5.1 The most prevalent of the radon isotopes in ground water is ²²²Rn. This isotope presents the greatest health risk compared to the other naturally occurring radon isotopes if ingested via the water pathway.

1.1 This test method covers the measurement of radon in drinking water in concentrations above 2 Bq/L.

1.2 This test method may be used for absolute measurements by calibrating with a ²²⁶Ra standard or for relative measurements by comparing the measurements made with each other.

1.3 This test method is used successfully with drinking water samples and Type III reagent water conforming to Specification D1193. It is the user’s responsibility to ensure the validity of this test method for waters of untested matrices.

1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.5 This standard does not purport to address the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.