Winnipeg radon testing: comparison of test durations, effects of house characteristics, and efficacy of floor-drain seals.

A research study has investigated the correlation of radon test data for three testing periods obtained in a set of 50 homes. The homes were part of the housing stock in a long-established subdivision in Winnipeg, Manitoba, for which it was initially hypothesized that a high percentage of homes had radon levels above the Canadian guideline. Co-linear tests, all commencing on the same date, were conducted over periods of 5 d, 30 d, and 91 d under closed building conditions during the 2009-10 heating season using electret ion radon detectors, supplemented in some instances by measurements with a continuous radon monitor. Radon levels in 33 of the 50 homes exceeded the Canadian radon guideline of 200 Bq m in 91-d tests. False-positive and false-negative analyses of the 5-d tests and 30-d tests were conducted relative to the 91-d tests in the respective homes. False positive/false negative analyses indicated that the short-term and the medium-term testing results reflected the results of the 91-d tests over 85% of the time. Precision testing of the radon data was carried out in accordance with quality assurance protocols. Correlation of a building construction survey with radon data indicated that earth-floor crawl spaces were common contributors to elevated radon levels. Testing was also done to measure the efficacy of a commercial brand of floor drain seal installed to lower radon levels, which resulted in an average radon reduction of 47% in homes without earth-floor crawl spaces.