radon is the second leading cause of lung cancer, after tobacco. In the Iberian Peninsula and across Europe, indoor radon exposure poses a significant public health risk, particularly in regions with granitic geology. Radon measurement in buildings is therefore a necessity — not just legal, but a matter of health — to ensure safe indoor environments. In this guide, we cover European legislation, measurement methods, professional equipment, and mitigation measures.
European and Iberian Legislation on Radon
The European framework for protection against ionising radiation, including radon, is based on Council Directive 2013/59/Euratom of 5 December 2013, which lays down basic safety standards for protection against the dangers arising from exposure to ionising radiation.Reference Level: 300 Bq/m³
The Directive establishes a reference level of 300 Bq/m³ for the annual average radon concentration in indoor air of existing buildings. Member States are required to transpose this into national legislation.National Transpositions
- Portugal — Decreto-Lei 108/2018: Transposes the Euratom Directive into Portuguese law, setting the 300 Bq/m³ reference level. Obligations include measurements in public buildings, workplaces, and new constructions, with focus on granitic risk zones in Northern and Central Portugal.
- Spain — Real Decreto 1029/2022: Spain’s transposition of the same Directive, also establishing the 300 Bq/m³ reference level and integrating radon prevention into the Technical Building Code (CTE).
Risk Zones in the Iberian Peninsula
The highest radon concentrations are found in regions with granitic geological substrates. In Portugal, this includes the districts of Braga, Vila Real, Viseu, Guarda, and Castelo Branco. In Spain, areas of Galicia, Castilla y León, Extremadura, and the Central System are most affected.How to Measure Radon
Radon measurement is the only reliable way to assess the concentration of this gas in a building. Concentrations vary significantly depending on local geology, building construction, ventilation, and season.Measurement Types
- Short-term measurement (2 to 7 days): Useful for rapid screening and preliminary assessments, but not representative of annual exposure. Results may be influenced by short-term weather conditions.
- Long-term measurement (3 to 12 months): The recommended method for obtaining the annual average concentration — the value comparable with the legislative reference level. Ideally, it should include the cold season, when windows are kept closed more often and indoor concentrations tend to be higher.
Measurement Methods
- Passive detectors (CR-39, LR-115): Devices that record alpha particles emitted by radon. They are cost-effective and suitable for long-term measurements but require subsequent laboratory analysis.
- Continuous electronic monitors: Instruments such as the SARAD range continuously measure and record radon concentration, enabling analysis of hourly and daily variations. Ideal for professional diagnostics and reference measurements.
- Activated charcoal: A short-term method (2-4 days) that adsorbs radon for subsequent laboratory measurement by gamma spectrometry.
Where and How to Place the Monitor
- Place on the lowest regularly occupied floor (basement, ground floor).
- Keep the detector in a room with normal usage conditions, with doors and windows closed as usual (not hermetically sealed).
- Avoid proximity to windows, exterior doors, heat sources, draughts, or excessive humidity.
- Recommended height: between 0.5 m and 2 m from the floor, away from walls.
Recommended Duration
For representative results, a minimum duration of 3 months is recommended, ideally during the cold season (October to March). A 12-month measurement covers all seasonal variations and is the most reliable for comparison with the reference level.SARAD Equipment for Radon Measurement
SARAD GmbH is a German manufacturer and a world leader in radon measurement instrumentation. Interphysix is the authorised SARAD distributor for the Iberian Peninsula.Radon Scout — Portable Continuous Monitors
The Radon Scout family is a range of compact, reliable continuous radon monitors suited to various applications:- Radon Scout PLUS — Continuous monitor for indoor measurements with hourly data logging of radon concentration, temperature, and humidity.
- Radon Scout Home — Designed for radon monitoring in residential spaces, with integrated display and configurable alarms.
- Radon Scout eXpert — Reference monitor for high-precision measurements, used in laboratories and calibrations.
- Radon Scout Everywhere — Monitor with LTE/LAN connectivity for remote and continuous monitoring, ideal for public buildings and monitoring networks.
- Radon Scout Professional — Radon dosimeter for extended measurements with expanded data memory.
DOSEman — Personal Radon Dosimeter
The DOSEman is a personal electronic dosimeter that measures individual radon exposure. Compact and portable, it is used by professionals working in environments with potential exposure — mines, basements, underground laboratories — to monitor and document cumulative personal dose.Thoron Scout — Radon and Thoron Measurement
The Thoron Scout simultaneously measures radon (Rn-222) and thoron (Rn-220) using two measurement chambers with different diffusion times. It is an essential instrument in contexts where thoron contributes significantly to exposure.Other Equipment
- RTM 2300 — Professional radon and thoron monitor with advanced measurement capabilities.
- Smart Radon Sensor — Intelligent radon sensor for integration with building automation systems (BMS/HVAC).
Mitigation Measures
When radon concentration in a building exceeds the reference level, mitigation measures must be adopted. The most appropriate strategy depends on the building type, the source of radon, and the measured concentration.Ventilation
- Natural ventilation: Regular opening of windows, especially on lower floors, can significantly reduce radon concentrations. However, it depends on occupant behaviour and weather conditions.
- Mechanical ventilation: Controlled mechanical ventilation (CMV) systems, with or without heat recovery, maintain constant air renewal independent of external conditions.
Sealing Cracks and Joints
Sealing cracks in the floor, joints between walls and slabs, and pipe/cable penetrations reduces radon entry points from the ground. While rarely sufficient as a standalone measure, it is an important complement.Sub-Slab Depressurisation Systems
Active sub-slab depressurisation is considered the most effective mitigation technique. It involves installing a suction point beneath the floor slab, connected to a fan that creates negative pressure under the building, preventing radon entry. Reductions of 80-99% in indoor concentration are frequently achieved.Radon Barriers in New Construction
In new construction, installing radon-impermeable membranes (radon barriers) beneath the foundation slab is an effective preventive measure at a relatively low cost when incorporated at the design stage.Frequently Asked Questions about Radon Measurement
Is radon dangerous? Yes. Radon is classified by the WHO and IARC (International Agency for Research on Cancer) as a Group 1 carcinogen. It is the second leading cause of lung cancer worldwide, after tobacco. How do I know if my building has radon? The only reliable way is through measurement. Radon is odourless, colourless, and tasteless, so it cannot be detected by human senses. Specific measurement instruments are required. What is the maximum permitted level? Both in Portugal (DL 108/2018) and Spain (RD 1029/2022), the reference level is 300 Bq/m³ for the annual average radon concentration in indoor air. This is consistent with the EU Directive 2013/59/Euratom. How long does a radon measurement take? It depends on the objective. A screening measurement can last 2 to 7 days. To obtain the annual average concentration — the value that is compared with the reference level — a minimum of 3 months is recommended, ideally including the cold season. Does Interphysix sell radon measurement equipment? Yes. Interphysix is the authorised SARAD distributor for the Iberian Peninsula and offers a complete range of professional radon measurement equipment, including continuous monitors, personal dosimeters, and sensors for building automation. Contact us for personalised advice.Need to measure radon in your building? Interphysix can help you choose the most suitable equipment for your needs. Contact us or browse our radon measurement equipment range.]]>
Última actualização: 09/04/2026