Decompression Stop Guidelines - What we have to do if got deco alert?

[Centrals]

According to whom?

I don't believe I have ever been in a situation where I had two hours between NDL dives while using a commercial operation.

I was taught to plan 3hrs surface interval between two decompression dive. The rule has not been altered since 1998. Never ever had any issue so I am not going to change the practice.

As for non decompression dive then 1 hr is usually enough between dive unless one is doing several relative deep dives.

Answer to the OP question: Just follow your computer instruction. Subsequent dive would be interesting because it all depends on the algorithms used in the unit.

 

[Gareth J]

According to whom?

I don't believe I have ever been in a situation where I had two hours between NDL dives while using a commercial operation.

I just checked through this years charters. The shortest surface interval was 2:33 minutes.
That was an Ocean diver (Eqiv’ PADI OW) trip and we wanted to get away early for the return home.
The Scapa trip, all the surface intervals were over 3hours

 

[boulderjohn]

I don't believe I have ever been in a situation where I had two hours between NDL dives while using a commercial operation.

I was taught to plan 3hrs surface interval between two decompression dive.

I was clearly talking about NDL dives.

 

[boulderjohn]

I just checked through this years charters. The shortest surface interval was 2:33 minutes.
That was an Ocean diver (Eqiv’ PADI OW) trip and we wanted to get away early for the return home.
The Scapa trip, all the surface intervals were over 3hours

Since I wasn't there, I won;t challenge it, but I have certainly never seen that.

Can you cite any authoritative source calling for a minimum of 2 hours between NDL dives? If you use tables, it is possible to plan a dive with no SI at all.

 

[Gareth J]

Since I wasn't there, I won;t challenge it, but I have certainly never seen that.

Can you cite any authoritative source calling for a minimum of 2 hours between NDL dives? If you use tables, it is possible to plan a dive with no SI at all.

The longer the surface interval, the more you off gas, the more NDL time you have for the second dive.
Some dive computers don’t like back to back dives with short surface intervals. The Uwatec and Suunto’s from memory.

I can’t imagine a UK dive charter cutting the surface interval down to under 2hours.

Scapa they really don’t like surface intervals under 3hrs. They structure the day to ensure you get a minimum of 3hours.
Like visiting Lyness museum, the Italian chapel etc
In Scapa it reduces helicopter rides!

 

[tursiops]

All dives are deco dives.

I'm really tired of hearing this. It is a gross simplification, and technically incorrect unless you also specify what you mean by "deco." If by deco you mean absorbed some N2, then OK. But at the 99.9% level, what we mean by "deco" is so much N2 absorbed that it cannot be otherwise safely released. Otherwise, we could not dive at all.

 

[L13]

I'm really tired of hearing this. It is a gross simplification, and technically incorrect unless you also specify what you mean by "deco." If by deco you mean absorbed some N2, then OK. But at the 99.9% level, what we mean by "deco" is so much N2 absorbed that it cannot be safely released. Otherwise, we could not dive at all.

What I mean is that on all (non-trivial) dives, absorbed N2 will be released during your ascent. This physiological phenomenon during the ascent is called decompression. The ascent needs to be such that excess N2 is less than your chosen limit.

For dives approaching NDL, you would exceed the limit if you teleported to the surface, but in reality you deco sufficiently during the ascent to be below the limit.

If you exceed NDL, you need to further slow the latter part of the ascent to prevent exceeding your limit while in the water, traditionally done with discrete successively shallower and longer stops. We traditionally call these dives deco dives, but in reality all (non-trivial) dives have nitrogen decompression occuring on the ascent.

A safety stop is a deco stop, it just isn't necessary to reduce N2 below the limit before surfacing.

 

[Belzelbub]

Thank you for all your valuable comments.
Just to clarify, her dive computer was not locked. It seems that they clear the deco stop but the Suunto start again with 3min safety stop afterwards, but they decide to surface. The manager was trying at the dive shop to find the value of the no flight time, to decide if they ban her for diving 48h (not sure why this NFT value specifically), as he couldn’t manage to display it in the Suunto, she was cleared for the next day.

Could someone explain what indication the no flight time would have given? I don’t think I have this value on my Shearwater Peregrine.

Not sure on the Suunto. I've never noticed a No-Fly indicator on my Shearwater, either. On my Garmin, I get an aircraft icon, and there is a red ring around the display corresponding to 24 hour increments. The ring ticks down as my time out of water increases.

That said, the dive shop looking for the no-fly time to determine ability to dive again is strange. On some computers, like my Garmin, the no-fly time can be either a fixed 24 hours or standard. I have mine set to standard, which will change the no-fly depending on the types of dives I've done. However, many computers just have a fixed time. So, if the diver has done any dive, the time would be the same.

 

[scubadada]

I'm really tired of hearing this. It is a gross simplification, and technically incorrect unless you also specify what you mean by "deco." If by deco you mean absorbed some N2, then OK. But at the 99.9% level, what we mean by "deco" is so much N2 absorbed that it cannot be safely released. Otherwise, we could not dive at all.

Exactly. That's why I use no stop or deco dive

 

[tursiops]

What I mean is that on all (non-trivial) dives, absorbed N2 will be released during your ascent. This physiological phenomenon during the ascent is called decompression. The ascent needs to be such that excess N2 is less than your chosen limit.

For dives approaching NDL, you would exceed the limit if you teleported to the surface, but in reality you deco sufficiently during the ascent to be below the limit.

If you exceed NDL, you need to further slow the latter part of the ascent to prevent exceeding your limit while in the water, traditionally done with discrete successively shallower and longer stops. We traditionally call these dives deco dives, but in reality all (non-trivial) dives have nitrogen decompression occuring on the ascent.

A safety stop is a deco stop, it just isn't necessary to reduce N2 below the limit before surfacing.

You are trying too hard to justify a thoughtless statement, usually used as an attempt to be cute or to denigrate those who say they do not do deco dives. Unworthy; your posts are usually quite clear, concise, and on point.