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

[Joneill]

So, do you think that "emergency deco" is a good term? I wonder if any other agency uses that?

They should just call it what it is: unplanned deco!

Even as a newbie, I remember enough about NDL from tables for the expected max depth (or check tables I carry) to have a good sense of min NDL before I start the dive. Once I get to depths where NDL would start being a concern, I check my PDC regularly to ensure I've started ascending by the time my NDL hits 5 minutes. I agree that, as long as you are paying attention, you should never get to this "accidental" deco.

However, I've already seen divers do exactly that though - last trip it was a guy who was too busy chasing critters with his camera and ignored the DM's signals to ascend. Luckily he had enough air (and the boat had regs hanging at 20 feet just in case). The DM had some choice words for him topside and he was not allowed to do the second dive (and, believe it or not, he was annoyed).

 

[DevonDiver]

Logically you now have to ask for exact definition of unacceptable risk too.

Why?

The M-values selected for an algorithm defines exactly what the designer calculated as a maximum acceptable risk.

For no-stop diving, the bottom time limits reflect staying inside that acceptable risk (M-value) based on a direct, determined speed, ascent to the surface.

 

[DevonDiver]

They should just call it what it is: unplanned deco!

Unplanned deco constitutes an emergency because you have not ensured (planned) adequate gas to complete that deco.

That's the emergency.

It becomes an 'incident' when you can't complete the deco needed.

It becomes an 'accident' when failing to complete that deco results in a DCS illness.

 

[dmaziuk]

Why?

The M-values selected for an algorithm defines exactly what the designer calculated as a maximum acceptable risk.

For no-stop diving, the bottom time limits reflect staying inside that acceptable risk (M-value) based on a direct, determined speed, ascent to the surface.

So which part of that is the "why"?

What's the algorithm: DSAT? If yes, what does it mean to me diving an RGBM computer?

What was the designer's definition of acceptable? One in a million? One in bazillion trillion?

I'm sure the numbers are there somewhere, but they're not in the fine manual, what's there is "emergency decompression". OTOH not everybody gets the numbers, most students get YOUR GONNA DIE!!!

According to our leader, skipped deco is unacceptable, but only if you get bent.

 

[dmaziuk]

Unplanned deco constitutes an emergency because you have not ensured (planned) adequate gas to complete that deco.

Ensured and planned are not the same thing. You can plan, but if you fail to ensure, you better have plan B. The converse, however, is not quite as bad.

 

[Joneill]

Unplanned deco constitutes an emergency because you have not ensured (planned) adequate gas to complete that deco.

That's the emergency.

It becomes an 'incident' when you can't complete the deco needed.

It becomes an 'accident' when failing to complete that deco results in a DCS illness.

Understood - it's still sort of semantics to me. I would not really consider it a true emergency unless I did not have enough gas to complete the now required deco stops - as then I have potential big problems if I can't share air or don't have access to more air (like regs hanging from the boat at 20 feet).

Otherwise, I would just follow my computer's displayed deco plan (i.e., it would not be a big deal - though I'd be annoyed at myself for getting into that situation).

 

[dmaziuk]

I would just follow my computer's displayed deco plan (i.e., it would not be a big deal - though I'd be annoyed at myself for getting into that situation).

-- or not: you did make a conscious decision to overstay the NDL, why be annoyed now?

FWIW when I'm chasing critters with the camera and then chasing the bubbles to re-join the group, rinse, lather, repeat, I usually don' t have enough air in Al80 to go into deco. Maybe on a liveaboard...

 

[DevonDiver]

-- or not: you did make a conscious decision to overstay the NDL, why be annoyed now?

Because, in hindsight, you might quantify your behaviour as irresponsible and pointing to a lack of discipline and self-control.

And/or that you recognise your decision to overstay your intended no-stop time as evidence of an insidious creep into complacency, that you got arrogant.. and it constitutes an abandonment of the safe diving principles that you know and understood will help preserve your safety.

Or maybe angry with yourself that you ran your dive with less control and weaker procedures than might be expected of a newly graduated open water student...

 

[DevonDiver]

I would not really consider it a true emergency unless I did not have enough gas to complete the now required deco stops - as then I have potential big problems....

The emergency is due to the not knowing.

Whether it results in injury or not, does not limit the definition of emergency.

 

[DevonDiver]

Ensured and planned are not the same thing. You can plan, but if you fail to ensure, you better have plan B. The converse, however, is not quite as bad.

Plan your dive. Dive your plan.

For a responsible and prudent diver, planning is ensuring.