Drop Tanks - Where do the responsibilities lie?

[Diving Dubai]

I would suggest drop tanks use is outside the scope of the American definition of recreational diving

No. It's inside the scope.

On dive #3 of the Deep diver course:- "The Student divers perform an 8-minute simulated emergency decompression
stop while breathing from an emergency air source for at least one minute."

The need for the 8 min emergency deco stop is a carry over from tables.

That said, often for some students it's a tricky little skill, requiring them to maintain buoyancy while task loaded at a stop.

A high proportion of dive centres especially where their main customers are vacation divers, place a drop tank near teh line on deeper sites.

Thus its a requirement to teach DM's how to rig one. On my DM course the frequently used cylinder is of course pre rigged in a stage sling, so one exercise simulates that cylinder being out of service and them having to cobble together a rigging kit from stuff on the boat. This exercise while simulating a likely real life event, also teaches and reinforces their abilities to problem solve and safely carry carry out non routine tasks.

So while the points you make are fair, the requirement for DM's to have the knowledge and experience to rig a drop tank are certainly within the scope of recreational diving.

 

[Gareth J]

No. It's inside the scope.

On dive #3 of the Deep diver course:- "The Student divers perform an 8-minute simulated emergency decompression
stop while breathing from an emergency air source for at least one minute."

The need for the 8 min emergency deco stop is a carry over from tables.

That said, often for some students it's a tricky little skill, requiring them to maintain buoyancy while task loaded at a stop.

A high proportion of dive centres especially where their main customers are vacation divers, place a drop tank near teh line on deeper sites.

Thus its a requirement to teach DM's how to rig one. On my DM course the frequently used cylinder is of course pre rigged in a stage sling, so one exercise simulates that cylinder being out of service and them having to cobble together a rigging kit from stuff on the boat. This exercise while simulating a likely real life event, also teaches and reinforces their abilities to problem solve and safely carry carry out non routine tasks.

So while the points you make are fair, the requirement for DM's to have the knowledge and experience to rig a drop tank are certainly within the scope of recreational diving.

Thanks for the overview.

I know when I've dived in the Red Sea on wrecks like the Thistlegorm, they leave a stage cylinder suspended from the stern of most of the dive boats as a just incase.

When I used to do bits for my local shop/school. A lot of the Students would complete Rescue Diver then look to crossover to BSAC Dive Leader. Completing DL was a quick way to get a diving qualification that covered decompression. This was before Nitrox had made its way into the mainstream.
Most of the students that continued to dive basically dived the DL qualification for flexibility. Mainly because so much of the UK diving was likely to involve some decompression on a regular basis.
There is hardly any point going to somewhere like Scapa Flow if you can't do some decompression if you want to get the best out of the experience.

 

[boulderjohn]

I understand that according to PADI standards drop tanks should be used when doing deep dives and its the responsibility of the most qualified diver on board, in my case the instructor, to notify the Boat Captain that they will be needed.

As a DM candidate, you are expected to know PADI standards, or be able to find a relevant standard. Can you find and quote the standard that says "drop tanks should be used when doing deep dives and its the responsibility of the most qualified diver on board, in my case the instructor, to notify the Boat Captain that they will be needed." I don't know that standard myself.

In this situation, as the DM trainee, I was instructed to tell the Boat Captain that we would be needing a drop tank, which I did, also adding to check the regulator was working ok and that he had enough rope to hang it at 5 meters.

Next, here are all the Deep Dive Scenario standards from the PADI manual:

Skill 5 — Deep Dive Scenario
Conduct a deep dive in which each divemaster candidate
completes the following:
• With a buddy before the dive, prepare emergency
breathing equipment, and position it at the safety
stop depth.
• Descend using a reference line, wall or sloping
bottom as a visual guide only, while staying with a
buddy and controlling the descent rate.
• Navigate with a compass at least 20 kick cycles away
from and back to the reference line or designated
spot.
• Use a depth gauge and timing device, or a dive
computer to monitor an ascent rate no faster than
18 metres/60 feet per minute while using a reference
line, wall or sloping bottom as a visual guide only.
• Perform a 3-minute safety stop at 5 metres/15 feet
before surfacing without holding on to a reference
line for positioning.​

The standard calls for the DM candidate to "prepare emergency breathing equipment, and position it at the safety stop depth." As I read it, you were supposed to place the hang tank, not the boat captain.

 

[boulderjohn]

On dive #3 of the Deep diver course:- "The Student divers perform an 8-minute simulated emergency decompression
stop while breathing from an emergency air source for at least one minute."
...
That said, often for some students it's a tricky little skill, requiring them to maintain buoyancy while task loaded at a stop.

This is the standard from the Deep Dive specialty course, not the deep dive scenario from the DM course.

That standard calls for the student to breathe from an emergency air source for at least one minute. It does not define that emergency air source, and it allows many options. For example, the candidate could breathe from a buddy's alternate air source, use his or her pony bottle if carrying one, or take a buddy's pony bottle.

Here is the only similar requirement in the DM Deep Diver Scenario:

• Perform a 3-minute safety stop at 5 metres/15 feet
before surfacing without holding on to a reference
line for positioning.​

 

[wetb4igetinthewater]

I have nothing to add, other than to say excellent discussion with great information from @Diving Dubai and @boulderjohn.

@Nudibranch Diver, I hope you find another path to achieve your goals. Sorry that you had to deal with such a mess.

 

[rongoodman]

tlegorm, they leave a stage cylinder suspended from the stern of most of the dive boats as a just incase.

I think every liveaboard I've ever been on does the same, no matter the location.

 

[Bob DBF]

The need for the 8 min emergency deco stop is a carry over from tables.

That would be the PADI DSAT tables, rather than the earlier PADI Navy tables which were extended on the slate so that one could calculate one's decompression stop if one overstayed their bottom time. I used the Navy tables when I started diving, and picked up the PADI Navy tables slate in 1980, and used it until I purchased a dive computer.

 

[Gareth J]

I think every liveaboard I've ever been on does the same, no matter the location.

I should be in the Shetland Isles in a fortnight. I can guarantee there won't be a drop tank suspended over the stern there. The boats never moor into the site.
If there is to be a drop tank, we will have to take our own and rig it. Either as a drop tank with its own buoy, or as a stage to be secure to the shot by the second pair.
(All the deco is likely to be under 30 minutes, so we are unlike to put a stage in. Also, I suspect there will be a lot of tidal movement, so getting back to the shot is probably not a practical option.)

 

[Centrals]

The standard calls for the DM candidate to "prepare emergency breathing equipment, and position it at the safety stop depth." As I read it, you were supposed to place the hang tank, not the boat captain.

The instructor should had discussed with the DM candidate on the purpose of the dive FIRST!

 

[boulderjohn]

The instructor should had discussed with the DM candidate on the purpose of the dive FIRST!

I think they did discuss it first. It would be interesting to hear what was said in that discussion.

If the DM candidate goes on to become a DM on a boat that uses a drop tank, it will likely be his job to drop it, as assigned by the captain. That is why it is a training requirement.