(1) The prescribed period for giving notice of the occurrence of an event to the chief executive is—
(a) if the event is a death or serious personal injury or the imminent risk of death or serious personal injury, and someone other than the employer was injured or at risk—
(i) as soon after the event as is reasonably practicable; and
(ii) in writing not later than 48 hours after the event; and
(b) for any other event—in writing not later than 7 days after the day the event occurs.
(2) This section is subject to section 83.