Diver vs DM Responsibilities

[outofofficebrb]

The dive profiles, as stated, are so far outside tables they can’t be calculated.

It would be more useful knowing the average depth of the dives. In addition what was the surface interval.

Its easy to do 60 minutes on a 30m dive if most of the time is spent above 15m.

They probably went down to 94 ft at max depth and the total dive time was 54 minutes but who knows what depth they were at the rest of the time and for how long. Better yet, the dive profile downloaded from computer would be ideal.

 

[mcohen1021]

The tables say:

1. If NDL is exceeded by no more than 5 minutes, you have a mandatory 8 min stop @ 15 ft and out of water 6 hours.

2. If NDL is exceeded by more than 5 minutes, you have a minimum 15 min stop @ 15 ft and out of water 24 hours.

Those are both minimums IMO, and for #2, pray you don’t get bent.

I am and have been an inactive DM for many years. I still dive 3-4x / yr on vacations but not nearly as much as I did when I worked classes and did inland Texas diving… My opinion, I would have benched everyone that went into Deco for one or multiple dives, even if I risked losing them as customers.

 

[kmarks]

The tables say:

1. If NDL is exceeded by no more than 5 minutes, you have a mandatory 8 min stop @ 15 ft and out of water 6 hours.

2. If NDL is exceeded by more than 5 minutes, you have a minimum 15 min stop @ 15 ft and out of water 24 hours.

Those are both minimums IMO, and for #2, pray you don’t get bent.

I am and have been an inactive DM for many years. I still dive 3-4x / yr on vacations but not nearly as much as I did when I worked classes and did inland Texas diving… My opinion, I would have benched everyone that went into Deco for one or multiple dives, even if I risked losing them as customers.

That's on the back of the PADI card. That, combined with the knowledge that she went to 94 feet for at least some amount of time during a 54 minute dive, makes me think it was possible that she exceeded the NDL at 90+ for as much as 10 minutes. With decent SAC, she could easily have had 800 psi left after spending 35 minutes averaging 90 feet. Her computer, being more versatile than a table, would have required the 20 minute stop, and if she averaged about 30 feet from them on, she'd have just enough air to make it.

 

[boulderjohn]

The tables say:

1. If NDL is exceeded by no more than 5 minutes, you have a mandatory 8 min stop @ 15 ft and out of water 6 hours.

2. If NDL is exceeded by more than 5 minutes, you have a minimum 15 min stop @ 15 ft and out of water 24 hours.

That's only true if you are using the tables to execute your dives. If you are using a computer, you follow the algorithm of the computer.

 

[boulderjohn]

With decent SAC, she could easily have had 800 psi left after spending 35 minutes averaging 90 feet.

Diver starts with 77.4 cubic feet in an AL 80.

A SAC of 0.5 is considered to be excellent. At 95 feet, a diver with a 0.5 SAC will breathe about two cubic feet per minute. After 35 minutes, that diver will have consumed 70 cubic feet, leaving about 7 cubic feet left--less than 300 PSI. (Not all of that will be usable.) Ascending to a safety stop at 30 FPM will take nearly 3 minutes and will consume about 3 cubic feet. Before she gets there, the tank will be so low on air that the regulator will not be able to deliver it to her, at which point she will be OOA.

 

[mi000ke]

A DM's job is to follow the expectations of his or her employer. We have had countless numbers of these threads, and in some cases, dive operation owners participate. In every case I can remember, the operation's owner has said he or she expects the DMs to feel and act responsible for the safety of the divers.

I use the same small number of dive ops and generally dive with the same set of DMs, and all of them are expected by the dive operation to be responsible for the safety of the divers they are guiding. They conduct excellent pre-dive briefings, set clear limits on depth and ndl, and check on divers' air frequently during the dive. That said, I still consider them primarily to be guides, and so I take responsibility for my NDL, gas management, and for adjusting my dive as needed. I'll request we turn at our agreed on PSI if I'm there and no one else has yet, I'll signal when I'm at half tank and again at 1000 psi, or signal my intent to shallow out if needed, or signal that I'm going to do my safety stop and end my dive if I'm down to 700 psi or so. I would expect all the other divers to do the same, even though the DM is watching out for us as well.

 

[woodcarver]

The Suunto D4i gives you 3 minutes to get back under a deco ceiling and complete the obligation. If you don't, it goes into error. It will lock you out for 48 hours. While I know Suunto is known to be conservative, don't most computers lock up if a deco obligation is missed? Seems like I've seen several posts that Shearwaters don't.

 

[NorCalDM]

The Suunto D4i gives you 3 minutes to get back under a deco ceiling and complete the obligation. If you don't, it goes into error. It will lock you out for 48 hours. While I know Suunto is known to be conservative, don't most computers lock up if a deco obligation is missed? Seems like I've seen several posts that Shearwaters don't.

Yes many or most recreational computers will lock you out if you miss an obligated stop. Shearwater computers do not, being a technical based computer they probably assume you understand the risks of missing a stop.

 

[Blasto]

Scenario: Diver with less than 100 dives. Dives exclusively with the same divemaster each trip. Her husband is a much more experienced diver. Everyone using computers.

100 dives is far too little experience for self-taught deco diving. (Different rules when professionally trained and qualified - I know more than one person whose first open water dive was an accelerated deco dive). Having a tec trained buddy doesn't resolve the issue, as it turns buddy separation into a life-threatening emergency. If done in recreational gear, this isn't deco diving, it's stupid diving.

1. As her DM, do you make her stay out of the water for 24 hours based on that 20 min deco stop? (translation: fall back to the PADI dive tables rules)

Depends on which capacity I'm working in. Is this a dive shop operation or am I an independent dive guide for hire?

In the former case, definitely. They're breaking the rules and placing liability on the dive op, it's the DM's duty to prevent that.
In the latter case, it's up to the DM to decide if they're comfortable looking after someone putting themselves in danger.

As for points 2 and 3, they raise the issue to a level where, if there was an actual problem, even a tec trained and geared DM's ability to help is being stretched past capacity, since so many divers are one misstep away from a life-threatening situation and things often go wrong in a cascade.

Going to 20 minutes of deco would call for more than a sit-out. Making a Suunto show you a couple minutes of ceiling is not a problem, that's just a mandated safety stop. But 20 minutes on any computer indicates a genuine deco obligation, which can't be safely completed without fully redundant equipment and relevant skills. Unless forced deco was caused by an emergency, vacation divers at this point need remedial training, not dive supervision.

So it's not really a question of tables or computers. If the divers were lucky enough to complete their deco on single tanks without blowing stops, their bodies are fine. It's not 6 or 24 or 48 hours they need to get back into the water, but an attitude adjustment. The margin of safety in rec gear is razor-thin and vanishes if more than one diver violates rec diving assumptions.

 

[Marie13]

The Suunto D4i gives you 3 minutes to get back under a deco ceiling and complete the obligation. If you don't, it goes into error. It will lock you out for 48 hours. While I know Suunto is known to be conservative, don't most computers lock up if a deco obligation is missed? Seems like I've seen several posts that Shearwaters don't.

Shearwaters do not. Remember they were originally intended as tech diving computers, only recently more aimed at rec divers.

I seem to remember reading somewhere here that Geo 2.0 will not lock you out, but I couldn’t be sure on that.