Just some comments -- stops in general. All this
comes from considering gas seeds in the body that
may get excited into growth by any kind of compression-decompression from some semi state
of equilibration at one given ambient pressure.
The why, when, and how are too long for this posting -- but see TDID for instance.
According to "half correct" deco theory (Haldane dissolved gas) shallow stops remove dissolved gases and are standard. According to modern deco
theory, deep stops are better as preparation to enter the shallow zone -- hence tables like RGBM etc. for deep and extended range diving. Deep stops help to restrict bubble formation and growth, while shallow stops ala Haldane staging
treat bubbles at reduced pressure. The biggest
differences here come into play with deep and deco
diving, not recreational diving. WKPP, NAUI Tec
Ops, and LANL Countermeasures have been diving the new (dual phase) RGBM way to stage divers for many years now. NAUI has just released a set of RGBM
tables for recreational diving (no groups, no calcs, no fuss), and the mixed gas, deep stop, deco versions for tec, military, scientific,
commercial diving is coming -- tested and validated on the extreme envelope. Recreationally, RGBM comes into play for repets,
reverse profile, multiday, FAD in a natural way
that can be locked onto earlier tables, meter algorithms, software, etc. But on the tec side,
all is new ground and the old Haldane stuff goes out the window -- where it should have gone even a
century ago.
Safety stops for dives in the shallow zone
(down to 30 fsw) are not really necessary -- but
a good idea to slow ascents. From depth, deep
stops and shallow safety stops work together. Deco divers generally switch to high oxygen mixes in the shallow zone, add some time to required stops
in the same zone, and come up at 1 - 2 fsw/min
from their last deco/safety stop. With deep
stops first, the time in the shallow zone is cut
down, with overall deco time LESS than that
required by Haldane lore.
For recreatational diving, you can make safety stops in the 15 fsw (shallow) zone until you run
out of air with virtually NO impact upon your
next (repet) dive, when next dive has a SI greater
that 45 - 70 minutes. Or get bored. Or turn
blue in the face.
Bruce Wienke
Counterterror Dive Team Ldr.
PS -- All this is also in Technical Diving In
Depth and yes, I wrote it. Also,
magazines like Advanced Diver and Immersed
feature nice articles on same.