Radon in workplaces

Origin, exposure and health effects

• Origin. Radioactive noble gas from the uranium decay chain in the ground; its concentration depends on the geology, soil permeability, building construction and ventilation.
• Entry points. Cracks and joints in slabs and walls in contact with the ground, installation passages, drains, basements and, to a lesser extent, construction materials and well water.
• Affected workplaces. Ground floors and basements of any activity in high potential areas, mines and tunnels, caves and tourist galleries, spas and resorts with groundwater, water treatment plants and underground parking lots.
• Health effects. Inhalation of radon and its decay products, which are deposited in the lungs and emit alpha radiation; it is the second leading cause of lung cancer and increases the risk in smokers.
• Reference level. 300 becquerels per cubic meter of average annual concentration, value from which corrective measures must be adopted.
• Variability. The concentration varies throughout the day and year, so measurements must be long-term and taken during periods of greatest accumulation.

Obligations of Royal Decree 1029/2022 and Instruction IS-47

The regulations require those responsible for workplaces located within priority municipalities, and for work activities with a risk of radon exposure (such as those carried out in underground facilities, spas, and water treatment plants), to have radon concentration measurements in the air taken by accredited laboratories, to integrate the results into the occupational risk assessment, to inform and consult with workers, and to implement measures to reduce the concentration below the reference level of 300 becquerels per cubic meter. If, after corrective measures, the average annual concentration continues to exceed the reference level, the operator must notify the Nuclear Safety Council, and the activity becomes subject to the radiological protection regime for exposed workers, including dose estimation, classification, monitoring, and registration.

The Nuclear Safety Council’s Instruction IS-47, published in 2025, approves the list of priority action municipalities (those classified as zone II in appendix B of section HS 6 of the Technical Building Code) and establishes the measurement guidelines in workplaces located on ground floors and basements of those municipalities: measurement for at least three months between October and May, or for a calendar year in quarterly periods, with a number of detectors proportional to the surface area and the distribution of the premises, a maximum period of six months after the opening of the center to start the measurements, and updating of the studies every five years, or every ten if the values ​​are less than 300 becquerels per cubic meter, and within six months after the works that affect the ventilation or the envelope.

Corrective and preventive measures

• Ventilation. Increase in natural or mechanical ventilation of the affected premises, with pressurization where possible.
• Sealing. Sealing of cracks, joints, installation passages and drains in slabs and walls in contact with the ground.
• Ground depressurization. Extraction systems under the slab or in sanitary chambers that evacuate radon before it enters the building.
• Barriers and design. Radon-resistant membranes and ventilated chambers in new construction and renovation in accordance with the Technical Building Code.
• Organization. Limiting the time spent in the most affected premises, relocating stalls and prohibiting smoking.
• Verification. Subsequent measurements to check the effectiveness of the measures and maintenance of the ventilation and extraction systems.

Organizational application: how to manage radon in the workplace

1. Check if the workplaces are located in municipalities of priority action according to Instruction IS-47 or if they carry out activities with a risk of exposure to radon, and identify the premises on ground floors and basements.
2. Contract the measurements with an accredited laboratory, with detectors in adequate number and location and during the required periods and durations, within six months after opening.
3. Integrate the results into the occupational risk assessment, inform and consult with workers and their representatives, and keep the documentation.
4. Apply corrective measures when the reference level is exceeded (ventilation, sealing, depressurization, reorganization) and repeat measurements to verify their effectiveness.
5. Notify the Nuclear Safety Council of the persistent exceedance of the reference level and apply, where appropriate, the radiological protection regime for exposed workers.
6. Update the studies every five years, or every ten if the values ​​are below the reference level, and in six months after works that affect ventilation or the building envelope.
7. Incorporate radon prevention into the design and rehabilitation of buildings in accordance with the Technical Building Code.

Preventive management software allows you to maintain the inventory of centers and premises subject to measurement, record laboratory results and corrective measures, schedule verification measurements and periodic updates with expiration notices, document information and consultation with workers, and maintain the traceability required by the regulations.

Limits and common mistakes

1. Assuming that radon only affects mines and tunnels and not checking the situation of centers in priority action municipalities.
2. Performing short-term measurements or measurements outside of the indicated periods, which do not represent the average annual concentration.
3. Measure only in some rooms and forget about basements, archives, warehouses and changing rooms on the ground floor.
4. Not integrating the results into the risk assessment or informing the workers.
5. Apply corrective measures without verifying their effectiveness with new measurements or maintaining ventilation systems.
6. Do not update studies after works that affect the building envelope or ventilation.

Specific requirements depend on the location of the center, the activity, and the current guidelines of the Nuclear Safety Council; this sheet is for informational purposes only.

Regulatory and reference framework

• Royal Decree 1029/2022, of December 20. Regulation on the protection of health against the risks arising from exposure to ionizing radiation; radon in workplaces.
• Instruction IS-47, of April 9, 2025, from the Nuclear Safety Council . List of municipalities with priority action against radon and guidelines for measurements in workplaces.
• Directive 2013/59/Euratom . Basic safety standards for protection against the dangers arising from exposure to ionizing radiation.
• Law 31/1995, of November 8. Law on the Prevention of Occupational Risks.
• Royal Decree 39/1997, of January 17. Regulation of Prevention Services; risk assessment.
• Nuclear Safety Council . Regulatory body for radiological protection; information on radon.

Section HS 6 of the Technical Building Code establishes the requirements for protection against radon in new buildings and in interventions in existing buildings, and its appendix B classifies the municipalities by zones.