Residential radon remediation: performance over 17 years.

An exploratory radon measurement in 1990 identified 190 Bq m(-3) in the basement of a newly built home in Central New Jersey. Subsequently, the owner had a sub-slab remediation system installed in the basement, i.e. PVC duct through the basement floor connecting to an exhaust fan venting to the house roof. Sequential radon measurements began in 1992 using the NYU alpha-track detector. The homeowner wanted to insure the long-term durability of this remedial system. Seventeen years of measurements show the system functioned properly and reduced an established baseline concentration of 370 ± 8, 56 ± 1 and 67 ± 1 Bq m(-3) for the basement, first and second floors, respectively, to an average of 19 ± 4, 13 ± 3 and 10 ± 0.1 Bq m(-3). The last measurement, 2007-2008, with a newer NYU detector measured both (222)Rn (radon) and (220)Rn (thoron). The basement thoron concentration was 1.5 ± 0.9 Bq m(-3) or about 8 % of the (222)Rn value.