Estimation of seasonal correction factors through Fourier decomposition analysis--a new model for indoor radon levels in Irish homes.

Radon concentrations in homes have been shown to vary considerably with season. It is important to account for this by applying a correction factor to any home radon measurement of less than one year. To date, Irish radon measurement services have used correction factors based on data derived for the UK in the 1980s. In the absence of similar data for Ireland at the time, these were considered suitable for use due to the similarities between the climates, house types and lifestyles in the two countries. In order to better estimate the long-term radon concentration, measurements from 5640 Irish homes were used to derive a set of correction factors specifically for Ireland. These were generated by means of Fourier decomposition analysis and the new correction factors compared, using 95% confidence intervals, to those derived for the UK using the same analysis and to those currently in use for Ireland. In both cases, a significant difference was found between 10 of the 12 monthly seasonal correction factors. This paper presents the methods used in detail and the results of the analysis.

The effectiveness of radon remediation in Irish schools.

An advisory reference level of 200 Bq m(-3) and a statutory reference level of 400 Bq m(-3) apply to radon exposure in Irish schools. Following the results of a national survey of radon in Irish schools, several hundred classrooms were identified in which the reference levels were exceeded and a remediation program was put in place. This paper provides an initial analysis of the effectiveness of that remediation program. All remediation techniques proved successful in reducing radon concentrations. Active systems such as radon sumps and fan assisted under-floor ventilation were generally applied in rooms with radon concentrations above 400 Bq m(-3). These proved most effective with average radon reduction factors of 9 to 34 being achieved for radon sumps and 13 to 57 for fan assisted under-floor ventilation. Both of these techniques achieved maximum radon reduction factors in excess of 100. The highest average reduction factors were associated with the highest initial radon concentrations. Passive remediation systems such as wall and window vents were used to increase background ventilation in rooms with radon concentrations below 400 Bq m(-3) and achieved average radon reductions of approximately 55%. Following the installation of active remediation systems, the radon concentration in adjacent rooms, i.e., rooms in which the radon concentration was already below 200 Bq m(-3) and therefore did not require remediation, was further reduced by an average of 25%. The long-term effectiveness of a number of radon sump systems with at least three years operation showed no evidence of fan failures. This study showed an apparent increase in sump effectiveness with time as indicated by an increase in radon reduction factors during this period.