Under the Health and Safety at Work (Etc.) Act 1974, the employer bears the principal responsibility to ensure the health and safety of employees and others. Protection from exposure to radon at work is specified in the Ionising Radiations Regulations 1999
These regulations apply to work areas where the level of radon exceeds a defined threshold. One of the fundamental requirements is to reduce exposures to radiation to as low as is reasonably practicable.
Where radon levels are found in excess of 400 Bq m-3 in the workplace, then the first approach should be to apply remedial measures to the building(s) to reduce radon levels to as low as is reasonably achievable.