Underground Air Returns as Active Transportation Pathways for Radon Gas Entry into Homes
K. J. Kearfott, R. L. Metzger, K. E. Holbert
Levels of elevated Rn-222 in homes can fail to correlate with measured radium concentrations in soils and surrounding rocks for reasons which can include water sources, building materials, and unusual variations in climate or building construction. Several homes were identified in the Phoenix, AZ metropolitan area with soil radium concentrations of <0.074 Bq/g (2.0 pCi/g) which had elevated radon concentrations unexplained by geological sources alone. Continuous monitoring of eight houses under different conditions of cooling system usage revealed a definite role of the underground air returns as active transport pathways contributing to the enhancement of the indoor concentration of Rn-222 in six of the houses. The ratio of indoor Rn-222 concentrations on days when the cooling system was operated continuously compared to days the system was off ranged from essentially one up to a factor exceeding 10.
Health Physics, Vol. 63, No. 6, pp. 665-673, 1992.
Mitigation of Elevated Indoor Radon Gas Resulting from Underground Air Return Usage
K. J. Kearfott, R. L. Metzger, K. R. Kraft, K. E. Holbert
Underground air returns have been found to be active transportation pathways for radon gas entry into homes. Several homes for which underground air returns were contributing to elevated indoor Rn-222 concentrations were evaluated for possible mitigation. Two houses with such problems were successfully mitigated by inserting flexible ducts into the returns. In one of these houses, the initial mitigation attempt resulted in an exacerbation of the problem due to the leakage of the ducting. This was solved by re-sleeving the returns using a stronger material. Mitigation of elevated indoor radon gas caused by use of underground air returns by inserting flexible ducts is not possible for all situations, especially those for which the returns are small, filled with debris, misaligned, or inaccessible.
Health Physics, Vol. 63, No. 6, pp. 674-680, 1992.