AS 2365.4-1995

Sets out three methods for the determination of the radon content in indoor air. Method A applies to grab samples and requires the collection of a grab sample in a scintillation cell followed by the measurement of its alpha activity. Method B is applicable for short-term sampling periods. The principle consists of adsorption of the radon onto activated charcoal followed by the measurement of the gamma radiation that is emitted. Method C applies to sampling periods of up to a year and employs solid state nuclear track monitoring.

This Standard sets out three methods for the determination of the radon content of indoor air. The methods are as follows:(a) Collection in scintillation cells and measurement of alpha activity (Method A)* Applicable for grab samples (sampling times of a few seconds) and providing a rapid means of obtaining a radon concentration at a particular time. Its detection limit is dependent on the background count rate. For a background count rate of 1 count/min and a counting period of 60 min, the lower detection limit is 40 Bq/m3. For a scintillation cell with a sampling volume of 140cm3, the sensitivity of the method is approximately 0.019 counts/min per Bq/m3in air.å(b) Passive adsorption onto activated charcoal and measurement of gamma radiation (Method B) Applicable for short term sampling (between 1 d and 7 d). The detection limit is approximately 15 Bq/m3for an exposure period of 4 d and counting period of 60 min.(c) Solid-state nuclear track monitoring (Method C) Applicable for sampling periods from one week to one year. The detection limit is 3 Bq/m3for an exposure period of one year and a counting area of 1.5 cm2.Methods for the determination of the concentrations of certain radon progeny, by membrane filter collection and measurement of alpha activity, and estimation of the total potential alpha energy concentration (PAEC) of radon progeny in indoor air are included in Appendix B. A sampling period of 5 min is used and, for the count intervals specified, this method should give a lower detection limit of 2.5 ¦ 10-8J/m3for the PAEC of the radon progeny.çNOTES:1 The recommended advisory level for radon in dwellings is expressed as a radon concentration in air, in becquerel per cubic metre, while actual radiation doses are calculated from the measurement of the concentration of the radon progeny in the air. The methods in Appendix B have been included for use in situations where measured radon concentrations are high enough to warrant further investigation.2 The detection limits for each method have been estimated using the procedure given by Currie (published in Analytical Chemistryº)

First published as AS 2365.4-1995.Reconfirmed 2014. First published as AS 2365.4-1995. Incorporating: Amdt 1-1996