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Using the min deco table
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How to use the Minimum Deco Table.

The Minimum Deco Table was designed to be easy to use and compact! If you print out the pdf you can laminate it and put it in your wetnotes.

Use it for repetitive diving in the 0-120ft (0-36m) range using standard gases. It's based on the same algorithm as GUE's Decoplanner/DPlan - Buhlmann ZH-L16B with gradient factors.

This guide is for the imperial version but the metric version works the same.

Deep stops.

The table has a couple of stops that you are supposed to do everytime to minimize bubbles. It's also an excellent idea to add a deep stops in addition to what the table recommends. Since the table's first stop is at 40ft/12m all you have to do is add 1-2 minutes at 50ft/15m - if you dive to 100ft/30m that is.

GUE recommends doing 1 minute stops from 50% of the maximum depth and then every 10ft / 3m up to the surface. NAUI recommends doing 1-2 minutes at 50% of the maximum depth and then a regular safety stop.

Now let's go plan some dives!

1. Plan the first dive.

Let's say we want to dive a reef and the maximum depth is 60ft.
We dive a standard 32% nitrox mix. How long can we stay?

 
Diving with a bottomtimer & tables.

It's a very good idea to write down the maximum times in your wetnotes. Now you can modify the dive plan during the dive. Try to memorize them as well, it's not too difficult.

The first dive:

120ft 25 min
100ft 35 min
80ft 50 min
60ft 85 min
50ft 160 min


Well, first we find the depth and then we look for the maximum time.
In this case we can do 60ft for 85 minutes and after that we do the mandatory stops.



2. Plan a second repetitive dive.

Suppose we want to make a second dive.
Since we already have some nitrogen in us this is a bit more complicated.
Let's say our first dive actually turned out to be 60ft for 60 minutes.


First we find the depth/time and then the group, which is Group E.

Now, after the first dive it took us 45 minutes to change tanks and prepare for the second dive. What group does that put us in?

 
What does Group E really mean?

The group letter represents an amount of nitrogen and we need to keep track of that for repetitive diving. For example, if you do two repetitive dives and finally end up in Group E. That means you have the same amount of nitrogen as you would if you only did one dive to 60ft for 65 minutes, or 80ft for 40 minutes etc.

Well, the Surface Interval table says -2 for 30 minutes and -4 for 1 hour.
Since 45 minutes isn't one hour we use 30 minutes.
That means that we go 2 groups to the left of E which is Group C.

So if we plan on doing a dive to 60ft again, how long can we stay?

Well, 60ft and Group C means that we have the same amount of nitrogen as a "60ft for 45 minute" dive. So we can stay 85-45 = 40 minutes at 60ft.
Do you see it says 40 in small numbers? That's the same number we calculated above, the remaining bottomtime.
 
The second dive can be (group C):

120ft 10 min *
100ft 15 min
80ft 25 min
60ft 40 min
50ft 100 min

Write it down in your wetnotes!

* we would need 30/30 triox for this.


3. Plan a third repetitive dive.

Let's say we did 50ft for 50 minutes as our second dive.
Does that put us in group C???

Well, no becuse we have to consider the nitrogen that is already in us.

We were in Group C which means we have to add 60 minutes to our bottomtime.
We get 60+50 = 110 minutes which puts us in Group F.
So if we do two hours on the surface what group are we in?


Well, we became Group A.
And if we look at group A we can easily find how long we can stay for the third dive.

The third dive can be (group A):

120ft 17 min *
100ft 25 min
80ft 40 min
60ft 60 min
50ft 130 min

Write it down in your wetnotes!

* we would need 30/30 triox for this.



4. Plan a fourth repetitive dive.

Just repeat the same process as we did in dive three...


5. Conclusion.

Now you know how to use the Minimum Deco Table!

Remember!

  • Always do the mandatory deco stops no matter what depth or duration of your dive
  • If you dive to 100ft/30m add an additional deep stop at 50ft / 15m
  • Never ascend faster than 30ft/min, especially the last 20 feet.
  • When you must dive on air - use the air depths instead.
  • The table is designed for up to four dives per day.

Happy Diving!!!

Peter


This page was last modified 23 March 2013
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