As in previous years, an intercomparison of passive radon detectors was organised by and held at the Radiation Protection Division of the Health Protection Agency in 2007. Thirty-six laboratories submitted 49 sets of passive detectors to this intercomparison. The exercise included three exposures to radon and its decay products at different equilibrium factors.
After exposure, the detectors were returned to their originating laboratories for assessment. Participants reported the estimated exposure for each detector before they were notified of the exposures given to the detectors. The results obtained by participating laboratories were classified according to the spread of results from detectors exposed together and by the difference between the mean result of each group and the actual exposure given.
Thirty-five per cent of the laboratories achieved the highest classification for accuracy, while 9% were in the lowest category. The proportion of laboratories achieving very good results is broadly in line with that seen in recent intercomparisons. Each year a number of laboratories introduce new detector systems which often results in initially less successful performance. As experience is gained, it is expected that results from laboratories operating such systems will improve.