Quality Assurance & Quality Control
Introduction to Radon Mitigation
Worker Health & Safety
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Duplicate Measurements

These are made by exposing two or more detectors side by side to the same conditions to see how much they differ.  Duplicate measurements provide a way to estimate the reproducibility of measurement techniques and determine precision. The following table lists acceptable precision errors between duplicate (side-by-side) measurements for different devices:

Measurement Device  Precision Estimate
Charcoal canister    less than 10%
Continuous radon monitor    less than 10%
Electret ion chambers  less than 10%
Continuous WL monitor      less than 10%
Alpha track detectors   less than 20%, dependent on total area analyzed
Grab samples  less than 30%

The analysis of data from duplicates should follow the methodology outlined in EPA Radon & RDP Measurement Device Protocol, Goldin Section 5.3 1984/1992c. If the precision estimated by the user is not within the precision expected of the measurement method, the problem should be reported to the analysis laboratory and the cause investigated.