Effectiveness of Radon Mitigation Measures in 12 Houses 10 Years after Implementation

Abstract

Results are presented of radon concentrations in 12 houses 10 years after radon mitigation measures were implemented to reduce elevated radon concentrations in the houses. The houses were part of an earlier radon research project in which the home-owners received remediation advice from radon researchers, and a single contractor carried out the reduction measures. Remedia tion in nine of the houses was principally by installing an internal sump, in another by installing an external sump, in one by ventilating the crawl-space under the house, and one house had had a naturally ventilated sump sys tem built into the house and later had a fan installed to increase the sub-slab depressurization. The measure ments showed that ten years after radon reduction mea sures were implemented, only 3 of 12 houses had radon concentrations under the present-day action level of 200 Bq·m^-3 (5.4 pCi.1^-1) in Norway. The results suggest that radon levels should be measured at periodic inter vals after remediation, perhaps once every five years, to ensure that concentrations continue to be at acceptable levels.