No deco time proximity.

[scubadada]

From an NDL time of 0, you are able to make a normal, direct ascent to the surface, with a low probability of DCS, as dictated by the decompression algorithm you are running. Of course, most divers do a routine, 3 minute safety stop, further decreasing the risk of DCS. As I have grown older, I tend to increase my safety stop to 5 minutes if I have come within several minutes (3-5) of decompression. The decision of how to deal with these situations is personal.

 

[Coztick]

All computers offer an accurate gauge of your NDL time.
While the numbers may vary a little based on algorithms or conservatism, they are a real time consistent guide.
The question is whether it is accurate for you.
Considering the seriousness of exceeding your NDL limits, pushing closer to the computers NDL limits should be done gradually and with conditions in mind.
It took 80 dives before I pushed my Gekko 5 min into deco on Punta Sur below 100 fsw but by then I knew ascending to half that depth would clear the obligation.
I've since dropped suunto for a vt 4.1 so I will be playing, cautiously, with D sat and Pz+ to see how our limits compare.
I haven't had any signs of dcs but I know those limits are there and there are also many variables.
If you think you've pushed your personal limits, extend your safety stop proportionally and surface very slowly.
Listen to your body.
So my answer would be only you can find when you have to ascend by methodically easing closer.
I think the most sensitive person would get bent pushing the limits of the most conservative computer while the hardiest of diver has no issues pushing limits of the most liberal computer.
Its A computer, not YOUR computer.

May the experts correct me,
Cheers, Kevin

 

[NAM001]

I am having a long time discussion with a buddy about the no deco time shown in a computer. How close can you get to the zero time while diving, without risking too much. Some opinions are to go up when you reach the 10 min mark, some consider the 5 minute mark.

look at it this way NDL is like a speed limit on a curve for all vehicles , semi's cars and trucks motorcycles. It is a swag value. (sientific wild ass guess) but a tested one. much like a speed limit you have to decide is the limit for all year or do you reduce speed even more in snowy weather. I certainly would never entertain a suit toteh computer company because i got bent for staying 1 minute over the limit. Imo you can stay past it perhaps under certain conditions. I select not push my luck. i ensure i am on my way up prior to the ZERO time left. I also do the dives deep portion first and then hang out shallower if possible. I get looking for the buddy about 5 min left and coordinate the upcoming ascent to safety stop. If i have been working i may do it earlier. my buddy does the same. first to say head up and we both go. Any slight over stay can probably be remedied with a long surface interval. the real question perhaps is why does with all things equal one computer say ndl is 18 minutes and another computer says 21 minutes. My reccomendation would be to set you computer for conservative and go up when the clock says 0. if you set it for liberal it may say 3-5 minutes left. This is why you have to know your computer. it is a tool and it does just what yo tell it to do . even to lie.

 

[Blasto]

I am having a long time discussion with a buddy about the no deco time shown in a computer. How close can you get to the zero time while diving, without risking too much. Some opinions are to go up when you reach the 10 min mark, some consider the 5 minute mark.

To zero.
But the closer you get to zero:
* The longer you should ascend. There is no definitive guideline, but an easy rule would be to make your safety stop mandatory if you get to 5 min NDL, and add a stop minute for every next minute. So at zero your 3-minute safety stop becomes a mandatory 8-minute one.
* The more air you need yo have when you begin your ascent. This is both to accommodate the longer stop and to provide compensatory safety margin. Probably begin mandatory ascent at 1/3 tank pressure as you remove the NDL margin.
NB: "Ascent" in this context means dive over, going to the safety stop, not just to a shallower level of a multi-level dive site.
* The more important air supply redundancy is. If you're getting very close to NDL, you need to have a RAS (just a small pony) or at least be very close to a reliable long-term buddy for the last minutes of the dive.
* The better you should be at handling emergency deco. At a very minimum, absolutely learn what ceiling means, where it is shown on your computer, and practice simulated deco if possible.

The reason for these precautions is that things happen, and if you routinely get down to 0 NDL, you will sometimes go below, into deco. You should absolutely know what to do if you do. There's a lot of stories about recreational divers that send their computer into deco mode and then screw themselves up, not knowing what their computer is telling them.

Another reason not to go too close to NDL is subclinical DCS - minor damage that manifests as post-dive fatigue. You'll feel much more tired after repeatedly diving down to zero NDL than after multiple conservative dives 10 minutes short of your NDL.

This can be mitigated by treating near-NDL ascent as deco at low GF, and some computers can be set that way. I'm assuming strictly recreational (no-deco) diving for everything above. Planned deco itself can be quite safe and easier on your health than riding NDL up to zero - if you have all four of gear redundancy, pre-dive gas planning, technical deco training, and a well-communicating team (and very unsafe if just one of these elements is missing).

 

[dmaziuk]

Some opinions are to go up when you reach the 10 min mark, some consider the 5 minute mark.

PADI RDP says the former bunch may never dive to 130' or deeper (grey cells aside).

 

[hxtk]

In my opinion, conservatism should be added with the algorithm. If I think I can't safely ascend with seconds left on the NDL clock at my current depth then I'll make the NDL clock run faster by adjusting the conservatism until I am comfortable with it.

Therefore, the only buffer I apply to my NDL clock is problem solving time, equal to the problem solving time I used when planning minimum gas. Usually this is 1-3 minutes, but it could be more depending on my familiarity with the site and the potential for hazards.

 

[happy-diver]

Well once again, talking for talkings sake, there are those that compute, those that dive and those
that do not compute, and considering that I can't remember the last time POTUS asked me to pushit
to the max with regards to NDLs and help him save the world, I spend my dives within limits working this

 

[NAUI Wowie]

I am having a long time discussion with a buddy about the no deco time shown in a computer. How close can you get to the zero time while diving, without risking too much. Some opinions are to go up when you reach the 10 min mark, some consider the 5 minute mark.

25% of people have holes in their heart. I guess they call it a PFO? Hope I got that right. So basically if you are the 1 in 4 normally nothing happens. OR you can die if you are even within safe guidelines.

how to test for hole in heart? hey its 1 in 4 .... they wont test for it if you have no symptoms.

and even with a pfo you still can go your whole life with no outward signs diving all your life.

every time you push a boundary you may find you have DCS. or even not getting near a limit you will still get DCS. If you go scuba diving you risk dying just like hang gliding and motor cycle riding.

There are world famous scuba divers that have pushed limits and not made it. and some get lucky.

insert clint eastwood quote here

 

[Tippytoes12]

It’s very important to be aware of your own personal baseleine risk of DCS. The risk factors are set out clearly in the OW manual and we should all be very conscious of them.

My recollection is that the tables and hence the computer algorithms were developed with data from US military personel , so fittish , youngish men. Divers are less young and less fit and have other risk factors may want to aim to be more conservative than their computer advises.

Just my humble opinion !

 

[jadairiii]

2 weeks ago my buddies and I did a long scooter dive (trimix), started in 125' and end up in 20'. We all were using the same computers, they had 15min of mandatory deco, I had none........obviously my computer was set a tad more aggressively....

So the answer to your question; depends on who you ask.