4. Certificates of approval given before the coming into operation of this Order by the Chief Inspector of Factories for the purposes of the Lead Processes (Medical Examinations) Regulations 1964, Regulation 32(2) of the Ionising Radiations (Unsealed Radioactive Substances) Regulations 1968 and Regulation 29(2) of the Ionising Radiations (Sealed Sources) Regulations 1969 shall remain in force until revoked under this paragraph by certificate of the Chief Employment Medical Adviser or a Deputy Chief Employment Medical Adviser.