Accuracy and Precision of Home Radon Monitoring and the Effectiveness of EPA Monitoring Guidelines

EPA has provided guidelines to homeowners for monitoring and mitigating radon in the home. The effectiveness of these guidelines is dependent, in part, on the accuracy and precision of monitoring methods. This paper proposes a model for radon monitoring accuracy and precision based upon a review of the monitoring literature. The model is then used to quantify the extent of potential misclassification of homes by radon level from the application of EPA guidelines.

Short-term monitoring performed in the basement during winter produced conservative (higher than actual) radon estimates, on average. For homes with annual concentrations of 4 pCi/L, approximately 30 percent will still have short-term results under 4 pCi/L. Underestimation of radon levels is cut by 50 percent or more by the use of monitors on first floor and basement (confirmatory monitoring) as opposed to monitoring the basement alone (screening monitoring). However, following the screening/confirmatory monitoring sequence suggested by EPA increases underestimation at radon levels under 8 pCi/L. The model was found to be sensitive to a number of the assumptions made, and specific follow-up studies are suggested.