Appropriate designation of classified persons

This information will be of interest not only to those employers who routinely work with ionising radiation, but also to those employers (including the self-employed) whose employees occasionally work where sources of ionising radiation are present eg contractors working temporarily on licensed nuclear sites.

When is classification appropriate?

Radiation employers (ie employers who in the course of a trade, business or other undertaking carry out work with ionising radiation) are required, under IRR99, to designate as classified persons those employees who are likely to receive an effective dose in excess of 6mSv per year or an equivalent dose in excess of 3/10ths of any relevant dose limit (regulation 20). Where this is the case, relevant employees will be made subject to medical surveillance and have their doses appropriately assessed and recorded.

The employee's own employer is responsible for determining whether classification is appropriate, however it should be noted that duties imposed on the employer are also imposed on the holder of a nuclear site licence in so far as those duties relate to the licensed site and in such cases it is important that there is co-operation between employers as required by IRR99 Regulation 15. In determining the need for classification the employer is likely to need to consider a number of factors and may also consult other parties, including a radiation protection adviser (RPA), to obtain sufficient information to decide whether classification is necessary.

The overarching duty in IRR99 is to restrict exposure so far as is reasonably practicable (IRR99 regulation 8(1) and L121 paragraphs 59-118). Designation of individuals as classified persons should be considered when, despite all reasonable steps having been taken, there remains a likelihood that the dose criteria specified in Regulation 20 will be reached. The flow chart may help in deciding whether classification is appropriate.

Employees may be required to enter controlled areas as part of their work. Where this is the case, such entry is only permitted to those designated as classified persons or those working in accordance with suitable written arrangements. Written arrangements must ensure that working practices are planned to ensure that radiation doses to individuals are below those levels that would require them to be designated as classified persons. In accordance with Regulation 18(3) personal dose monitoring or monitoring by other suitable means is required to demonstrate appropriate restriction of exposure.

Classification should not be used to avoid the work involved in preparing suitable written arrangements.


The decision as to who needs to be designated as a classified person should be relatively straightforward where work with ionising radiation is undertaken by employees with a single employer and where exposure of any other employer's employees is unlikely.

The radiation employer should, in consultation with their RPA, carry out an assessment of the risk associated with the proposed work in accordance with regulation 7 of IRR99 or regulation 3 of the Management of Health and Safety at Work Regulations 1999 (MHSWR). The output of the risk assessment should be the key to the decision-making process and the need to designate certain employees as classified persons is likely to be one outcome (L121 paragraphs 36 to 58 cover prior risk assessment).

If an assessment of the potential exposure shows that the work could be done by employees who are not classified persons, HSE would normally expect entry into controlled areas to be allowed under suitable written arrangements.

However, if the assessment of potential exposure shows that restriction of their doses below the levels specified in regulation 18(2) IRR99 could not reasonably be ensured even with written arrangements, people working in the area should be classified. Entry under suitable written arrangements should not involve a system of work sharing simply to avoid classifying the people working in the controlled area.

Cooperation between employers

The cooperation needed when employers share the same workplace is discussed in paragraphs 241 to 242 of L121. Paragraph 243 of L121 discusses the cooperation needed if an employee has more than one employer. See 'Examples' for further guidance on these situations.

Exposure caused by other employers' work

If it is likely that an employee will be exposed to ionising radiation in another employer's work area, or as a consequence of another employer's work, then the two employers must exchange enough information to allow each to comply with their statutory duties (Regulation 15 of IRR99 refers, as does regulation 12 of MHSWR). Information regarding both potential and likely exposure to ionising radiation should be shared, along with details of any controlled areas that have been designated on sites to which access is required. This helps employers to judge whether they should classify their workers.


  • An engineer for a firm that maintains office equipment needs to visit a site to fix a photocopier. Enclosure radiography is carried out on these premises. Following consultation between employers, it is clear that the engineer has no need to either work in or pass through any areas where he could receive exposure to ionising radiation. As entry to a controlled area is not required, neither designation as a classified person nor written arrangements are necessary.
  • A contact welder is to be used to weld modified pipe work in close proximity to the reactor of a nuclear submarine. A risk assessment has been performed and there is potential for significant exposure to ionising radiation from several likely exposure routes. The welder is likely to perform similar work in controlled areas at a number of sites in the course of the year. On this basis the employer has decided to designate the welder as a classified person.
  • A service engineer for a firm that maintains laboratory equipment needs to visit a site to carry out service work. Although the equipment itself does not contain any sources of ionising radiation, it is located in a controlled area. The site employer calculates that the service engineer could receive an associated dose of 2µSv per visit. Although designation is unlikely to be appropriate, suitable written arrangements under IRR99 will be necessary to allow entry to the controlled area.
  • A licensed nuclear site has a problem of vermin control across the whole site and wishes to use a specialist pest control firm. The firm consults the licensee and establishes that, in the course of this work, the technician would need access to many areas across the site. The firm uses the services of the licensee's RPA and, although the technician would need to pass through numerous controlled areas, it is evaluated that the potential and actual dose would be far below that where designation would be required. The firm concurs with the evaluation and written arrangements under IRR99 (that include assessments of dose) are implemented to allow the technician to enter all required areas.
  • A radiopharmacist routinely receives doses to the hands of the order of 20 mSv in every 8 week period of dose assessment. As she is approaching 3/10ths of the appropriate dose limit of 500 mSv per year, designation as a classified person will be necessary.
  • An NHS Trust concluded, as part of their risk assessment for interventional radiology, that all consultant radiologists doing this work were to have whole body, hand and leg doses assessed for a trial period of three months. Results indicated that classification was not necessary, although these employees would still be subject to routine personal dosimetry for their work in controlled areas. The Trust revisited the risk assessment when two of the three radiologists resigned. As the third would now cover a significantly increased interventional workload, and based on projected doses to the hands particularly, the Trust decided that this remaining individual should be classified. The continuing need for classification was then subject to periodic review.

Employees having multiple employers

Where an employee has several employers, cooperation will be necessary to ensure that relevant information, typically relating to exposure, is shared. For example, where an interventional radiologist works for both an NHS Trust and a private hospital, both employers have a duty to share information in relation to the total dose the employee is likely to receive, to determine whether classification is appropriate. This cooperation should begin in advance of work, because classification relates to projected doses before exposure is incurred.

Checklist for classification

Should the employer decide that designation as a classified person is appropriate, the actions outlined in the checklist should be taken. A periodic review of the continuing need for classification should be undertaken.

  • Is the employee 18yrs or over?
  • Has Appointed Doctor (or Employment Medical Adviser) certified employee fit for proposed work?
  • Has employee been informed that they are a classified person?
  • Have suitable arrangements for dose assessment and record keeping been made with Approved Dosimetry Service?
  • Is a radiation passbook required and if so, has it been provided?
  • Has appropriate training been given?

Classification flow chart

Classification flow chart

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Updated 2023-09-27