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Chapter 5 — 11
With most equipment, it is necessary for the diver to create a slight negative pressure in the
mouthpiece during each inhalation in order to activate the demand valve mechanism. This negative
pressure should be minimal or breathing becomes tiring. A regulator which is easy to breathe from at
the surface, may not necessarily be able to deliver the large gas flows required during exertion at
depth. When choosing a regulator, divers should refer to independent (e.g. U.S.Navy) testing.
Console, incorporating compass,
pressure (contents) gauge,
decompression computer (timer, depth
recorder, ascent rate monitor,
Low pressure hose
Secondary
(octopus)
demand valve
First stage regulator
!
Inflation hose
Buoyancy
compensator,
inflation button
Primary regulator
(2
nd
stage regulator)
or demand valve
Oral
inflator
Fig. 5.13
A scuba rig