another question from manual

[Frosty]

Hey folks one case study has me thinking.
Senario is.--drift dive You leading and an instructor is with you. 6 certified "customer" divers
One diver uses a lot more air than normal and gets to 500psi after 25 minutes.
No issues with air checks etc
depth is roughly 24m/80 feet.Low air customer not happy with being politely asked to head up towards the surface.
Instructor escorts the diver to the surface directly ie skips safety stop.
My question is was that the best action on the part of the Instructor?

Maybee Im missing something but at 500psi I would have thought the instructor would have put the customer on his (the instructors) octi ,proceded to the safety stop then had the diver go back to their own air during the safety stop and final ascent.
What have I missed?

 

[Oldbear]

Frosty,

Quick question to shed a little more light on the scenario. The diver who took the low air diver to the surface, were they a diver/guide/dive leader with an instructor rating (as opposed to just a Divemaster rating) or were they an instructor leading a class of certified divers on a drift dive? Not sure if this ms,es a difference.

Ideally if diving at 24 meters or 80 feet a conservative dive will allow around 1000-800 psi for a safe rate ascent and a 3-5 minute safety stop at 5 meters / 15 feet. Then surface with a 500 psi reserve.

A Safety Stop is only a safe practices recommendation; an Emergency Decompression Stop is mandatory to minimize thr DCS risks. So if a Recreational Diver is diving within their NDL, a diver could go directly to the surface without the added benefit of a Safety Stop.

Your description of the scenario sounds like the diver with an instructor rating made an on the spot decision to take the low air dive directly to the surface and not do a Safety Stop while sharing sir based on:

Low air diver had a high consumption rate
Low air diver was utilizing their 500 psi surface reserve gas at depth
Low air diver still had 2-4 minutes of ascent to surface
Low air diver was diving at 24 m or 80 ft which uses gas 3.4 times as fast as at the surface
Low air diver was not in the best of moods
Low air diver was within NDL so EM Deco Stop not mandatory to minimize DCS risk
Low Air diver was on a drift dive so current should be expected all the way to surface

I might have done the same thing, but the Low Air Diver would not dive again that day or have a really long surface interval. To answer your question if the direct ascent was the BEST way to handle the situation is really hard to say on a judgement call.

 

[Basking Ridge Diver]

Two things I would say -

I would have expected the instructor to do a stop just to show the OW diver how to conduct a normal dive. It is true it is a judgement call but the norm is to make the stop for however long but recognize a stop is a good thing.

Second is I did a recent dive that was close to your profile - I left the DM and the group when I hit 700 PSI - at 30 feet I started to slow down and launched the SMB - because we were on a drift dive (Area 51). I launched and messed up - the line got caught on my gopro and I was too light with weight - it was my first drift dive and I had not been in a 3mm suit in a few months so I guessed at my weight needed. Here is my profile - I was more mad at myself for getting into that predicament but it was my first dive - 34% Nitrox and I dove the second dive. So although I learned a lesson - I was unable to hold the stop and blew it off - but that was not a normal dive for me - it was a mistake, I did not get hurt and I will be much more careful next time.

 

[oly5050user]

Why create an possible emergency situation when one does not exist?
Safety stop is optional, especially when no where near Ndl.
Having low on air diver perform a alternate air source ascent just to perform a unnecessary safety stop only adds up to a higher level of risk for all involved.

 

[Frosty]

Why create an possible emergency situation when one does not exist?
Safety stop is optional, especially when no where near Ndl.
Having low on air diver perform a alternate air source ascent just to perform a unnecessary safety stop only adds up to a higher level of risk for all involved.

Please help me out here. MY thinking was that Going to octi as a precaution during ascent would be a better option than the potential of a genuine OOA.In the same way as a safety stop is better for the body than a direct ascent.
PLEASE understand Im not argueing with you at all-just trying to get an understanding of why the direct ascent was the best option.

---------- Post added June 6th, 2015 at 09:28 AM ----------

Oldbear.-This is a case study in the DM manual. I understand it actually happened.
The "rank" of the divers was
1)6x certified divers -no indication of experience level
2) Local DM dive guide
3) instructor who organised the trip to the dive site for this group of divers.

 

[Bubble Junky]

I would've shallowed up long ago and not still been at 24m with a diver with 500 psi/35 bar !

 

[Edward3c]

I would've shallowed up long ago and not still been at 24m with a diver with 500 psi/35 bar !

Second that. Good dive management should have the diver back to the shallows before they get that low.

 

[Oldbear]

I would've shallowed up long ago and not still been at 24m with a diver with 500 psi/35 bar !

Second that. Good dive management should have the diver back to the shallows before they get that low.

I agree good dive planning and gas management should have prevented this situation in the first place.

The OP's question, however, was about a case study with some specific parameters. So back to the case study and their question concerning doing a safety stop with an alternate air.

With the given circumstances, 500 psi at 80 ft, poor attitude of low air diver, diving in current, 2-5 minutes of ascent time and about 350 psi remining useable air, I would skip the safety stop too and ascend directly to the surface. The dive has already shown they cannot manage their gas supply and do not recognize the danger they are putting themselves and possibly other divers in with their poor attitude about surfacing with 500 psi remaining. The last thing I want to do is tather myself with this diver sharing my air. Bad things usually only get worse. Again Safety Stops are optional if diver is within their NDL. Since your case study does not mention NDL remaining times, I took this as they were within the NDL.

 

[Searcaigh]

On most dives I have done with a group being lead by a DM or guide, the general rule is to inform the DM/Guide when tank is half empty e.g. that is 100 bar or 1500 psi in order to assess any change in plan.

Having a diver inform the DM/Guide that they only have 500 psi left at 80 ft is pretty poor planning

 

[Freewillow]

BAd planning or stupid diver. Your choice