An employer must ensure that the exposure of an employee is either prevented or, where this is not reasonably
practicable, adequately controlled: Provided that-
(a) where there is exposure for which there is a restricted limit, the control of the exposure must be regarded as adequate if the level of exposure is below that limit or if the relevant area is zoned and the level of exposure is reduced to below that restricted limit by means of adequate personal protective equipment only after the level has been reduced to as low as is reasonably practicable by any other means than personal protective
equipment; or
(b) where there is exposure for which there is a maximum limit, the control of the exposure must be regarded as adequate if the exposure is at a level as low as is reasonably practicable below that maximum limit: Provided
that in the case of temporary excursions above the control limit, the employer must ensure-
(i) that the excursion is without a significant risk from exposure;
(ii) that the excursion is not indicative of a failure to maintain adequate control;
(iii) that during the excursion, the area is temporarily demarcated and prescribed and identified as
contemplated in regulation 8(b); and
(iv) that the provisions of regulation 11 are complied with.