Regulation & authorities
Reference level
The radon concentration above which action to reduce exposure is considered warranted. The EU sets a maximum reference level of 300 Bq/m³ for homes and workplaces (Directive 2013/59/Euratom); the WHO recommends 100 Bq/m³ where feasible. It is not a strict safe/unsafe boundary — risk exists at any level.
Related terms
Action levelThe term used by the US EPA for the concentration at which it recommends fixing a building: 4 pCi/L (about 148 Bq/m³). The EPA also suggests considering mitigation between 2 and 4 pCi/L.Directive 2013/59/EuratomThe EU Basic Safety Standards Directive that obliges member states to establish a national radon action plan, set reference levels not exceeding 300 Bq/m³ for dwellings and workplaces, identify radon priority areas and regulate radon in workplaces and new buildings.Radon priority areaAn area officially designated by a national authority where a significant share of buildings is expected to exceed the reference level. Designation typically triggers obligations such as workplace measurements and radon protection in new construction.CTE DB-HS6 (Spain)The section of the Spanish Building Code (Código Técnico de la Edificación, Documento Básico HS6) that regulates protection against radon in buildings. It lists the municipalities where protective measures are required and sets a reference level of 300 Bq/m³.CSN (Consejo de Seguridad Nuclear)Spain’s nuclear safety and radiation protection regulator. Regarding radon, it publishes the national radon potential cartography, participates in the national radon action plan and issues guidance for measurement and mitigation.