U.K. National Radiological Protection Board Radon Calibration Procedures

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