Field experience with volume traps for assessing retrospective radon exposures

About two hundred volume traps were retrieved from dwellings in various radon prone areas inEurope. They were analysed for the purpose of retrospective radon assessment. Emphasis is put onspecific problems encountered when using field samples as opposed to laboratory exposed samples. Itwas seen that in very dusty circumstances, direct penetration of radon decay products from the outsideto the centre of the volume traps calls for extra caution. Rinsing the samples is proposed as a solutionand was tested in field and laboratory conditions, showing good results. An attempt was made to givean assessment of the achievable accuracy of the method. Where possible, the volume trap retrospectiveresults were compared to contemporary measurements or to retrospective results from surface traps.The overall impression is that although volume are sometimes hard to find in the field, the highreliability of the results makes it well worth doing the effort.