RRNC 2020 Companion Guidance Section C: Understanding ASD CG 3 Companion Guidance Section C Understanding Active Soil Depressurization (Builders and Code Officials) Radon : Radon is a colorless, odorless, radioactive gas that occurs naturally in all parts of the US. Radon is a “Group A” carcinogen and is the second leading cause of lung cancer after smoking and the leading cause of lung cancer in non-smokers. The EPA estimates that radon is responsible for the death of about 21,000 people in the United States every year. Radon concentrations are reported in picoCuries per liter ( pCi/L ) or in Becquerels per cubic meter [Bq/m3], which is a measure of radioactivity in a volume of air. The only way to determine the concentration of radon in a home is to perform a test. Radon Potential: The EPA Zone Map provides a county by county potential for indoor radon concentrations across the United States. Zone 1 counties have a predicted average indoor radon screening level greater than 4 pCi/L [148 Bq/m 3 ]. Zone 2 indicates a Moderate Potential for radon and Zone 3 is the lowest radon potential area. The World Health Organization (WHO) reference level is 2.7 pCi/L [100 Bq/m 3 ] and the WHO recommends that action be taken to reduce occupant radon exposure to below this reference level. Your State may provide more detailed radon maps; check with your State radon or local Building Inspector office. Radon Potential of a Building Lot: County by county radon potential mapping may predict average screening levels, however, the radon potential of any given building lot is dependent on the local conditions which determine whether source material is available in the soil and whether there is sufficient pathway and driving force to create a radon problem in any given dwelling . There are no nationally recognized protocols for radon testing of building lots and soil testing a building lot for radon potential has not been demonstrated to reliably predict final indoor radon concentrations. Therefore, an Active Soil Depressurization ( ASD ) System installation may be preferred during initial construction. The alternative is the Rough-In system approach that if necessary, could be later activated after completion of construction. Radon Testing: Testing for radon can be performed with a number of different testing methods, including charcoal canister, liquid scintillation, electret, alpha track or continuous radon monitor. Short-term testing must be performed under “Closed-building Conditions” which means that the building must be near completion with all doors and windows closed (except for normal entry and exit). The building should also be heated/cooled and construction activities should be minimal during the testing period.