Depth: 95 ft, In Deco, 500 psi, No Buddy

[Dizzi Lizzi]

OK I'm that new diver and I totally get what DD is telling me. Never get there unexpectedly, but if you do, don't panic. I will remember this post. Panic makes anything worse.

 

[Kevrumbo]

What to do in this type of situation?

On a recent lobster dive I happened to capture my computer readings and gas pressure readings for the end of my dive. I pushed the no-deco limits to catch a lobster, wound the “clock” down to ZERO minutes leaving me ZERO No Deco Time. Then, as soon as I started my ascent, the computer kicked me into a REQUIRED Decompression Dive.

My gas pressure at this time is about 500 psi (in a 108 cu-ft, steel tank).

Certainly it is NOT recommended or safe for recreational divers to push the limits or go into deco and they probably should be saving more air for the ascent as well. Many people are taught the simplistic rule of: be on the boat with 500 psi – which may be inadequate.

The reason I made a video of the ascent is to demonstrate that this is NOT the time to panic or get really worried, or rush your ascent, or kick up hard or begin to breathe fast or get overly stressed out.

We have many examples of divers who have never seen their computer in deco and once it happens they kinda freak out and rush to the surface – breathing like a freight train. Sometimes I think they feel their goal is to get on the boat with as close to 500 psi as possible – so the faster they rush to the surface the less “trouble they are going to be in”. This is NOT the way to handle such a situation. (Most instructors would say that the best way to handle this situation is to avoid it, but that is not the point).

This video demonstrates what I do (or did on this occasion) in this situation. Keep in mind that the deco penalty is as small as it can be (only one minute), but many people would be very concerned by “being in true DECO” and also having just 500 psi at around 100 ft depth.

Instead of exerting myself, you can hear me pop the inflator and get just slightly buoyant so I can drift slowly upward with zero kicking. I slow my breathing and RELAX. I go up SLOW, I check my depth frequently and carefully monitor my ascent rate.

This video is in real time (except for the pauses during the console reading). By the time I reach a depth of about 44 ft (I think it is) – Wow.. my deco penalty is gone - and I have many minutes of no deco time back on my computer.

This is not surprising to a good percentage of experienced divers.. come up a little slower than the maximum ascent rate, relax and your deco time will “clear itself” before you even get close to the decompression ceiling depth. For them, the video will be trivial and boring (maybe that is the point of the video).

My objective in posting this is NOT to advocate or recommend that any recreational diver put themselves in deco and they certainly should preserve a safe volume of gas for their ascent (and enough to share with a buddy). My goal is to provide a simple example that if you (unintentionally) go a little into deco, it is possible to make an ascent using a modest amount of gas, do it reasonably safely and this is NOT THE TIME TO RUSH TO THE SURFACE.

For this dive, I was alone – so I had no need to reserve air for a buddy, I had an independent bail out bottle (a pony bottle) as a back up and I was not diving in an aggressive or reckless manner. I continued a slow ascent and completed an additional safety stop on this dive (as I do on almost every dive) and exited the water with a few hundred psi remaining (and a full pony bottle).

Making an ascent from this depth while sharing air with a panicked buddy and having to exert yourself would result in air consumption rates that would be 5 or 10 times higher than shown in this video, so please don’t interpret this as a suggestion that people should be starting their ascents from 100 ft with 500 psi! The objective is to show what it might look like if you over-stay “your welcome” for a few moments and how it might be handled – even if you have not reserved a whole lot of air.

Since the intended audience is inexperienced recreational divers, it is also very important to remind them that if they continue to remain at depth (once the computer kicks into deco), the penalties (i.e., true deco time) will accrue quickly and a 1 minute deco stop can turn into a 5 or 10 minute stop faster than you can catch a lobster… Especially if you are silly enough to do this on the 3rd dive of the day. This can be a serious or life threatening situation if you don’t have the gas and skills to deal with decompression.

Maybe others will find the topic useful?

Opening Night & Weekend of SoCal Lobster Season, this is the typical disastrous predicament of the novice or infrequent/out-of-practice diver (buddy separation with no redundant pony bottle, wetsuit compression at deep depth with additional weighting of a full lobster catch bag)- all leading to a dive accident casualty.

The better take away lesson is to learn how to properly calculate & follow a gas mangement plan & ascent strategy within NDL limits without encroaching on "Rock Bottom" gas margins (i.e. 95', 500psi remaining, potential mandatory/accruing deco stop condition and no buddy) requiring gas-sharing with a buddy, or in this case near imminent contingency deployment of a pony bottle.

How to calculate and follow a minimum gas reserve contingency and ascent strategy for a buddy dive team:

 

[EricTheDood]

The better take away lesson is to learn how to properly calculate & follow a gas mangement plan & ascent strategy within NDL limits without encroaching on or going far beyond "Rock Bottom" gas margins

Those who are more likely to screw up underwater are less likely to spend time and effort in planning.

In other words, people who sift through these posts and take initiative to learn more about gas planning probably aren't the ones who were going to find themselves in deco with low air anyway.

 

[uncfnp]

Since this is presentated as a learning experience for divers...

Study: Lobster chase can hike dive-death risk


Snip...


"Failure to monitor the remaining air in a dive tank emerged as a big factor. Researchers followed 1,000 divers and then questioned those who came up with less than 350 PSI of air (dive crews insist divers be back on the boat with at least 500 PSI).

Hunting divers were “20 times more likely to be surprised by how little [breathing] gas they had at the end,” Buzzacott said. “It wasn’t because they went deeper or used a smaller tank. They just were not watching their gauges because they were distracted.”

 

[Steve_C]

Since this is presentated as a learning experience for divers...

Study: Lobster chase can hike dive-death risk


Snip...


"Failure to monitor the remaining air in a dive tank emerged as a big factor. Researchers followed 1,000 divers and then questioned those who came up with less than 350 PSI of air (dive crews insist divers be back on the boat with at least 500 PSI).

Hunting divers were “20 times more likely to be surprised by how little [breathing] gas they had at the end,” Buzzacott said. “It wasn’t because they went deeper or used a smaller tank. They just were not watching their gauges because they were distracted.”

Same for tooth hunters on the fossil ledges. Crews say they see more OOA there.

 

[noj3333]

As a new diver I value DD’s video, and appreciate him sharing it. I’m not going to recreate his dive, however I will learn from some of his skills and the experience he shared. The floating assent was a small bit of knowledge, as was the fact that computers can/ will clear their deco requirement if you ‘make them happy’ on your assent.

With all my diving done exclusively on vacation (so far, getting geared up for local diving come next summer) I can see why some dives would rush to the surface… that universal rule all DM’s share with you, “If you go into deco on the first dive, you’ll have to sit out the second dive”. Clearly this is no logical reason to rush you assent, but as a new diver it’s good to hear your computer can/ will clear itself if the conditions are right (allowing you to have a safe assent, and enjoy your second dive).

Side note, am I correct in saying DD did NOT go into deco, due to his actions once he ran out of NDL time?? Thus the, 'deco on your first dive = no second dive' rule would NOT apply to him??

 

[Steve_C]

Never heard the deco = no second dive rule. Had a DM lead me into light deco on dive 2. Cleared computer with 10 minute + safety stop. Hour or so later she took me on a drift dive starting at 70. Stayed within NDL but had to go high. Did a shallow 4th dive later. This was with a Suunto.

This is assuming that you cleared your computer during the assent + safety stop otherwise computer is likely to get ticked and lock you out.

Going back out of deco depends on the computer, the asseent, and some other information. Some give you time back quicker than others do. But even with a suunto it can happen.

 

[Basking Ridge Diver]

Side note, am I correct in saying DD did NOT go into deco, due to his actions once he ran out of NDL time?? Thus the, 'deco on your first dive = no second dive' rule would NOT apply to him??

If you are referring to the PADI tables - yes that is true. Tables are very black and white when it comes to diving.

That said you are fairly new to Scubaboard and may not recognize that DD is/was an instructor. DD was sharing a story and was wearing a PDC - if you clear your PDC then of course these "rules" don't apply. But given you have 0 to 24 dives please dive within your training and your experience.

Safe Diving -

 

[dumpsterDiver]

As a new diver I value DD’s video, and appreciate him sharing it. I’m not going to recreate his dive, however I will learn from some of his skills and the experience he shared. The floating assent was a small bit of knowledge, as was the fact that computers can/ will clear their deco requirement if you ‘make them happy’ on your assent.

With all my diving done exclusively on vacation (so far, getting geared up for local diving come next summer) I can see why some dives would rush to the surface… that universal rule all DM’s share with you, “If you go into deco on the first dive, you’ll have to sit out the second dive”. Clearly this is no logical reason to rush you assent, but as a new diver it’s good to hear your computer can/ will clear itself if the conditions are right (allowing you to have a safe assent, and enjoy your second dive).

Side note, am I correct in saying DD did NOT go into deco, due to his actions once he ran out of NDL time?? Thus the, 'deco on your first dive = no second dive' rule would NOT apply to him??

No you are incorrect. If you reread the original description, you will see that i did go into deco, but had only one minute of required decompression.

The divemaster's rule of no second dive if you go into decompression, is based more on the idea that if you are too irresponsible to watch your dive time, then we aren't going to let you do a second dive. You should understand that the computer and decompression programs etc. provide very exact numbers, but they are really just rough estimates. So running your time up to having just one minute of No Deco time versus having one minute of actual deco time is not (for practical purposes) a huge difference.

This sort of binary thinking of being either in or out of decompression (as you approach the limits) is overly simplistic and not very useful. In other words, if you extend your dive to having just 2-3 minutes of remaining no deco time, you really need to make a careful and controlled ascent- not so different than if you were in "true" deco- especially if you are not as thin and young as you used to be (who is)?

Again, I am not advocating for recreational divers to go over the limit and step into actual deco, but tip toeing around the fuzzy line ain't so safe either.

 

[lowviz]

...//.. these "rules" don't apply. ...//...

...//... Thus the, 'deco on your first dive = no second dive' rule would NOT apply to him??

This is Accidents and Incidents and Lessons Learned. It covers the whole spectrum from the newest of divers to the almighty few.

In this case, "Different rules apply". (After Hours, 1985)