Descent Time
-Total elapsed time from when the divers LEAVE the SURFACE to the time when they REACH the BOTTOM
Max rate of Descent
- 75 feet per minute max
- Round to next nearest whole minute (ex. 53 fsw = 43 seconds = 1 minute)
Bottom Time
(BT)
- Total elapsed time from when the divers LEAVE the SURFACE to the time they LEAVE the BOTTOM
- Round to the nearest whole minute
Total Decompression Time
(TDT)
-Total elapsed time from the time the diver LEAVES the BOTTOM to the time they ARRIVE on SURFACE
Max Ascent Rate
- 30 fpm
- 1 ft / 2 seconds
- Time needed to “off-gas”
Decompression Table
- Structured set of decompression schedules or limits
- Organized in order of increasing bottom times and depths
Decompression Schedules
- Specific decompression procedure for a combination of DEPTH and BOTTOM TIME
- Indicated as feet/minutes
Decompression Stop
- Specified depth a diver must remain at for a specified time
- Eliminates inert gasses from the body
- “Lets the fizz out”
Deepest Depth
-Deepest reading on depth gauge during a dive
Max Depth
- Deepest depth attained after correcting depth gauge for error
- Max depth is used on decompression table
Scuba Max Depth
- Max depth and deepest depth are the same
- Gauges in scuba are considered error free
Surface-Supplied Max Depth
- Surface Supplied uses “pnneumofathometer” not dive gauge
- max depth is = deepest reading on pneumo gauge + pneumo correction factor
- Gauges on surface supplied not considered error free
Unlimited / No decompression Limits
(No D)
-Max amount of time that can be spent at a given depth such that safe ascent can be made directly to surface with no stops
Types of Decompression Tables
1) Unlimited / No D Limits
- All scuba dives should be here
2) Residual Nitrogen Timetables
- Used for “repet” dives
- RNT
3) Air Decompression Table
Unlimited / No D Table
-Identifies that on dives in 20 fsw and shallower, unlimited bottom time can be achieved
Selection of Decompression Schedule
- Select schedule at the EXACT or NEXT LONGER bottom time of the dive
- Deviations from established decompression procedures are not permitted except in an emergency and with the guidance and recommendation of a Undersea Medical Officer (UMO) and with the CO’s or OIC’s approval
Should you use AIR or AIR/O2 option?
- All SCUBA dives are AIR dives
- Only Surface supplied dives can deliver 100% O2
- 100% O2 allows divers to off gas quicker due to lack of N2
Table and Schedule Format; For No D Dive
EX. 43 fsw, BT :40
T/S_45/:46, No D, F
Table and Schedule Format for Decompression Dive
EX. LS 0900, Depth 85’, BT :34
T/S_90/:35, AIR D, :04 STOP @ 20’, J
LS
Left Surface
RB
Reached Bottom
LB
Left Bottom
R
Reached Stop
L
Left a Stop
