Standards, calibration and quality assurance of 222Rn measurements in Sweden

Abstract

Inhaled decay products of 222Rn are the dominant components of the natural radiation exposure to the general population. Limits have been introduced in Sweden, and recommendations were made in 1980 for decreasing indoor 222Rn concentration. The need for the coordinated calibration of measuring instruments as well as for quality assurance was obvious for both health and economic reasons. 222Rn measurements in Sweden are based on standards traceable to the National Institute of Standard and Technology (NIST) through the use of standard reference material 226Ra. Standards for both 222Rn and short-lived 222Rn progeny are described together with the reference instrument adopted for these studies. The calibration of field instruments was performed in a “radon room”, a climate chamber in which it is possible to vary and monitor the concentration of 222Rn as well as other characteristics of the indoor air such as temperature, humidity, ventilation rate and aerosol concentration. The rules and regulations for field measurements imply a calibration of the instruments yearly, as well as accreditation and training for the companies that carry out the measurements. Examples are given of the official measurement protocols used for the different types of instruments.