Reasons to do "Minimum Deco"

[Reg Braithwaite]

"Minimum Deco" is the most common name given for a practice of making a very slow (10ft or 3m per minute) ascent from approximately one half of your average depth on dives that most people would call "No Deco" dives. Another name you'll see is "One Minute Ascents" (which I find incredibly misleading since you take much longer than a minute to make the complete ascent!

The usual practice is to stop for about thirty seconds and take 30 seconds to ascend 10ft/3m, stop for thirty seconds, and so forth. On another thread, some asked why it was worth the bother...

To the OP, why so many stops(ie 30,20,& 10) for this dive??.....Also, where was your buddy(or another diver on the dive) ie look @ someone else's gauges??.....

A lot of work for little reason, no??

Reasons I choose to do Minimum Deco (or something approximating it):

• Provided that conditions are pleasant, off-gassing in the water is better than off-gassing on the surface.
• If I overstay my welcome and need to do some actual deco, I already know how to do it, I just need to adjust my schedule.
• A n00b like myself can never have too much practice maintaining level trim at a constant depth without kicking.
• I paid for a full tank of gas, why not use it?
• There's something meditative about hanging stationary and weightless. Why pay a yoga studio for the experience?
• I'm also "trained" for recreational trimix diving, which is much less forgiving of fast ascents and blowing off "safety" stops. Why not use one protocol for all of my dives?
• You can never have too much practice launching an SMB and keeping the line from wrapping around your throat. Especially if your 'home turf' is the swift running St. Lawrence River.
• Anecdotally, reduces sub-clinical DCS instances without the expense and hassle of diving nitrox. Combine with nitrox for ridiculously safe diving.

That being said, on drift dives you really want to stay with the group. If they're following the "standard" protocol, you have to start your deco before they do to surface in the same place at the same time. Also, in certain situations you can drift into trouble while doing minimal deco on an SMB, like a shipping channel. You have to plan accordingly and maybe do your deco on a wall or while swimming gently to navigate appropriately.

On several dives in Cozumel I bailed a little early and did my first couple of stops swimming slowly above the group while observing them poking around the reef from above. They then ascended to 15' while I was at 20' and everything worked out just fine.

Bailing early is also only appropriate if you are comfortable doing this solo. In the St. Lawrence, I am not. In Cozumel, I was.

 

[DCBC]

So Reg, you're against traditional emergency stops?

 

[Atomic_Diver]

isin't that practically Saturation deco, or at least kinda similar to, as supposed to the USN Saturation schedules of like a few feet per hour....?

 

[DCBC]

isin't that practically Saturation deco, or at least kinda similar to, as supposed to the USN Saturation schedules of like a few feet per hour....?

There are tons of saturation tables and they really vary. The one I prefer has a 1 fpm ascent, a stop for 1 (later 2 mins) every 10' between the slated decompression stops. The thing with saturation is that each company has their own profiles to follow.

 

[nilsdiver]

isin't that practically Saturation deco, or at least kinda similar to, as supposed to the USN Saturation schedules of like a few feet per hour....?

Saturation deco requires "maximum deco". The most deco you need to ascend from depth. "Minimum deco" is on the other end. You never do less then minimum deco for no deco dives.

 

[TSandM]

The origin of "minimum deco" is from two ideas: One, that ALL dives are decompression dives, in the sense that ongassing and offgassing occurs on all dives, and divers should be taught from the beginning to control their ascents and to be able to do stops. The second thing is that the NDLs for GUE divers are based on running Decoplanner and coming up with the times that would generate a deco schedule of one minute stops from half maximal depth. So the NDLs and minimum deco go together.

 

[JeffG]

The second thing is that the NDLs for GUE divers are based on running Decoplanner and coming up with the times that would generate a deco schedule of one minute stops from half maximal depth. So the NDLs and minimum deco go together.

Really?

and here I thought it was because the min deco creates a better dive profile (with ~ the same run time) as the standard dive with a PADI safety stop.

I didn't realize it was because the used decoplanner.

 

[Crowley]

I'm not sure this is appropriate to "Basic" scuba discussions, but in the "basic" world of recreational diving, I think the benefits would be so minor as to be statistically unmeasurable. The OP talks of "anecdotal evidence" about improving safety but I hear of no such anecdotes in the enviroment in which I work - which has hundreds of thousands of divers every year. There's a similar post in the advanced forum about the benfits of decompressing uses hyperoxic mixes at different points during ascent.

There's plenty of research available about the benefits of ascent rate versus depth and dive time etc and in some cases, slow ascents seem to marginally increase nitrogen loading in the body, whereas a good old safety stop at 5 metres so dramatically reduces the nitrogen load that ascent rate (within a given timeframe) is almost meaningless. Safety Stops are not a PADI invention, it's well proven theory taught by pretty much everybody.

The argument that all dives are deco dives is of course literally correct, but recreational diving has been developed so that a direct ascent to the surface is possible at all times with minimal risk of the bends. Some argue that the safety stop is a decompression stop, and yes, of course it is, but it's not as mandatory (according to the data) as it is in the realms of Tec diving, safety stop versus deco stop is a matter of semantics, but I think we have well established difference between recreational diving where you make a safety stop and full on decompression diving.

As I said in the hyperoxic washout thread in the advanced forum - for recreational diving it would simply be impossible to teach. For those who are interested in diving on trimix and full tec diving, there are plenty of courses available.

My 2 cents

C.

 

[paddler3d]

I need a bit of help understanding the 'Min Deco' thing.

On Dir-Diver.com I found a table for Min Deco using EAN 30-32%.

At 120ft it give you 25min and you have a 1min stop at 40, 1min stop at 30, 3min stop at 20, 3min stop at 10 and no faster than 30fpm ascension rate.

I have a NOAA 32% table in front of me.

At 120ft it gives me 25mins as the NDL.

So without doing some repetitive dive scenarios here, what is the advantage/disadvantage of one over the other?

I know slower is better and it never hurts to hang at your SS longer than what your watch says.

The min deco seems to be a bit excessive?

 

[Reg Braithwaite]

I'm not sure this is appropriate to "Basic" scuba discussions...

Why ever not? What is more basic than how to plan a dive, how to dive a plan, and why?

The OP talks of "anecdotal evidence" about improving safety but I hear of no such anecdotes in the enviroment in which I work - which has hundreds of thousands of divers every year.

To be precise, I said:

Anecdotally, reduces sub-clinical DCS instances

And I will provide the anecdotes. I log my dives and I log when I have any of the following in the 24 hours after a dive: Excessive tiredness, muscle soreness, aching joints, or a runny nose. Back when I was a distance athlete, such things were signs that my immune system was run down and that I was over-training. With diving, I associate them with the possibility that bubbles in my blood are provoking my immune system into a response.

The last time I was hit by this after diving was a day I did four dives in one day on Nitrox, using a single deep stop on dives over 60' and standard PADI safety stops. I was using a Suuntu Gecko to control my dives. On the fourth dive, I was within my NDL when I started to ascend, but when I stopped half way up for a minute, it put me in deco. I later suffered all four symptoms.

I subsequently switched to "minimal deco" and so far, so good. That being said, "The plural of anecdote is not data."