312.90. Inspection dive at a site likely to show a pressure differential: Before performing work underwater at a site likely to show a pressure differential, the underwater work area and a width of at least 5 m in the surrounding of the area must be inspected in order to detect any source of suction and eliminate it, if applicable, if it constitutes a danger for the diver.
In addition, the following safety standards must be complied with:
(1) the diver must be lowered underwater so as to progressively go near the area to inspect; and
(2) the diver must be lowered underwater in one of the following manners:
(a) in a cage that complies with section 312.39 and hoisted according to section 312.40; or
(b) attached by a dorsal lifting ring or link to a cable, other than the lifeline, with a breaking strength greater than 20 kN and linked to a locking device.