Safety stops are suggested / recommended stops so if its just a label then call it a suggested deep stop. In the day when you did 60 ft/min ascents it was not unusual to do 60 up to 60 ft and stop for a minute or so before continuing to the surface at 30 or less. The consequences involved IMO do not present themselves in the rec world let alone a single dive. If you are dong the 1/2 pressure thing many go from 100 to 30 and then stop to gather themselves prior to being able to settle at 20 for the SS. Happens a lot when there is no line to hold you down. For those that cite continued on gassing, I would say what harmful on gassing is there at 30 ft?
Deep Stops Recreational Divers
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No deep stops for Mrs Flush or myself. We just have a VERY slow ascent rate. The rate of our ascent has a lot more to do with not wanting our dive to end and enjoying as much of the gas still left in our tank than us gaining a larger safety margin. I do not understand folks who rush to the safety stop then on up to the boat? We have seen some really great stuff at the ends of our dives.
I agree with @KenGordon. The implementation of additional stops by dive computer manufacturers may not necessarily follow the half depth or pressure protocol as outlined in the survey. In general, divers tend to follow the ascent profile dictated by their computers rather than follow some rule of thumb.
Ken, I'm curious as to which computer you have that doesn't allow you to turn off the deep stop function?
@rsingler I'm interested in the rational for your statement above. Is it specifically PDIS or a more general statement regarding the deep stop function available on most dive computers offered today?
Eric Sedletzky
Contributor
It sounds to me like several folks are trying to turn simple recreational dives into tech dives.
Deep stops, half depth rule, 30-20-10, stops....on simple recreational dives?...Really??
Where’s the evidence? Or is this just the current fashion statement. Or better yet the current scubaboard fashion statement. Does the rest of the recreational diving world know about all this?
Deep stops, half depth rule, 30-20-10, stops....on simple recreational dives?...Really??
Where’s the evidence? Or is this just the current fashion statement. Or better yet the current scubaboard fashion statement. Does the rest of the recreational diving world know about all this?
Its a reaction to the changes in the dive computer market.
The recreational dive computer manufactures have brought 'technical' dive theory into their range - hence deep stops.
They have also added new computers for the 'technical' diving market.
In addition the specialist technical computer market has grown, OSTC and Shearwater. These companies are now selling computers to the recreational divers - stripped down versions of their trimix computers.
This is part of the reason I am confused by the expression recreational diving.
The PADI definition is No - Stop diving. Which has never really applied in the UK, because we have always taught decompression stops to everyone once they have progressed passed Ocean Diver (the PADI OW equivalent). Nitrox is part of Ocean Diver (our equivelent to PADI OW). The lines have blurred.
I'm looking.
I contacted NAUI headquarters and asked for the research behind their advocacy of deep stops. They pointed to a 2008 study that is a bit controversial. I contacted GUE headquarters more than a month ago to ask for the theoretical basis of Min Deco. I was referred to one of their people who was at the time too busy to respond, but I was promised an answer soon. I have sent a couple of reminder emails, but I have not gotten the response yet. In a ScubaBoard thread, a non-authoritative explanation said that it was a recreational dive application of a Bühlmann decompression program with deep stop GF settings. I am awaiting an official response.
Bob DBF
Contributor
Don't buy the lie, technical diving is recrecreational diving.
Technical Diving was named in the '90's, as I remember, to encompass a particular style of diving, just as cave and wreck were named earlier in diving. Before 1990, the same type of dives were being made by the same recreational divers that are now called technical. It is just a natural progression for a recreational diver who wants to see a lot more of underwater world.
I made a number of what would be called technical dives as a SCUBA diver back in the '70's without any formal certification. Not saying I wasen't trained, but a lot was done with the Navy diving manual and OJT. Except for doing it all on air, the dives were pretty rudimentary for what can be done now, on the other hand tech divers now would never touch the dives without the trimix that is available now. And thinking about it now, neither would I.
There are only a few actual catagories of diving.
Recreational - for fun
Commercial - for $
Military - four Uncle Sam
Scientific - for science
Public Safety - for search and rescue
There might be another, I haven't thought about this in a while so don't remember offhand.
Bob
PfcAJ
Contributor
Deepstops in recreational dives....it sounds like a fashion statement, while most recreational divers have only a little bit of decompression knowledge. Technical divers learned about decompression theory during their courses and are aware of decompression questions that nobody has answered yet.
If you put tissue pressure and ambient pressure in a diagram, this is what a NDL dive looks like:
While descending, ambient pressure increases much faster than the gas pressure in your tissues. While you stay at depth (same ambient pressure), the tissues are ongassing. Once you reach the last point in time, where you swim up to the surface without stopping, and your tissue pressure is below the M-value (green line), your computer displays a NDL time of zero.
And the computer does this for 16 different compartments, each with their own halftimes for off-gassing. The NDL displayed on the screen is the shortest time for each of these calculations.
To off-gas, you need to get above the blue line (Pamb = Ptiss). On a dive shallower than 40m/130ft within the NDL, adding a deepstop will on-gas the mid and slower tissues even more. Doing a safety stop at 5m/15ft for three minutes is way more effective than a deepstop.
If you put tissue pressure and ambient pressure in a diagram, this is what a NDL dive looks like:
While descending, ambient pressure increases much faster than the gas pressure in your tissues. While you stay at depth (same ambient pressure), the tissues are ongassing. Once you reach the last point in time, where you swim up to the surface without stopping, and your tissue pressure is below the M-value (green line), your computer displays a NDL time of zero.
And the computer does this for 16 different compartments, each with their own halftimes for off-gassing. The NDL displayed on the screen is the shortest time for each of these calculations.
To off-gas, you need to get above the blue line (Pamb = Ptiss). On a dive shallower than 40m/130ft within the NDL, adding a deepstop will on-gas the mid and slower tissues even more. Doing a safety stop at 5m/15ft for three minutes is way more effective than a deepstop.
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