Easy Guide to Deco Computers

Recreational or Deco?

• Recreational limits say stay within no decompression time limit (NDL)

• You can go straight back to the surface unless you’re 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

24m dive NDL = 29 mins

24m dive NDL = 50 mins

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 OTU’s• 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

Vyper AIRHelO2

Vyper

What happens to dive computers when my NDL is exceeded?

RECREATIONAL AIR DIVE with deco

4 mins left for NO DECO

40 mins @ 24m followed by 11 mins @13m, then 3m until clear to surface

15L twinset

NO DECOMPRESSION DIVE

REACHED NO DECO LIMIT

0 usually flashesBeeps and backlight on

DECO

NO DEC TIME changes to ASC TIME

CEILING tells you where you SHOULD be now!!! to allow deco to count DOWN not UP!!

Ascent time means minimumtime before you can surface

Keep an eye on dive time and ASC time!

10 mins extra at 24 m causes 10 MORE mins of DECO

Some computers place an upward pointing arrow here

3m “ceiling”

“floor”

Not a problem if you’re carrying enough gas!!

Current depth

OK so we’ve taken 1 min to go up 11m and lost 1 min deco time

Off-gassing

floor

ceiling

DEEP STOP for 1 minute(optional)

11 mins at this depth but no loss in deco time? Why?

Well, you’re still on-gassing at the same time that you’re off-gassing !!

Usual stops can be 12m, 9m, 6m and 3m

Hourglass symbol appears when you are in the zone Ceiling

Floor

zone

Zone is above the floor and below the ceiling

Means that you are above the ceiling – DESCEND IMMEDIATELY

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 you’re in DECO again!!

NDL not reached yet

Max depthCurrent depth

NDL left

NO DECO TIME left

Dive time used

Currentdepth

110 secs STOP

13 secs of DEEPSTOP left

89 mins ASC TIME

48m ceiling.. a deco stop.In 13 secs next ceiling or decoappears

Current depth slightly deeper than ceiling

In the zone… hourglass

Now do you know yours?

• Remember.. If you’re 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

Deco Disadvantages

• Its boring

• Its cold

• Need lots of gas in reserve

• Double up on kit in case of failures

• Its cold!!

• Its boring!

Deco Advantages• You get the Rosalie Moller to yourself