An employer must review the assessment required by subregulation (1)-
(a) at intervals not exceeding 24 months;
(b) forthwith, if-
(i) the previous assessment is no longer valid;
(ii) there has been a change in a process involving an HBA;
(iii) there has been a change in the methods, plant or machinery, procedures in the use, handling, control or processing of an HBA;
(iv) an incident occurs involving an HBA; or
(vi) medical surveillance reveals an adverse health effect, where an HBA is identified as a contributing factor.