase throughout.
Air sampling bags are commonly used to collect whole air samples for landfill gas and soil gas. A sample can be collected in the container using either pumped or passive sampling, and subsequently sealed and transported to the laboratory for analysis.
Where the compounds of interest are too volatile to be retained by sorbent tubes at ambient temperature (such as hydrogen sulfide), either on-line or canister analysis is required (as opposed to tube sampling).
On-line air monitoring is the method of choice for real-time monitoring of changes in vapour concentrations and for continuous remote monitoring.
Key applications include:
- Ozone precursor monitoring
- Odours in urban air
- Fenceline monitoring of petrochemical plants and other industrial installations
- Odour from sewage treatment works