Section 4.
AUXILIARY BREATHING SYSTEMS
1.
BUILT-IN-BREATHING APPARATUS. Built-in-breathing (BIB) apparatus should
be provided in the chamber for use in rapid descent mixed gas dives,
emergency treatments, oxygen therapy, and decompression treatment. Mask,
oral-nasal, or mouthpiece type apparatus can also be used to protect against
inhalation of products of combustion, excessively hot gasses, or against
toxic gasses in the event of chamber atmosphere contamination.
The number of BIB's provided should be greater than the maximum number of
chamber inhabitants to allow for the possibility of some of the masks being
damaged or being made inaccessible during an emergency. Complete sets of
BIB's should allow access to all internal chamber controls.
A typical BIB system is shown in Figure 6-25. The high pressure oxygen or
mixed gas is plumbed to the mask supply regulator then through a hull stop
valve to the diver BIB mask. The supply regulator is a dome-loaded tracking
regulator which is loaded using the chamber internal pressure and regulates
the supply pressure to 100 psig over chamber pressure. The regulator on the
BIB mask reduces the pressure to a normal demand pressure. A hand-loaded
regulator is less expensive and works effectively if the chamber occupants
are always near the regulator to make adjustments during the mission. In
either case, the regulator must automatically exhaust ascent modes. The
overboard dump regulator must be a negative bias regulator with a maximum
discharge pressure of 15 psig. Keyed disconnects will prevent wrong hose
connections.
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