Radon in the workplace

What radon is

Radon is a radioactive gas – it is a hazard in many homes and workplaces. We can't see, smell or taste it and you need special equipment to detect it. It comes from the rocks and soil found everywhere in the UK. The radon level in the air we breathe outside is very low but can be higher inside buildings.

Breathing in radon is the second largest cause of lung cancer in the UK, resulting in over 1000 fatal cancers per year.

Radon hazards are simple and cheap to measure and relatively easy to address if levels are high. Under UK regulations, all employers must review the potential radon hazard in their premises.

You can find detailed guidance about radon for employers from UK radon. It covers:

  • more information on what radon is
  • maps of radone-prone areas in the UK
  • a breakdown of types of radiation dose
  • services including radon address search and measurement kits
  • methods of reducing radon levels, including sumps

Radon in the workplace

Excessive levels of radon gas can occur in almost any type of workplace. The amount of radon that collects in a building depends on its location, structure and how it is used.

In workplaces such as offices, where hazards are normally low, radon can be the largest occupational health risk.

Employees who live nearby may also be exposed to a high radon level while at home. Wider awareness of radon can, therefore, benefit your workers. There is more information on domestic radon exposure of employees.

Workplaces which may be affected

The UK Health Security Agency has published a map showing where high levels are more likely. This was created by combining the results of measurements in houses with maps of the underlying geology. Locations with elevated radon potential are called 'affected areas'.

Employers and householders may consult the definitive dataset on the UK radon website to see if their premises are in one of these areas (a small fee is charged).

The 'indicative map', which shows the worst-case radon potential for each 1 km grid square, is freely available on the UK radon website.

All workplaces in radon radon affected areas should be tested, unless a detailed assessment shows good reason to expect the radon level to be low.

Search services are available to help you find out if premises are in an affected area and anyone not sure about which search to use can contact UK radon.

All types of indoor workplace including factories, warehouses, offices, shops, schools, hotels, nursing homes, residential care homes and health centres can have high radon levels.

Underground workplaces such as basements, cellars, mines, caves and utility industry service ducts can have significant levels of radon as can any above-ground workplaces, mainly in radon affected areas.

Employers who only occupy parts of buildings from the first floor and above are less likely to have significant radon levels than those on the ground floor or below.

You can find more information about radon in the workplace from UK radon.

Legal requirements for workplaces – risk assessment

Although the radon data used in production of the  indicative map of radon affected areas comes from measurements in homes, the maps indicate the likely extent of the local radon hazard in all buildings.

The information in the indicative map is therefore relevant to employers in assessing workplace risks.

Under the Health and Safety at Work Act, employers must, so far as is reasonably practicable, ensure the health and safety of employees and others who have access to their work environment.

The Management of Health and Safety at Work Regulations require the assessment of health and safety risks and this should include radon in the following circumstances.

Workplaces above ground

For the vast majority of workplaces above ground the risk assessment should include radon measurements in appropriate ground floor rooms where the building is located in a radon affected area.

Employers may choose to take a conservative approach and carry out measurements in all premises located in a 1-km grid square that is shaded in the indicative map of radon affected areas (measurements are not usually required in workplaces that are above ground and located in the white areas of the indicative map).

If employers wish to be more specific they may choose to consult the definitive radon dataset online (a small fee is charged) to identify the affected area status of a particular building or buildings.

Workplaces below ground

For occupied workplaces below ground the risk assessment should include radon measurements. These workplaces could include:

  • those occupied for more than an average of an hour per week or approximately 50 hours per year, or
  • those containing an open water source

This applies to all workplaces below ground in the UK (basements, cellars, mines, caves, tunnels etc), irrespective of the above-ground affected areas status.

The Ionising Radiations Regulations 2017

The Ionising Radiations Regulations 2017 (IRR17) come into effect where:

  • radon is present above the defined level of 300 Bq/m3 (as an annual average), and
  • employers are required to take action to restrict resulting exposures

HSE and local authorities are responsible for enforcing these Regulations in particular types of workplace.

Testing for radon

Radon surveys should be conducted in any workplace where its location and characteristics suggest that:

  • elevated levels may be found
  • significant exposures to employees and/or other people are possible

Inexpensive surveys can be carried out by leaving small plastic passive detectors in rooms or occupied locations of interest.

The UK radon website contains up-to-date details of validated laboratories capable of supplying such detectors for carrying out radon measurements. Delivery and return of the dosemeters is usually by post.

Supported by Building Research Establishment report BR211, the following regulations describe where new buildings and extensions (workplaces and dwellings) might need to incorporate protective measures installed during construction:

Since even new buildings with protective measures may have high radon levels, employers must still test as described above.

Experience has shown that radon concentrations in adjacent buildings, even adjoining ones, can differ greatly (for reasons including local geology, building design and usage). Measurement results from neighbouring properties cannot therefore be used in the risk assessment.

What test results will mean

For levels below 300 Bq/m3

Where the workplace measurements show annual average radon levels below 300 Bq/m3, as is the case for the majority of employers, the only further action required is to decide when the risk assessment will be reviewed.

Levels above 300 Bq/m3

For occupied areas with levels above 300 Bq/m3, the employer may need to immediately take steps to manage occupational exposures pending any decision they may take to reduce the radon levels by engineered means.

Consulting a radiation protection adviser

A radiation protection adviser (RPA) with radon experience should normally be consulted about how best to manage radon exposures. However, if the employer plans to introduce engineering controls to immediately reduce the radon exposures, they will also need to consult a specialist radon removal (remediation) contractor.

The specialist will be able to advise on the most cost-effective engineered means of reducing radon levels. It is usually appropriate to continue monitoring in these areas at least until the reduction measures have been put in place, or to refine where the highest radon levels are located by monitoring additional rooms.

Assessing average annual levels

The seasonal adjustments applied by testing laboratories to measurements are normally good indicators of the annual average levels in buildings.

It is good practice to consider methods of restricting the radon exposures immediately if the seasonally adjusted figures are significantly greater than 300 Bq/m3 and not wait for further measurements, as this would result in additional radiation doses to people in those premises.

Practical control of radon levels in buildings

Radon enters a building primarily by airflow from the underlying ground. Protection measures for reducing levels inside workplaces vary depending on the severity of the problem and the type of building construction.

New buildings can be protected during construction by installing a 'radon proof' barrier or membrane within the floor structure and, in areas with a greater radon potential, provision of a ventilated sub-floor void or a 'radon sump'.

A radon sump is a small, bucket-sized, cavity under the floor with an electric pump drawing air from it. This reduces the normal under floor pressure with respect to radon in the soil and vents the radon gas outside the building where it quickly dissipates.

In existing buildings, it is not possible to provide a radon proof barrier, so alternative reduction measures are used depending upon the radon level. Such measures include:

  • improved under floor and indoor ventilation in the area
  • sealing large gaps in floors and walls in contact with the ground
  • positive ventilation of occupied areas
  • installation of radon sumps and extraction pipework

You can find descriptions of radon solutions on the BRE website.

There is also advice on how to reduce radon levels on the UK radon website.

If it is necessary to reduce radon levels by engineered means, the employer should ensure the radon levels in the area are remeasured immediately after installation in to verify its effectiveness. Regular maintenance of the engineering controls, supported by occasional (for example annual) measurements will ensure the system remains effective.

Practical control of radon levels underground

Controlling radon in underground workplaces such as mines, caves and tunnels may need the specialist advice of a ventilation or mining engineer.

The employer may need further radon measurements to determine the seasonal variations, as radon levels underground can be considerably higher in the summer months than during the winter and affected by changing water levels.

Reviewing radon risk assessments

As with all health and safety risk assessments, their applicability should be kept under review. Where significant changes are made to the fabric of a building or to the work processes carried out within it, then the need to remeasure the radon levels should be considered.

In any case, it is still good practice to assign a maximum period upon which remeasurement of the radon levels will occur. While the employer is best placed to determine the frequency of any remeasurements, in consultation with the radiation protection adviser where appropriate, HSE suggests the following guidelines:

  • where radon levels were found to be significantly less than 300 Bq/m3 at the initial measurement, the period of remeasurement might be approximately once every 10 years
  • where radon levels were just below 300 Bq/m3 at the initial measurement, the suggested period for remeasurement will be less than 10 years
  • where radon levels were above 300 Bq/m3 at the initial measurement and measures have been taken to reduce radon exposures (such as engineered systems or occupancy restrictions), the remeasurement periods may need to be significantly more frequent to verify their continuing effectiveness

Domestic radon exposure of employees

In radon-affected areas employees could also be receiving significant radon exposure at home.

Employers are strongly encouraged to recommend home testing to their employees who live in a radon-affected area. Measurement laboratories provide radon home measurement packs. They charge per house and tenants should contact their landlords to arrange testing.

Further information

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Updated 2025-02-03