The European Directive 2013/59/Euratom gave a deadline until February 8th, 2018 for the drafting of a national action plan needed for addressing long-term risks from radon exposure. However, it does not appear that the aforementioned national plan is in force.
This directive establishes two limits to buildings for the measurement of Radon gas over time:
Buildings of new construction: 200 Bq / m³
Existing buildings: 400 Bq / m³
However, the WHO recommends lower thresholds of maximum 100 Bq/m³.
The most common method of measuring radon gas is through direct indication monitors with short duration measurements. If a radon gas measured value above a reference is obtained, repeated measurements or measurements over a longer period of time are recommended.
Depending on the permeability and composition of the soil, radon content may vary considerably. There are locations that just need to be ventilated regularly and any fissure that may appear on floors or the basements covered with silicone.
In other cases, gas radon measurements show that other preventive measures need to be taken. Long-term measures are recommended before carrying out deep and expensive clean-ups. These write-offs may consist of construction or mechanical ventilation measures.