U.K. National Radiological Protection Board Radon Calibration Procedures

A procedure for the calibration of instruments for the detection of (222)Rn in air is described. The method is based on the alpha-spectrometric determination of the concentration in air of (218)Po in the calibration chamber. The calibration chamber is described, together with the method of maintaining a high aerosol concentration. The (218)Po concentration at steady state in the chamber is found to be 98% of the (222)Rn concentration typically. An assessment of the sources of uncertainty in the method presented indicate that the (222)Rn concentration in the chamber can be determined with an overall uncertainty of about 7% at the 95% confidence level.