13.—(1) Subject to paragraph (2), the Executive may by a certificate in writing exempt—
(a)any person or class of persons;
(b)any substance or preparation; or
(c)any class of such substances or preparations,
from all or any of the requirements of, or prohibitions imposed by, these Regulations.
(2) An exemption granted under paragraph (1) may be granted subject to conditions and to a limit of time and may be revoked by the Executive at any time by a certificate in writing.
(3) The Executive shall not grant an exemption pursuant to paragraph (1) unless, having regard to the circumstances of the case, and in particular to—
(a)any conditions 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 neither the health nor the safety of persons who are likely to be affected by the exemption will be prejudiced in consequence of it.