A second intercomparison of 222Rn measurement systems in European laboratories

A recent intercomparison exercise (established under the auspices of EUROMET) involving seventeen laboratories was conducted by NPL, who generated and standardised a set of glass-encapsulated 222Rn samples and then dispatched a unique subset of the samples to each participant. The reported measured activities of the samples were normalised to the NPL values. The spread of results, for the laboratories who had participated in an earlier exercise, was of the order of ± 5%; the results of 12 of the participants agreed at the 1 σ level.