Improving gas analyses when diluting air samples by using background air

Air samples collected for the purpose of assessing whether a region is a source or a sink of a gas species must often be pressurised (and hence diluted) prior to instrumental analysis. An inert gas is the obvious choice for a diluent, but an error analysis, which indicates that in specific circumstances use of background air for pressurisation can mitigate degradation of precision due to dilution, is presented. The analysis, which is based upon a simple statistical theory, provides quantitative guidance as to the limits of the techniqueʹs applicability.