17.—(1) Subject to paragraph (2) and to any of the provisions imposed by the Communities in respect of the free movement of dangerous substances, the Executive may, by a certificate in writing, exempt any person or class of persons, substance or preparation dangerous for supply or carriage, or class of such substances or preparations, article or class of articles, from all or any of the requirements or prohibitions imposed by or under these Regulations and any such exemption may be granted subject to conditions and to a limit of time and may be revoked at any time by a certificate in writing.
(2) The Executive shall not grant any such exemption unless, having regard to the circumstances of the case, and in particular to—
(a)the conditions, if any, which it proposes to attach to the exemption and
(b)any requirements imposed by or under any enactments which apply to the case,
it is satisfied that the health or safety of persons who are likely to be affected by the exemption will not be prejudiced in consequence of it.