1910.426—Mixed-gas diving.
(a) General.
Employers engaged in mixed-gas diving shall comply with the following requirements, unless otherwise specified.
(i)
A bell is used at depths greater than 220 fsw or when the dive involves inwater decompression time of greater than 120 minutes, except when heavy gear is worn or when diving in physically confining spaces; or
(ii)
A closed bell is used at depths greater than 300 fsw, except when diving is conducted in physically confining spaces.
(3)
A diver shall be stationed at the underwater point of entry when diving is conducted in enclosed or physically confining spaces.
(4)
Each diving operation shall have a primary breathing gas supply sufficient to support divers for the duration of the planned dive including decompression.
(i)
An extra breathing gas hose capable of supplying breathing gas to the diver in the water shall be available to the standby diver; and
(7)
An inwater stage shall be provided for divers without access to a bell for dives deeper than 100 fsw or outside the no-decompression limits.
(8)
When a closed bell is used, one dive team member in the bell shall be available and tend the diver in the water.
(9)
Except when heavy gear is worn or where physical space does not permit, a diver-carried reserve breathing gas supply shall be provided for each diver: