Update of Ireland's national average indoor radon concentration - Application of a new survey protocol.

In 2002, a National Radon Survey (NRS) in Ireland established that the geographically weighted national average indoor radon concentration was 89 Bq m-3. Since then a number of developments have taken place which are likely to have impacted on the national average radon level. Key among these was the introduction of amending Building Regulations in 1998 requiring radon preventive measures in new buildings in High Radon Areas (HRAs). In 2014, the Irish Government adopted the National Radon Control Strategy (NRCS) for Ireland. A knowledge gap identified in the NRCS was to update the national average for Ireland given the developments since 2002. The updated national average would also be used as a baseline metric to assess the effectiveness of the NRCS over time. A new national survey protocol was required that would measure radon in a sample of homes representative of radon risk and geographical location. The design of the survey protocol took into account that it is not feasible to repeat the 11,319 measurements carried out for the 2002 NRS due to time and resource constraints. However, the existence of that comprehensive survey allowed for a new protocol to be developed, involving measurements carried out in unbiased randomly selected volunteer homes. This paper sets out the development and application of that survey protocol. The results of the 2015 survey showed that the current national average indoor radon concentration for homes in Ireland is 77 Bq m-3, a decrease from the 89 Bq m-3 reported in the 2002 NRS. Analysis of the results by build date demonstrate that the introduction of the amending Building Regulations in 1998 have led to a reduction in the average indoor radon level in Ireland.