MS-QA_06-2019 rev5

ANSI/AARST MS-QA 2019 17 Radon Measurement Systems Quality Assurance Field Operations—EIC, Alpha Track and Charcoal Adsorption 5.3 Field Operations (EIC, ATD, CAD)—Required Spikes Spikes provide evidence of a continued accurate measurement system operation by comparing reported spike analyses results to a recognized reference authority for radon concentration. Documentation of within-limit spikes is necessary to support the validity of measurements. Spikes should be labeled and treated as other returned detectors and are not to be identified as spikes to the analyst. 5.3.1 Field Operations Spikes—Frequency and Procedures Users of CAD, ATD and EIC methods are responsible for setting aside at least 3% of the devices deployed for field measurements as spikes , arranging for and interpreting their results with six per month being the necessary maximum and no less than three per year. If using detectors of different configurations, even if from the same manufacturer, the same requirements apply for each different configuration, which includes both the design of the detector as well as the type and source of the charcoal or alpha track sensitive material. In addition, any project involving more than about 100 measurements shall include at least 3 spikes . 5.3.2 Field Operation Spikes (EIC, ATD, CAD)—Statistic Results of spikes are assessed using the statistic of RPE (also known as IPE; see Definitions), which represents the percentage by which each single measured value ( spike ) deviates from the chamber’s average concentration during the exposure period. 5.3.3 Field Operation Spikes—Warning and Control Limits Any single spike result exhibiting an RPE outside the range of 0 ± 20% has exceeded the warning limit, and any spike result outside the range of 0 ± 30% has exceeded the control limit. 5.4 Field Operations (EIC, ATD, CAD)—Required Duplicates Informative advisory —Deploying field duplicates provides evidence that field transport and handling procedures do not introduce unacceptable errors into the measurement system. These QC checks are very important because they can indicate changes in the system, differences between field operatives’ procedures or other contributors to imprecision that occurred during field operations. 5.4.1 Field Operation Duplicates—Frequency and Procedures Field operation duplicates are to be deployed in approximately one in 10 measurements, or 10% the time. Large projects involving more than 20 measurements are to include some duplicates . Conducting duplicates is to include exposing identical, collocated devices (see Definitions) simultaneously for at least 48 hours, submitting them for analysis without identification as duplicates ( blind ) and then comparing the two results. The results of each duplicate pair are to be recorded and plotted on control charts for evaluation. Field operation duplicates are to be distributed among different environments, operators and projects so that the duplicate data reflects the range of environments tested. Duplicates are to be deployed in environments greater than 4 pCi/L (150 Bq/m 3 ), when feasible, because the results from higher concentrations will provide more information for assessing and tracking precision error. 5.4.2 Field Operation Duplicates—Statistic The test statistic for duplicates is the RPD, which represents imprecision as a percentile of the best known concentration estimate. Note that the RPD is always positive, as the smaller measurement result is subtracted from the larger measurement result. The average of the two detectors is used in the denominator because the best estimate of the true concentration is the average of the results; the RPD therefore represents the imprecision as a percentage of the best true concentration estimate.