Exceeded NDL by a bit, but computer cleared me. What should I do?

[Orestis82]

I was doing a guided dive to 30m today and was roughly following the guide. I have a habit of checking my computer often, but it’s not 100% there, and I have just started diving deep. Excuses, I know.

My aqualung i300c has a deep stop that triggers automatically, which I didn’t notice this time, but at some point I show the NO DECO and the dive time remaining flashing. I thought it was my DTR alarm triggering and paid no attention (there was no audible alarm). The computer didn’t instruct me to do a Deco stop. I did the usual three minute safety stop at 5m and then surfaced.

When I synced the dive to the Dive Log plan, I see that it has marked a point with red, saying decompression (see image). I am not 100% sure if it is using another algorithm or if it’s picking up NDL data from the computer.

Should I be worried? What should do better next time, apart from monitoring my computer closer next time, and perhaps start Nitrox diving?

 

[ChuckP]

Nitrox on deeper and or longer dives will help but nitrox will not make you monitor your computer. Simply monitor your computer closer, especially when you are getting close to NDL - you'll get a feel for how altering your depth effects your NDL.

You shouldn't be worried, you unknowingly followed your computer, keep it as a positive lesson to follow it more closely.

 

[ToneNQ]

Its been a while since I dived my Suunto, but the deep stop occurred at 30m on my D9, using RGBM. At 15m you're well inside the normal decompression zone and you're offgassing, so its highly likely your deco penalty simply cleared due to ascending. The stop time is based on ascending at 9m/min to the deco stop depth. You've ascended much more slowly. Certainly on the D9 you could just ignore the deepstop if you so desired, the shallower stops are what the computer enforced or it locked you out. If you get yourself onto a deep dive course, quiz your instructor at length. It's all good knowledge.

I did 35m dive for 30mins a few weeks ago, when we turned it was a 2min stop at 12m, but it was a long slow ascent up the slope. By the time we'd ascended to 15m the stop had cleared and we just kept going. I think the total stop required was 3min at 6m, which is awesome. That was a CCR dive so the numbers are not directly comparable, but the theory remains sound.

 

[Orestis82]

Thanks for the replies. I did notice the instructor was staying close to 30m for a longer time and I ascended a bit higher to be safer and preserve air. There was nothing special at the 30m mark anyway.

I did a few sawtooth moves (as you can see in the graph) but I hope it wasn’t too sever.

 

[arew+4]

Thanks for the replies. I did notice the instructor was staying close to 30m for a longer time and I ascended a bit higher to be safer and preserve air. There was nothing special at the 30m mark anyway.

I did a few sawtooth moves (as you can see in the graph) but I hope it wasn’t too sever.

You're fine, get in the habit of checking your gauges at depth related intervals, more frequent when deep less so when shallow, and also increase frequency at end of dive.

I wouldn't call that saw tooth, looks like you're following contour of the reef. I would call it saw tooth when your bouncing up and down in 7-10 meter swings.

 

[The Chairman]

Deep stops are not mandatory and indeed, many argue against them, especially on repetitive dives over several days. The science shows that a few slow compartments are still on-gassing during a deep stop and they become a factor the more deep stops you do in a row. You should be able to turn that "feature" off.

However, I would suggest that your biggest error is in only doing a 3-minute safety stop. Yeah, you were taught that was adequate, but it's really not. Extend it to a full five and ascend stupid slow once it's over. Your body will thank you for it by not having the after-dive drowsies.

 

[Bowers]

Yup, your deco stop was figured at 3 meters and for 2 minutes. So your 5 meter 3 minute safety stop saved you There are other factors to consider when deco diving and i would plan to check your computer regularly and try to avoid getting into deco in the future until you’re trained for all the caveats. But this time around it looks like you have nothing to worry about.

 

[kaylee_ann]

Deep stops are not mandatory and indeed, many argue against them, especially on repetitive dives over several days. The science shows that a few slow compartments are still on-gassing during a deep stop and they become a factor the more deep stops you do in a row. You should be able to turn that "feature" off.

However, I would suggest that your biggest error is in only doing a 3-minute safety stop. Yeah, you were taught that was adequate, but it's really not. Extend it to a full five and ascend stupid slow once it's over. Your body will thank you for it by not having the after-dive drowsies.

Oh, the post dive naps are the best sleep I’ve gotten in years. Slept like a baby. Probably not a good thing lol.

 

[inquis]

Look into the computer manual to confirm how it signals mandatory deco as well as the deep stop. You shouldn't mistake remaining NDL for anything else.

You should also communicate with the DM pre-dive about how to signal them about remaining NDL time when it gets low and do so during the dive.

 

[The Chairman]

Oh, the post dive naps are the best sleep I’ve gotten in years. Slept like a baby. Probably not a good thing lol.

Often that is sub-clinical DCS. Do the full five minutes and longer if possible. If there are people getting on the boat ahead of me, I simply wait at safety stop depth if possible (air and currents permitting) and will time my final ascent to be on the tag line just as the last person clears the ladder. If I'm at a spring after a cave dive, which are usually deco dives for me anyway, circumstances permitting, I add another five to the last stop and then do another five or ten resting on the surface before I start lugging gear out. I would do that on a boat, but them thar boat operators get testy.