New indoor radon mitigation guides in Finland

摘要

Radiation and Nuclear Safety Authority - STUK and the Ministry of Environment have published in spring 2008 two new Finnish indoor radon mitigation guides. Both guides are revisions from previous 1990's issues. The first guide published by STUK gives basic information about all mitigation methods used in Finland. The most efficient method are sub-slab depressurization (SSD) and radon well, typical radon concentration reduction factors being 70-90percent for both methods. The guide gives detailed information with many examples for SSD and radon well design and implementation. Sealing entry routes resulted normally in reduction factors of 10 - 40percent. Complete sealing may be requiring and expensive. Improving ventilation resulted only in few cases a reduction factor higher than 50percent. Installing of fresh air vents in some cases decreases the depressure level of the house and the inflow of radon bearing soil air. Installation of SSD, radon well or fresh air vents are the most effective measures in blocks of flats. The guide handles briefly also radon mitigation in workplaces and big buildings. The second guide published by the Ministry of Environment is a detailed guide for design and implementation of a SSD in low rise residential houses. Practical information choosing the location of suction pit, implementation of suction pit and system piping has been given. The STUK-guide will be published also in Swedish.