Radon map of Spain, town by town

Radon is a natural radioactive gas that rises from some ground, granite above all, and builds up inside homes. Spain's Building Code (DB HS 6) lists 4,043 towns where homes need protection: 1,644 in zone II and 2,399 in zone I.

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What it requires

• Zone I: a radon barrier under the house, or a ventilated space or ground depressurisation.
• Zone II: the barrier and, as well, a ventilated space or ground depressurisation.

It applies to new homes and to many works on existing ones, such as extensions, changes of use and restorations. The reference level is 300 Bq/m³ as a yearly average; a measurement with detectors costs little and gives each house its answer.

Provinces with the most zone II towns

The town finder filters towns outside radon zones, and each town's page gives its zone.

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Source: Código Técnico de la Edificación, DB HS 6 (protection against radon), appendix B.