Any area - designated as such by an employer
and under his control - which has been identified by an assessment made by him as an area in which:
(a) it is necessary for any person who enters or works in the area to follow special procedures designed to restrict significant exposure
to ionising radiation
in that area or prevent or limit the probability and magnitude of radiation accidents or their effects; or
(b) any person working in the area is likely to receive an effective dose greater than 6mSv a year or an equivalent dose greater than three-tenths of any relevant dose limit referred to in Schedule 4 in respect of an employee aged 18 years or above.
The employer shall ensure that any such designated area is adequately described in local rules and that (i) the area is physically demarcated or, where this is not reasonably practicable, delineated by some other suitable means; and (ii) suitable and sufficient signs
are displayed in suitable positions indicating that the area is a controlled area, the nature of the radiation sources in that area and the risks
arising from such sources.