19.—(1) A user who undertakes a contained use involving micro-organisms shall apply the containment measures set out in the applicable table in Part 2 of Schedule 8, where and to the extent required in the column of the appropriate containment level.
(2) A user need not apply a containment measure required for the appropriate containment level where—
(a)the risk assessment, or any review of the risk assessment, shows that the containment measure is not necessary or practicable for a specific activity;
(b)the notifier of the contained use has provided justification in writing to the competent authority; and
(c)the notifier has received the written agreement of the competent authority that the containment measure need not be applied.
(3) A person responsible for the contained use shall review the containment measures applied—
(a)at suitably regular intervals; and
(b)immediately, if that person suspects that—
(i)the containment measures are no longer adequate;
(ii)the class assigned to the contained use in the risk assessment is no longer appropriate; or
(iii)in the light of new scientific or technical knowledge, the risk assessment is no longer valid.