As a rec diver, what to do if I breach my computer's NDL???

[Tigerman]

Youre more likely ABLE to, but you should NOT be more likely to do so "accidentally". Using less gas shouldnt be an "excuse" to not pay attention to your dive plan..

 

[NAM001]

I dont know if KNOWING what will happen is even in the equation. I based my comment on the premis of the OP that an ow suddenly found themselves in deco and what to do / was it a problem. Your alarm going off and saying you are in deco, time wise is vastly different than being 18 min past ndl. Perhaps i read the OP wrong.

"Should" is a very rude word, when it comes to deco and assumptions about algorithms.

I once managed to accumulate 18 minutes of deco on a rec computer, ascending from only 16m/52ft after slipping only 2 minutes beyond NDL before ascending. The deco continued to accumulate on ascent... not disappearing as it 'should'. This was due to my repetitive and multi-day diving profiles (algorithm determined a slower tissue compartment became controlling during that ascent).

As it happens, I was fully prepared for that; diving doubles and rule-of-thirds. I suspect many recreational divers, on a single cylinder and a gas plan no more complex than assuming to "surface with 500psi" would have blown that deco and faced a high risk of DCS. That risk of DCS not assumed by the 'number of minutes'... but by what those minutes represented, in conjunction with knowing why they were calculated as such.

Don't assume anything "should" happen - KNOW what will happen. If you don't KNOW... then accept your assumptions can really hurt you.

 

[Lorenzoid]

"Should" is a very rude word, when it comes to deco and assumptions about algorithms.

I once managed to accumulate 18 minutes of deco on a rec computer, ascending from only 16m/52ft after slipping only 2 minutes beyond NDL before ascending. The deco continued to accumulate on ascent... not disappearing as it 'should'. This was due to my repetitive and multi-day diving profiles (algorithm determined a slower tissue compartment became controlling during that ascent).
. . .

My Suunto seems to have behaved like that a couple of times. I do not rely on any expectations about how it will behave if it goes into deco mode and do everything I can to avoid it.

 

[DevonDiver]

I dont know if KNOWING what will happen is even in the equation. I based my comment on the premis of the OP that an ow suddenly found themselves in deco and what to do / was it a problem. Your alarm going off and saying you are in deco, time wise is vastly different than being 18 min past ndl. Perhaps i read the OP wrong.

I think you misread my post wrong.

I was at 16m/52ft (that was the max depth for the dive), went into deco. I took ~2 minutes to start the ascent, because I had to coordinate my group of divers (I was DM). Deco grew fast on ascent. By the time I hit my ceiling (6m), the deco had risen to 18 minutes.

My divers didn't even hit deco. They hadn't been diving as deep, or as frequently, as I had over the previous weeks. It wasn't that dive... it was the profile of dives over many days. A similar profile to that which many divers might expose themselves to on an intense diving vacation, for instance. Something many do, without knowledge of the implications - either of the deco or how DCS would manifest (badly) if it did occur.

That absolutely fits the premise of the OP.

The lesson communicated is simple - you should assume that deco will clear on ascent. You should understand how/why deco will accumulate - and how that is influenced by your previous diving profiles (multi-day and repetitive). If you don't have that understanding and/or you haven't planned/prepared for an extensive stop, then you should absolutely ensure you don't go into deco.. not ever.

I would hate to think that some of the posts in this thread might promote a false sense of confidence regarding NDL over-stays.

That said, I'm not attempting to scare-monger about deco. Deco isn't scary. Blowing deco IS scary. DCS is scary. Especially so in some 3rd world, undeveloped, diving paradise...

 

[Bob DBF]

Sorry, but WHAT??
Are you actually suggesting that because your SAC is getting better you're probably going to be less observant of your dive plan and that's OK??
If youre violating procedures, atleast fess up to it and admitt that you either did it because youre sloppy or it was intentional. Calling it an "accident" is severly inaccurate. (And yes, I do violate agency standards on a regular basis and I know it and I know I expose myself to more risk than my cert card want me to)

You don't have to be violating procedure, sloppy or intentional. Last summer I made two dives to around 120', the first was fine and I did well over an hour SI and a computer check gave me about 8min or so at depth on the second dive. I made the dive and was within NDL by minutes until the neighborhood of 100' at which point I went into deco. I came out of deco around 50' so it was a nothing deal overall however, it was interesting for a while because it was not expected.

Since then I also watch the runtime of my deep dives, because of my SAC, and plan on being above 60' sooner than I would have before. It also added another reason for me not to do deep stops, which would have added to my deco on this profile. This was all done in 53 degree f water and wetsuit, so I was not looking forward to a deco stop. I extended the safety stop 'till my tank was at 200# and still had the pony as reserve.



Bob
------------------------------------
"the future is uncertain and the end is always near"
Jim Morrison

I think that advocating unsafe and dangerous practices is both stupid and foolish. That is why I don't tell people to do what I do. Dsix36

 

[waterpirate]

From a pragmatic standpoint:
What happened to plan your dive, dive your plan?
What happened to the buddy redundant brain?
What happened to do not push the limits?
What happened to if you violate your puter, make a safe controlled ascent and you are done for the day?

To me these are hard fast rules for recreational scuba. If you find yourself curious about or not able abide by the rules, you should seek more training or stop diving. In this day of multiple agency's teaching accrossed a broad spectrum of approaches to the training, there is no excuse for reckless diving without training. YMMV
Eric

 

[Tigerman]

You don't have to be violating procedure, sloppy or intentional. Last summer I made two dives to around 120', the first was fine and I did well over an hour SI and a computer check gave me about 8min or so at depth on the second dive. I made the dive and was within NDL by minutes until the neighborhood of 100' at which point I went into deco. I came out of deco around 50' so it was a nothing deal overall however, it was interesting for a while because it was not expected.

Since then I also watch the runtime of my deep dives, because of my SAC, and plan on being above 60' sooner than I would have before. It also added another reason for me not to do deep stops, which would have added to my deco on this profile. This was all done in 53 degree f water and wetsuit, so I was not looking forward to a deco stop. I extended the safety stop 'till my tank was at 200# and still had the pony as reserve.



Bob
------------------------------------
"the future is uncertain and the end is always near"
Jim Morrison

I think that advocating unsafe and dangerous practices is both stupid and foolish. That is why I don't tell people to do what I do. Dsix36

Yes, if you went into deco without planning it then it WAS indeed sloppy. If you planned for it, it was no longer accidental.
Your computer does show how much NDL you have left at any given point and there should be no problem adhereing to it, the same way you do your spg unless you have incidents that have to be resolved before you can start your ascent.

---------- Post added January 7th, 2014 at 06:17 PM ----------

If you know the computer is about to go into deco and still continue, its intentional. It doesnt neccesarilly make it stupid, as long as you know what youre doing, but its definetly not accidental.

 

[doctormike]

What happened to if you violate your puter, make a safe controlled ascent and you are done for the day?

Yes, but the OP was specifically asking about what an OW diver should do should they find themselves in this circumstance (their computer going into deco).

So your advice to "make a safe controlled ascent" is potentially dangerous for an OW diver who figures that just means make a safety stop and get on the boat quickly, where the bends can't get them.

Much better for them to remember "figure out what your computer looks like when it goes into deco, figure out what a ceiling means, and then stay below that ceiling until you run low on gas, or until your ceiling clears". Which was the point of this thread...

 

[Tigerman]

Not knowing what the computer is saying unfortunately is a MASSIVE issue, especially with rental gear where the customer often only know where to read depth, time and hopefully NDL (VERY sloppy indeed)

 

[Donnah]

A few weeks ago I took my 15 yr old on a dive with a 135 ft max depth. He stayed up around 120 or so I think. We were using computers (and nitrox) and we went a little into deco. We each had a pony bottle. We had not really planned to put him into deco and for some reason his computer showed more deco than me... maybe 6 minutes. He had an aluminum 80 tank.

I'm totally confused. You were at 135 ft on Nitrox?