Protocol for the Collection, Transfer and ANSI/AARST MW-RN 2020 Measurement of Radon in Water 37 hand, using a long-term electret for a water sample with a very low radon concentration may result in poor precision and agreement between detectors since the voltage drop is less precise. As such, if it is believed that the radon-in-water concentration is going to be low, better accuracy will be achieved by using a larger sample jar and a measurement period of 48 hours. 13.2 Analysis procedure–Electret method 13.2.1 Required procedure The required procedure to complete the measurement process and analysis, based on current methods, includes: 1) After at least 48 hours or as recommended by the manufacturer, remove the IEC device, close the air inlet to the ion chamber and record the time and date of the removal; 2) Measure and record the final electret voltage; and 3) Apply appropriate calculations supplied by the manufacturer to determine the reported measurement of radon in the water sample. 13.2.2 Vials Use of collection vials or containment jars of a volumes different than specified by the manufacturer shall include an adjustment in the calculations. Note—Details regarding method calculations are available elsewhere 5 or from the manufacturer. Calculations for the current method are based on: a) water samples collected in 68 mL (2.3 fl oz) or 136 mL (4.6 fluid oz) glass vials; and b) a containment jar capable of holding 3.75 L (1 gallon). 13.2.3 Bias Bias observed during successful participation in proficiency testing or laboratory intercomparison programs is to be corrected for when reporting measurements. Note—A negative experimental bias of 15% has been reported 6 when compared against liquid scintillation counting. SECTION 14.0 CONTINUOUS MONITOR (CRM) Informative advisory —The determination of radon in a water sample using a CRM often requires a somewhat larger sampling bottle, although the water collection techniques described above still apply. Since various proprietary analytical methods are available, users are referred to each manufacturer’s documentation. 14.1 Demonstration of proficiency CRM users shall successful participation in proficiency testing and/or laboratory intercomparison programs for radon in water, both initially and annually thereafter. 5 Kotrappa, P. and Jester, W.A. (1993) Electret Ion Chamber Radon Monitors Measure Dissolved 222Rn in Water, Health Physics 64:397-405. 6 Kitto, M.E., Fielman, E.M., Haines, D.K., Menia, T.A. and A. Bari (2008) Performance of a Commercial Radon-in- Water Measurement Kit, J. Environ. Radioact. 99, 1255-1257.