An electrostatic integrating 222Rn monitor with cellulose nitrate film for environmental monitoring.

This paper describes a new type of electrostatic integrating 222Rn monitor designed for the environmental 222Rn monitoring. The window area of the monitor was selected to make the exchange rate optimal. The collecting electrode was positioned on the basis of calculating the internal electric field. A drying agent, P2O5, was placed in the bottom of the monitor, since the collection efficiency of 218Po+ atoms depends on the humidity of the air. The monitors have been calibrated against known 222Rn exposures. The detection limit is 1.2 Bq m-3 for an exposure time of 2 mo. In a small survey, annual mean 222Rn concentrations between 3.7 and 9.5 Bq m-3 in outdoor air and between 6.4 and 11.9 Bq m-3 in indoor air were measured.