Protocol for the Collection, Transfer and ANSI/AARST MW-RN 2020 Measurement of Radon in Water 8 SECTION 5.0 FIELD OPERATIONS—SAMPLE COLLECTION Informative advisory —It is critical to avoid any water that is collected in the sample container from coming in contact with air. As the solubility of radon is greater in air, exposure of the water sample to air can result in a loss of radon and a falsely low result. There are two EPA-recommended methods 3 for collection of a representative water sample that involve no contact of the water with air and likely provide a more accurate result, as opposed to collection methods that allow a slight contact of the water sample with air. While gloves are not required for collecting water samples to measure radon, clean hands are recommended. 5.1 Collection methods 5.1.1 All water samples shall be collected using only the methods described herein, or as approved by a state or nationally-recognized certification program. 5.1.2 A hose greater than ½ ” (1.25 cm) diameter and longer than 24” (60 cm) shall not be used. 5.1.3 Sample bottles shall not be filled directly from or in contact with the faucet spigot. 5.2 Take the sample(s) immediately after flushing water lines or holding tanks The sample(s) shall be collected immediately following the purging of water from piping and tanks in accordance with Section 4 . 5.3 Duplicate samples required All water samples for radon determination shall be collected in duplicate . Note—Collection (and analysis) of duplicate samples serves to: a) confirm results for decisions regarding mitigation; and b) provide a QC check of the reproducibility regarding the collection, transfer, and analysis methods. 5.3.1 If a single sample was collected In the event only a single sample was collected or for unforeseen circumstances one is found suitable for analysis and the concentration is below 20,000 pCi/L (740 Bq/L), a sequential sample shall be collected within 2 weeks of the initial sampling. Flushing of the water line shall be identical each time. Sequential sampling shall be documented with the date and time of collection for both water samples. Both individual results and an average shall be reported unless State guidance differs. Note—While decisions to mitigate are not prohibited at any time, comprehensive testing provides confidence that decisions are not being made based on inconclusive or inconsistent collections or measurements. 5.4 Visible bubbles in the sample After closing sample collection bottles, the bottle shall be inspected to ensure there are no bubbles larger than 1-mm (1/16”) diameter. If a bubble larger than 1-mm (1/16”) diameter exists in the bottle, the water from the sample bottle shall be discarded and the collection procedure repeated. 3 Whittaker, E.L., Akridge, J.D., Giovano, J. (1989) Two Test Procedures for Radon in Drinking Water: Interlaboratory Collaborative Study. U.S. EPA Environmental Monitoring Systems Laboratory, Las Vegas, NV. EPA 600/2-87/082.