Protecting from radon levels in homes Developments for mapping radon prone areas can advance existing knowledge on the field, while actual mitigation techniques can provide relief for residents in radon-infected houses. Climate Change and Environment © PhotoDisc As people spend up to 90% of their time indoors in the recent years, the exposure to indoor environmental pollutants has become substantial with indoor air quality becoming poor. Concerns for exposure to radon, particularly, have increased, as this is considered a natural radioactive gas, causing human exposure to radiation. Such a context makes apparent the need for methods, which evaluate radon levels at homes, as well as mitigating techniques for exposure to the pollutant. As a first step, mapping radon sources in a large scale has been progressing, following measurements in a number of homes. Radon-prone areas have been mapped across the UK, at different scales. Mapping at 5 km resolution has been the norm, with 1 km resolution at areas where extensive measurements have taken place. A method has also been developed for transferring data on radon at homes, preserving geographic information in order to allow for correlation with geology, while also keeping the confidentiality of the results on radon. Measurements have also allowed for evaluation of the effectiveness of different radon mitigation techniques, in new homes, as well as at exiting houses. The most effective anti-radon measure has been found to be suspended concrete floors covered by a membrane across the whole floor area, with vents allowing sub-floor ventilation. In cases, where mitigation measures have been required after construction of the house with solid concrete floors, sub-floor sumps attached to extract fans were found to be effective. Suspended timber floors were found to be more problematic, and require provision of continuous flow of air across the sub-floor space. Finally, ventilation of indoor spaces, blowing air from the roof has also been found effective in reducing radon levels, whereas increase of under-floor ventilation by the simple addition of vents was tested to be unreliable.