Occupational exposure to radon in workplace buildings

OC 560/50

This 2-part OC revises and replaces OC 560/20(REV). It provides a brief description of radon and its associated hazards; the Management of Health & Safety at Work Regulations 1999 requirements for assessment of the risks in workplaces in specified geographical locations, information on the application of the Ionising Radiations Regulations (IRR99) (file 560) to work in radon-affected workplaces, some appropriate control measures and advice on enforcement. The main differences between this OC and OC 560/20(REV) are described in para 1. The Information Document (ID) may be copied to interested persons outside HSE.



1 This revised OC introduces updated information on radon-222 (referred to as radon throughout this document) in workplaces. The main differences between this OC and OC 560/20(rev) relate to the application of new legislation to occupational radon exposure (in particular, the need for a suitable risk assessment, and requirements for consultation and appointment of radiation protection advisers (RPAs)). Updated information on radon measurement and details of contacts for further advice are included. The new ID is a working document for inspectors but may also be copied to interested people outside HSE. It gives useful advice on where radon problems are likely to exist and how to deal with them. Published external guidance for dutyholders is also planned.

2 Although exposure to radon is a complex problem, its restriction is often easily achieved. Simple remedial action by dutyholders can contribute to a significant reduction in UK occupational exposures to ionising radiation from this source.

3 Radioactive decay of naturally occurring uranium and thorium in rocks leads to the formation of the radioactive gas radon. This can escape from the rock via pores and cracks to reach the surface. It may then collect in buildings and under certain conditions can reach concentrations above which the risk to people in the workplace requires control under the Ionising Radiations Regulations 1999. Radon is odourless, tasteless and colourless and can only be detected using specialised equipment. Radon is now recognised to be the second largest cause of lung cancer in the UK after smoking. It is estimated that radon causes 2000 to 3000 lung cancer fatalities in the UK every year and in certain areas a significant proportion of an employee/s daily exposure may occur at work.

4 Exposure to radon in homes falls within the responsibility of the Department for Environment, Food and Rural Affairs (DEFRA) in England, the Welsh Assembly in Wales and the Scottish Executive in Scotland. An extensive programme to raise the awareness of homeowners, undertake measurements of domestic radon levels and implement appropriate remedial measures began in 2000 (in association with local authorities in radon-affected areas).

5 The ID gives guidance on the origin and characteristics of radon, together with the likely style and location of buildings where elevated levels may be found. It gives brief details of how initial surveys should be conducted and outlines remedial measures that can be taken.


6 This OC addresses the general situation of work in a radon atmosphere where radon enters the workplace from the ground.

7 IRR99 reg.3(1)(b) states that the Regulations apply to work 'carried out in an atmosphere containing radon 222 gas at a concentration in air exceeding 400 Bqm-3. [Radon gas air activity concentration is measured in Becquerels per cubic metre, Bqm-3.] In a small number of cases, the Regulations can be disapplied if the employer can show that the second threshold in regulation 3(1)(b) has not been exceeded.

8 The best way in which employers can deal with radon in the workplace is to reduce levels to below that at which IRR99 apply. They can usually do this using the relatively simple engineering methods discussed in the ID. Such systems should be subject to appropriate planned preventative maintenance and testing under general requirements of health and safety legislation, as with other workplace equipment.

9 If such measures do not reduce the levels sufficiently (ie to below 400 Bqm-3), then IRR99 apply as for any other occupational exposure to ionising radiation. So:

(1) work should be notified to HSE (reg.6);

(2) a prior risk assessment should be undertaken (reg.7); and

(3) exposures of persons must be restricted so far as is reasonably practicable (the ALARP principle) (reg.8) using, in order of preference:

(a) engineering controls;

(b) installed safety features;

(c) appropriate systems of work, provision of information, instruction and training to employees; and, where necessary;

(d) appropriate PPE.

10 Where levels above 400 Bqm-3exist, it is good practice as part of personal exposure management to designate a supervised area (reg 16(3). Part of the supervision will involve controls of occupancy times in the area and ensuring that installed safety features and engineering controls used to restrict exposures are subject to a suitable schedule of maintenance and testing (reg.10).

11 Areas where levels of radon (or radon daughters, which are the decay products of radon that are solid and radioactive (see para 4 of the ID)) are sufficiently high to require special procedures to restrict exposures, or where people working might receive an effective dose greater than 6mSv per year, must be designated as controlled areas (reg.16). Consequently, local rules must be provided for entry into those areas and one or more radiation protection supervisors appointed (reg.17). Employers must ensure that such areas are physically demarcated or delineated with appropriate signs and that access into the area is restricted (reg.18).

12 Very few employers are likely to have employees who will require to be designated as classified workers (reg.20) because, in most cases, it will be reasonably practicable to restrict access to areas where radon levels are significant (reg.8). However, a few employers, eg operators of deep mines, do have a number of classified employees and, in these cases, appropriate dosimetry from an approved dosimetry service and medical surveillance are required (regs.20-24).

Consultation with radiation protection advisers

13 The IRR99 require employers in certain circumstances to consult a radiation protection adviser (RPA) for advice on compliance with those Regulations. Employers who seek to establish whether IRR99 apply as a result of radon levels in their workplace do not need to consult an RPA until they have first established whether they apply. Usually this will be done by employers obtaining measurements of the levels of radon in their workplace. If the level is below 400 Bq m-3, then nothing further needs to be done other than to confirm this at appropriate intervals. Employers will need to ensure that further measurements are undertaken should any modifications to the building be carried out, or if there is a change in the circumstances of the work. If the measured levels are above 400 Bq m-3the employer has two options, either to:

(1) remove the radon from the workplace through remediation so that IRR99 do not apply (para 9). In this case, employers are not required to consult an RPA; or

(2) manage the exposures that arise from working in the affected areas (paras 10 - 13). Full consultation with an RPA is thus required (reg.13 IRR99).


14 If the geographical location (see para 6 of the ID) and the type of building (see para 7 of the ID) lead inspectors to believe that there could be a risk of significant exposure arising from radon, then they should question relevant employers to see if they know the scale of the problem and have taken measures to address it. In radon-affected areas (see Figure 2 in the attached ID) inspectors can require employers, using the Management of Health and Safety at Work Regulations, regulation 3 (MHSWR), to undertaken an initial assessment to determine whether there may be a radon hazard within their workplace (including cellars and basements). It is recommended that inspectors should require employers to undertake risk assessments in those areas of the map at Figure 2 where the estimated percentage of houses above the domestic action level is greater than one percent.

15 Basic measurement of radon concentration can be undertaken for around 50 (at 2002 prices) using simple, robust and unobtrusive detectors which are left at the premises for a few months and then sent back to the supplier for analysis. The results of this measurement will indicate whether more detailed measurement is necessary, which might in turn indicate the need for appropriate control measures as discussed in the ID. A list of laboratories providing radon dosemeters and measurement services is included in the ID.

16 When questioning management regarding their assessment of the risks, inspectors may find it useful to provide the employer with a copy of the current HSE employer guidance 'Radon in the Workplace' IND(G)210L together with a photocopy of the attached ID. Inspectors should require employers to report the results of the risk assessment to HSE, a period of approximately five months should be allowed, to enable the three-month measurements, etc to be carried out.

17 Note : Measurement of radon concentration is subject to a number of uncertainties, eg variations with time of day or time of year. Radon sampling can be carried out using a variety of devices, and interpretation of survey results requires considerable experience and expertise. Inspectors should not take further enforcement action based on survey results without first consulting a specialist group radiation inspector.

Focus recording

18 Contact entries against the incumbent should be along the lines of one of these below:

(i) Radon discussed Measurements to be undertaken and results forwarded to me by ../../..

(ii) Radon discussed. Employer refuses to undertake measurements. IN issued for measurements to be undertaken and results forwarded to me by ../../..

(iii) Radon discussed. Measurements have been undertaken (max xxx Bqm-3) and no remediation measures necessary;

(iv) Radon discussed. Measurements have been undertaken (max xxx Bqm-3) and remediation measures successfully implemented. Max level currently xxx Bqm-3;

(v) Radon discussed. Measurements have been undertaken (max xxx Bqm-3) but remediation unsuccessful at reducing levels to below 400 Bqm-3. Levels currently xxx Bqm-3;. Discussing with SI radiation.

Further information

19 HSE IND(G) 210L: Radon in the Workplace (to be updated/ replaced).

20 An up-to-date list of laboratories providing radon dosemeters and measurement services can be obtained from the NRPB website:http://www.nrpb.org/services/radon/index.htm#radon%20in%20workplaces

21 General information for inspectors on IRR99 is given in OC 560/42.

22 Advice on radon sampling and measurement, interpretation of results, appropriate remedial measures and enforcement is available from specialist group radiation inspectors.

23 FOD inspectors requiring further information on enforcement policy should contact Health Unit, Belford House Edinburgh and the appropriate specialist group radiation inspector.

Cancellation of instructions

24 OC 560/20(REV) - cancel and destroy .

25 OC 560/20(REV), Supplement 1 - cancel and destroy .


Updated 2022-11-08