Work environments vary greatly in size and nature, but 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. Furthermore, employees who live nearby may also be exposed to a high radon level while at home. Wider awareness of radon can, therefore, benefit your staff.

All workplaces in 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 find out if premises are in an Affected Area and anyone not sure about which search to use can contact us.

Radon comes from the ground and underground areas are more likely to have high radon levels. Therefore, any frequently occupied basements should also be tested, regardless of whether or not the site is in an Affected Area. Specialist advice should be sought for wholly underground workplaces such as mines, tunnels and caves and if there are internal sources of radon such as geological samples.

Once inside a building, the level of radon depends on the amount of ventilation and the nature of the work. Radon levels can vary greatly within a large building and individual risk depends on the radon level in the different areas where staff spend most of their time. It is important to measure the radon levels in areas that represent the different working environments in the building.

A simple test pack for radon can be ordered through this website. Testing is generally undertaken in ground floor rooms that are used routinely. Other rooms, on higher floors or those in which people spend little time, do not generally need to be tested. If you are not sure how many detectors you need, follow the guide below.


Workplace type* Number of monitors Examples
Office, individual or small One per 100 m2, generally corresponds to between a half and third of all ground floor rooms Banks, small shops, professional practice (solicitors, etc), residential homes, schools
Open plan office, and retail or workshop up to about 1000 m2, also public access areas One per 250 m2 Administrative and call centres, light industry, hotels
As above, up to 5000 m2 One per 500 m2 Large retail etc
Very large areas of several thousand m2 One for each distinct area with obviously different environmental conditions, not less than 1 per 1000 m2. Manufacturing or process plant, warehouses
Basements Should be monitored if occupied for more than 50 hours per year

(~ an hour per week). One monitor for each occupied room, section or area. Basements with generally high occupancy should be monitored using the rules as for ground floors

Retail, bank and professional storage areas
Wholly underground As a guide at least one in each main working area, and other normally occupied areas, but seek specialist advice Water industry, mines and caves

* Effect of ventilation - In principle, radon may be prevented from accumulating in premises with particularly high influx of fresh air, but a measurement is still required unless a risk assessment can show that the radon level at a particular location is necessarily low at all times when it is occupied. Furthermore there will often be adjoining or linked places, such as an office, store, computer area or access duct, with quite different conditions where a measurement would be required.


If you have a large number of premises to test, consider how you are going to manage the logistics.

If a radon level in any part of a workplace exceeds 300 Becquerels per cubic metre (Bq m-3) as an annual average, the Regulations covering ionising radiations apply. The employer is then obliged to take action. Radon measurement reports from UKHSA include advice to guide employers on the actions they can take to protect staff.

Radon levels can vary over time. This is usually because of changes to the construction of the building or alterations to heating and ventilation which can be caused by a change in use. For this reason, radon should remain in your routine reviews of risk assessments. Consider any changes and assess whether or not the test needs to be repeated. If a radon reduction system has been installed to reduce high levels, those systems may also fail over time and radon levels should be checked annually.

Dealing with the possibility of high radon levels in your workplace may seem daunting. However, there is a basic process which if followed, will help you successfully manage the risk of radon in your workplace:

  • Assess the risk of having a high radon level
  • Measure the radon levels in the premises with a higher risk
  • Act on any high results
  • Monitor any changes to the premise or its use and assess the need to retest. Check any radon reduction systems.