Question What's your safety stop depth?

[EFX]

Despite what I wrote earlier in this thread that SurfGF makes safety stops superfluous I still do them. I do them for two reasons: (1) my buddies religiously do them and I stay with my buddies and (2) I'm in no hurry to get out and find them fun to do. Occasionally, I do some light deco of less than 5 minutes. All those stops have been at 10 ft. Oddly enough, when I'm done with the deco the computer directs me to do a 15 ft safety stop! The manual doesn't say why unless I missed it somewhere. I'm wondering if it's because I've got the computer set for rec mode. Shearwater, care to comment?

 

[tursiops]

Despite what I wrote earlier in this thread that SurfGF makes safety stops superfluous I still do them. I do them for two reasons: (1) my buddies religiously do them and I stay with my buddies and (2) I'm in no hurry to get out and find them fun to do. Occasionally, I do some light deco of less than 5 minutes. All those stops have been at 10 ft. Oddly enough, when I'm done with the deco the computer directs me to do a 15 ft safety stop! The manual doesn't say why unless I missed it somewhere. I'm wondering if it's because I've got the computer set for rec mode. Shearwater, care to comment?

The Nitrox Recreational Mode manual for the Petrel says:

6.1. Safety Stop A safety stop is an optional stop added to all dives before surfacing. Safety stops can be set to fixed times of 3, 4, or 5 minutes, set to adapt based on dive conditions, or turned off completely. See System SetupDeco Setup for options.​

And then it says in 6.2:

Decompression stops will appear in place of the safety stop when required. After the decompression stops are completed, the safety stop will begin.​

It also says you can ignore it with no penalties.
So I guess you leave it running if you don't care, and shut it off if you do care.

 

[EFX]

The Nitrox Recreational Mode manual for the Petrel says:

6.1. Safety Stop A safety stop is an optional stop added to all dives before surfacing. Safety stops can be set to fixed times of 3, 4, or 5 minutes, set to adapt based on dive conditions, or turned off completely. See System SetupDeco Setup for options.​

And then it says in 6.2:

Decompression stops will appear in place of the safety stop when required. After the decompression stops are completed, the safety stop will begin.​

It also says you can ignore it with no penalties.
So I guess you leave it running if you don't care, and shut it off if you do care.

Thanks. I should have read the manual more carefully. Shearwater, no need to respond.

 

[dmaziuk]

Thanks. I should have read the manual more carefully. Shearwater, no need to respond.

My cressi does the same thing, except for directing me to the deeper safety stop. It's probably not unreasonable when you think about it, but it sure does look silly.

 

[Dan]

No you don't. I typically run my Perdix in rec mode because the safety stop timer is automatic once the safety stop depth is reached. In tec mode, which I do use occasionally when running VPM-B +2, the timer must be started, stopped, and reset manually which for me is a PITA. Here is a screen shot of the main screen on my Perdix. I'm running the latest version of the software (84). SfGF is the surface GF, GF99 is the GF at the current depth, COMP is compass:

View attachment 702991

109 days of surface interval? It's time to get back into the water!

 

[clownfishsydney]

When I go well into deco, I normally have the last stop at 3m. Do you go back to 5m for additional safety stop or do you extend your deco stop further? Not long ago someone I dived with went into deco, despite same profile, his dive computer was way more conservative, so, while I was doing my optional safety stop at 5 he went to 3 to clear his computer and joined back to me. I thought that was unusual, I would have either stayed at 5 until my computer showsno deco obligation + safety stop or straight to 3m and clear and surface.

I stay at my last depth which is 4 m normally.

 

[scubaozy]

How does surfgf work? Does it track against the fastest compartments or aggregates all of them?

 

[Raphus]

How does surfgf work? Does it track against the fastest compartments or aggregates all of them?

All of them.
It displays the gf of the most saturated tissue, if you would teleport to the surface at that moment.

 

[EFX]

All of them.
It displays the gf of the most saturated tissue, if you would teleport to the surface at that moment.

In my spreadsheet I calculate CurGF (what Shearwater calls GF99) and SurGF based on the controlling tissue compartment (CTC). You would think that the most saturated TC would be the leading TC but this isn't always the case. Fast TC's have shorter half-times so they saturate quicker than other TC's but they also off-gas more quickly. While they might be the CTC early in the dive, as the ascent progresses they off-gas to the point where they no longer control the dive.

In order to keep divers safe from DCS (decompression sickness, AKA "the bends") the amount of gas flowing out of the tissues into the blood to be released by the lungs must be kept below safe levels. Sometimes, the gas pressures inside the tissues become so high that the flow out of these tissues exceeds safe levels on ascent. To manage these levels it becomes necessary to make stops at various depths upon the ascent to allow the tissues to off-gas at a safe rate. Algorithms determine these stops by calculating a ceiling for which the diver must stop at before proceeding to a shallower depth.

The CTC will have the deepest ceiling. This is true for both deco and NDL dives. For NDL dives the ceiling is used to calculate the time remaing at depth which is the NDL time. What I do in the spreadsheet is calculate the ceiling for all TC's throughout the dive. The TC with the deepest ceiling becomes the CTC and it's gas pressures are used in the calculation for both CurGF and SurGF. If you are interested in the calculation see my post at:

What's your SurfGF and how does it compare to your (Rec) GFHi?

But what system should I have used to do twenty-five 80-100' dives in a row, 4-5 a day (counting night dives), as I drank in the sights of the second dropoff on Bonaire last September? It wasn't DSAT, and it wasn't 95/95. I did 27 dives in TCI in 5.5 days in August. Just like you said. Every...

scubaboard.com

 

[scubaozy]

All of them.
It displays the gf of the most saturated tissue, if you would teleport to the surface at that moment.

I am now envious, I paid good money for my garmin and I found out here it cannot even teleport ;-).
Btw, how is this different from old fashioned computers which show tissue load bar on the side? Only difference being it is interpolated to surface pressure and converted into percentage. How do you folks know you will not be bent by non controlling compartments? This whole thing sounds to me like bs production at the first look but when now when I looked around, there quite a few discussions on this. Am I going to be happier ignoring this or am I missing something out that will change my life?