1. Easy Guide to Deco Computers

2. 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

3. 24m dive NDL = 29 mins

4. 24m dive NDL = 50 mins

6. 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

7. What happens to dive computers when my NDL is exceeded?
Vyper
Vyper AIR
HelO2

8. RECREATIONAL AIR DIVE with deco
40 24m followed by 11 then 3m until clear to surface
RECREATIONAL AIR DIVE with deco
4 mins left for NO DECO
15L twinset

9. NO DECOMPRESSION DIVE

10. REACHED NO DECO LIMIT
0 usually flashes
Beeps and backlight on

11. CEILING tells you where you SHOULD be now!!!
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!

12. 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 you’re carrying enough gas!!

13. Current depth
ceiling
floor
OK so we’ve taken 1 min to go up 11m and lost 1 min deco time
Off-gassing

14. 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 !!

15. 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

18. 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!!

19. NDL not reached yet
Max depth
Current depth
NDL left

20. Current
depth
NO DECO
TIME left
110 secs
STOP
Dive time used

21. Current depth
slightly deeper
than ceiling
89 mins ASC TIME
48m ceiling
.. a deco stop.
In 13 secs next
ceiling or deco
appears
13 secs of DEEPSTOP
left
In the zone
… hourglass

22. 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

23. Deco Disadvantages Its boring Its cold Need lots of gas in reserve
Double up on kit in case of failures
Its cold!!
Its boring!

24. Deco Advantages
You get the Rosalie Moller to yourself