Obtaining a sample of the atmosphere in a period which is short compared with the duration of the sampling exercise. Such samples are often called 'grab' samples, a term not recommended. These are useful for the analysis of @H02889@ and other complicated mixtures of trace gases which are relatively @S05900@ in a stainless steel canister or tank and can be transported back to the laboratory for chromatographic or other analysis which cannot be done satisfactorily in the field.