Deep stop question

[TSandM]

The Deco Stop

The Deco Stop

The Deco Stop

These are some with some interesting conversation.

 

[Age]

Quick question:
If I'm diving EAN32 and I want to follow NAUI's procedure for deep stops (rule of halves) then I stop for one minute at half my maximum depth but 3 metres (10 feet) deeper to take the EAD into consideration. Have I got that right? If so, then why doesn't the NAUI nitrox course book address this.

 

[Charlie99]

Quick question:
If I'm diving EAN32 and I want to follow NAUI's procedure for deep stops (rule of halves) then I stop for one minute at half my maximum depth but 3 metres (10 feet) deeper to take the EAD into consideration. Have I got that right? If so, then why doesn't the NAUI nitrox course book address this.

I don't know if NAUI has answered this question.

My recommendation is to just do the half-depth stop at half-depth. Your N2 loading is lower on EAN32 than on air, so you should be able to ascend further (get shallower) on EAN32 before you have the same amount of bubble formation as on air. Only ascending to the same half depth gives you a bit of extra safety margin.

When at the half-depth point, on EAN32 you will be ongassing less into the slow and medium compartments, while at the same time offgassing more from the faster compartments than you would on air.

Applying the EAD calculation would be forcing your initial deep stop unecessarily deep.

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While not part of the NAUI rules, I adjust my deep stops when doing multilevel profiles. I base my deep stop on where I have been for the last 10 or 15 minutes rather than max depth of a brief excursion earlier in the dive. For example, if I spend 5 minutes at 130', then 5 at 100', then 10 minutes at 80' to 70', I will do my deep stops somehwere around 45' rather than at 130/2= 65'.

Charlie Allen

 

[Age]

I don't know if NAUI has answered this question.

My recommendation is to just do the half-depth stop at half-depth. Your N2 loading is lower on EAN32 than on air, so you should be able to ascend further (get shallower) on EAN32 before you have the same amount of bubble formation as on air. Only ascending to the same half depth gives you a bit of extra safety margin.

When at the half-depth point, on EAN32 you will be ongassing less into the slow and medium compartments, while at the same time offgassing more from the faster compartments than you would on air.

Applying the EAD calculation would be forcing your initial deep stop unecessarily deep.

-------------

While not part of the NAUI rules, I adjust my deep stops when doing multilevel profiles. I base my deep stop on where I have been for the last 10 or 15 minutes rather than max depth of a brief excursion earlier in the dive. For example, if I spend 5 minutes at 130', then 5 at 100', then 10 minutes at 80' to 70', I will do my deep stops somehwere around 45' rather than at 130/2= 65'.

Charlie Allen

Thank you for this,

While I'm still trying to wrap my brain around all of this, I should say that the latest NAUI Nirtox manual would agree with you i.e. "Rule of halves" (even with nitrox), but having said that, I like your pragmatic approach. Something tells me that this hasn't been figured out yet as Deep Stops are still controversial and relatively new. I know that my Suunto Mosquito gave me a deeper conventional safety stop when I dove Nitrox, much to my surprise.

 

[limeyx]

Thank you for this,

While I'm still trying to wrap my brain around all of this, I should say that the latest NAUI Nirtox manual would agree with you i.e. "Rule of halves" (even with nitrox), but having said that, I like your pragmatic approach. Something tells me that this hasn't been figured out yet as Deep Stops are still controversial and relatively new. I know that my Suunto Mosquito gave me a deeper conventional safety stop when I dove Nitrox, much to my surprise.

Honestly, as Charlie said, it probably doesn't make any difference really given the range of depths you are talking about.

For recreational diving, your first stop might be 60,50 or 40 feet for a deep dive, and honestly either of them will probably work just fine, although I would tend to round shallower than deeper as you breathe less gas shallower, and you want to make sure you are not on-gassing too much.

Even for deeper dives (150-200) a "rough approximation" is plenty fine, and there I round shallower too.

 

[UWSojourner]

If you dive withing the NDL of your dive watch:

IF YOU CAN, stop 1/2 of max depth for 1 minute. Then stop 1/2 of 1st stop depth for another minute then 2-5 minutes at 10-20ft as you see fit.

If you are within then NDL then remember that you still have a direct ascent to the surface. Do it as slow as you can, but ascend as NEEDED. They don't call it the NO DECOMPRESION LIMIT for nothing. Yes, its better to do a slow ascent (even stops as described above). But if you are a beginner, then do your ascent as needed and as slowly as possible.

Cheers and safe diving.