Easy Guide to Deco Computers

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Easy Guide to Deco Computers
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Recreational or Deco?

• Recreational limits say stay within no
  decompression time limit (NDL)
• You can go straight back to the surface unless
  youre within 3 pressure groups of the NDL (grey
  areas of RDP) or below 30m
• The safety stop is just that!
• 24m dive on Air NDL 29 mins
• 24m dive on EANx32 NDL 50 mins

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24m dive NDL 29 mins
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24m dive NDL 50 mins
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What happens if I stay beyond NDL?

• You NEED to do COMPULSORY stops
• You can no longer go straight to the surface
• You have nitrogen bubble build up
• You need to monitor OTUs
• You NEED a DECO plan
• You need to know what depths to stop at and for
  how long
• You NEED to know what those flashy computers
  actually mean
• YOU NEED ENOUGH GAS

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What happens to dive computers when my NDL is
exceeded?
Vyper AIR
Vyper
HelO2
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40 mins _at_ 24m followed by 11 mins _at_13m, then 3m
until clear to surface
RECREATIONAL AIR DIVE with deco
15L twinset
4 mins left for NO DECO
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NO DECOMPRESSION DIVE
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REACHED NO DECO LIMIT
0 usually flashes Beeps and backlight on
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DECO
CEILING tells you where you SHOULD be now!!! to
allow deco to count DOWN not UP!!
NO DEC TIME changes to ASC TIME
Ascent time means minimum time before you can
surface
Keep an eye on dive time and ASC time!
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Some computers place an upward pointing arrow here
3m ceiling
floor
10 mins extra at 24 m causes 10 MORE mins of DECO
Not a problem if youre carrying enough gas!!
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Current depth
ceiling
floor
OK so weve taken 1 min to go up 11m and lost 1
min deco time
Off-gassing
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DEEP STOP for 1 minute (optional)
11 mins at this depth but no loss in deco time?
Why?
Well, youre still on-gassing at the same time
that youre off-gassing !!
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Hourglass symbol appears when you are in the zone
Ceiling
zone
Floor
Zone is above the floor and below the ceiling
Usual stops can be 12m, 9m, 6m and 3m
Means that you are above the ceiling DESCEND
IMMEDIATELY
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NOW A NO DECOMPRESSION DIVE AGAIN
Some conservative computers add on a normal
safety stop at this point
This will only stay NDL if you do not go below
this 3m floor, otherwise youre in DECO again!!
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NDL not reached yet
Max depth
Current depth
NDL left
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Current depth
NO DECO TIME left
110 secs STOP
Dive time used
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Current depth slightly deeper than ceiling
89 mins ASC TIME
13 secs of DEEPSTOP left
48m ceiling .. a deco stop. In 13 secs next
ceiling or deco appears
In the zone hourglass
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Now do you know yours?

• Remember.. If youre going into deco, make sure
  that you have ample gas
• Split your main gas into thirds
• One third in
• One third out and
• One third remains for that emergency
• Deco gas is split in half
• Half used, half kept in reserve

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Deco Disadvantages

• Its boring
• Its cold
• Need lots of gas in reserve
• Double up on kit in case of failures
• Its cold!!
• Its boring!

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Deco Advantages

• You get the Rosalie Moller to yourself