Decompression Dive Plan

Decompression dive planning in Kenozooid is supported with the plan deco command.

For example, to plan decompression dive

  • with EAN27 bottom gas mix

  • with EAN50 decompression gas mix

  • to maximum depth of 42 meters

  • for 25 minutes

use command:

$ kz plan deco 'ean27 ean50' 42 25

To change the dive plan parameters to

  • respiratory volume minute 16l/min (default 20l/min)

  • gradient factors low 20% and high 90% (default 30% and 85%)

  • last decompression stop at 6m (default 3m)

we can use the command:

$ kz plan deco --rmv 16 -gl 20 -gh 90 -6 'ean27 ean50' 42 25

or to specify gas mix switch depth in explicit way:

$ kz plan deco --rmv 16 -gl 20 -gh 90 -6 'ean27@0 ean50@22' 42 25

Decompression dive plan generated with above command is

Dive Profile Summary
--------------------
============================== ====== ====== ====== ======
 Name                            P      LG     E     E+LG
============================== ====== ====== ====== ======
Depth [m]                          42     42     47     47
Bottom Time [min]                  25     25     28     28
Descent Time [min]                2.1    2.1    2.4    2.4
Total Decompression Time [min]     14     20     25     38
Total Dive Time [min]              41     47     56     69
O2 Pressure of Bottom Gas Mix    1.40   1.40   1.54   1.54
MOD for Bottom Gas Mix             42     42     42     42
============================== ====== ====== ====== ======


Gas Logistics
-------------
============================== ====== ====== ====== ======
Gas Mix                          P      LG     E     E+LG
============================== ====== ====== ====== ======
Gas Mix EAN27 [liter]            3216   2731   2703   3764
Gas Mix EAN50 [liter]             644   xx      709   xx  
============================== ====== ====== ====== ======

Dive Slates
-----------
Profile *planned*::

       D  DT   RT GAS    
    ------------------------
    * 42       25 EAN27
    * 22       27 EAN50
      18   1   28 
      15   1   30 
      12   1   31 
       9   1   32 
       6   8   41 
       0       41 

Profile *lost gas*::

       D  DT   RT GAS    
    ------------------------
    * 42       25 EAN27
      18   1   28 
      15   1   30 
      12   1   31 
       9   2   33 
       6  13   47 
       0       47 

Profile *extended*::

       D  DT   RT GAS    
    ------------------------
    * 47       28 EAN27
      24   1   31 
    * 21   1   33 EAN50
      18   1   34 
      15   1   35 
      12   1   36 
       9   2   39 
       6  16   55 
       0       56 

Profile *extended + lost gas*::

       D  DT   RT GAS    
    ------------------------
    * 47       28 EAN27
      24   1   31 
      21   1   33 
      18   1   34 
      15   1   35 
      12   2   37 
       9   4   42 
       6  26   68 
       0       69 

Parameters
----------
============================== =======
Parameter                       Value
============================== =======
RMV [l/min]                        16
Last stop at 6m                 True
GF Low                             20%
GF High                            90%
============================== =======

The dive plan output is in reStructuredText format and can be simply printed or converted to many formats like PDF or HTML.

The decompression dive plan input and the details of its output are discussed in the following sections.

Dive Plan Input

Dive plan input requires three mandatory arguments

  • gas mix list

  • dive maximum depth in meters

  • bottom time in minutes

The dive maximum depth and bottom time arguments shall require no explanation.

The gas mix list is space separated list of gas mix names

  • optional travel gas mix

  • mandatory bottom gas mix

  • optional decompression gas mix

The gas mix name is case insensitive and can be

air

Air gas mix, set to 21% oxygen and 79% nitrogen.

o2

Gas mix with 100% oxygen.

eanOO

Nitrox gas mix with OO oxygen percentage, for example EAN27, EAN50.

txOO/HE

Trimix gas mix with OO oxygen percentage and HE helium percentage, for example TX21/35, TX18/45, TX15/55.

To specify gas mix switch depth with its name add @D suffix where D is the depth, for example EAN50@22 is gas mix to be switched to at 22 meters.

Travel gas mix name has + prefix, for example +EAN32@0 or +EAN32 is EAN32 travel gas mix to be used from surface.

Dive Plan Overview

A decompression dive plan consists of

  • dive plan summary

  • gas mix logistics information

  • dive slates

  • dive plan parameters

The plan is prepared for planned dive profile and three emergency situations, which gives four dive profiles in total

P

Planned dive profile.

LG

Emergency dive profile for lost decompression gas situation.

E

Emergency dive profile for extended dive situation, this is deeper and longer dive. By default, extended dive profile is 5m deeper and 3 minutes longer.

E+LG

Emergency dive profile for both extended and lost decompression gas situations.

Example of dive plan summary

Name

P

LG

E

E+LG

Depth [m]

42

42

47

47

Bottom Time [min]

25

25

28

28

Descent Time [min]

2.1

2.1

2.4

2.4

Total Decompression Time [min]

14

20

25

38

Total Dive Time [min]

41

47

56

69

O2 Pressure of Bottom Gas Mix

1.40

1.40

1.54

1.54

MOD for Bottom Gas Mix

42

42

42

42

Dive Slates

Kenozooid creates a dive slate for each dive profile, which consists of four columns

D

Dive depth [meter]. The depth is prefixed with * on gas mix change at given depth.

DT

Decompression stop time [min].

RT

Dive run time [min].

GAS

Gas mix information.

The dive slates can be written down or printed, then laminated and with added bungee can be put on diver’s forearm.

Example of dive slate for planned dive profile:

   D  DT   RT GAS
------------------------
* 42       25 EAN27
* 22       27 EAN50
  18   1   28
  15   1   30
  12   1   31
   9   1   32
   6   8   41
   0       41

Gas Mix Logistics

Gas mix logistics information provides diver with volume of each gas mix required during each of dive profiles of a decompression dive. The volume is calculated using 20l/min respiratory minute volume (RMV) by default and is expressed in liters.

The gas mix volume for planned dive profile is calculated using rule of thirds. For example, if 2000 liters of bottom gas mix is to be consumed by a diver during planned dive profile, then dive cylinder setup holding 3000 liters of the gas mix is required.

Having gas mix volume value, we can calculate if diving cylinder setup is sufficient for a dive. For example, if 1600 liters of decompression gas mix is required and we have choice of using 7 liter or 10 liter cylinder, then we can calculate required pressure in each cylinder:

1600 / 7  = 229
1600 / 10 = 160

and we should decide to take 10 liter cylinder for the dive.

NOTE: The emergency dive profiles gas mix volume information is calculated as is, this is without rule of thirds.

Example of gas mix logistics information

Gas Mix

P

LG

E

E+LG

Gas Mix EAN27 [liter]

3216

2731

2703

3764

Gas Mix EAN50 [liter]

644

xx

709

xx

Above example shows that we need at least 3216 liters of EAN27 for planned dive profile (we will consume 2144 liters of gas mix). For any emergency dive profile we need no more than 3764 liters of the gas mix.

Dive Calculators

Kenozooid’s dive calculators can be useful for dive planning, when maximum operating depth (MOD), equivalent air depth (EAD), respiratory minute volume (RMV) or other information (i.e. PPO2) is required.

Calculator commands are grouped with calc word - invoke kz calc -h to list all calculators.

To calculate MOD when breathing EAN 32 (PPO2 1.4 by default):

$ kz calc mod 32
33.75

To calculate MOD when breathing EAN 32 for PPO2 1.6:

$ kz calc mod 1.6 32
40.00

To calculate EAD for 30m when breating EAN 32:

$ kz calc ead 30 32
24.43

To calculate PPO2 for 30m when breathing EAN 32:

$ kz calc ppO2 30 32
1.28

To calculate RMV for a 55 minutes dive with average depth of 16.2m (15l tank, 220bar - 50bar = 170bar used pressure):

$ kz calc rmv 15 170 16.2 55
17.70