Repetitive Dive
Surface Interval
Cold, Arduous Dive
Dive Computers
Safety Stop
Dive Tables
Decompression Theory
Residual Nitrogen
Bottom Time
No Decompression Limit
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Nitrogen Absorption
Outgas
Residual
N2
Final Level
N2
N2
Surface Interval
Dive 2
Dive 1
Additional
Absorbed
Absorbed
N2
Residual
N2
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N2
Revolving Charge Account
Purchase Table
0
100
200
Outstanding 300
Balance
400
500
600
700
800
900
100 200 300 400 500 600 700 800 900 1000
A B C D E F G H I
J
1
A
B
C
D
E
F
G
H
I
2
1
3
2
1
4
3
2
1
5
4
3
2
1
6
5
4
3
2
1
7
6
5
4
3
2
1
8
7
6
5
4
3
2
1
9
8
7
6
5
4
3
2
1
10
9
8
7
6
5
4
3
2
1
Credit Rating
Terms:
Limit - $1,000
$100 Increments
$100 Repay Inc
Repay Weekly
Repayment Table
New Credit Rating
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History of Decompression Sickness
(DCS)
• 1837 first described after hard hat salvage
operation (symptoms were attributed to cold
water)
• Caisson workers in the late 1800’s
• 1900 Haldane commissioned by British
Admirality to study and solve problem of DCS
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Development of Dive Tables
• Haldane conducted saturation experiments with
animals
• Established a 2:1 pressure ratio (half times)
• Four factors involved in N2 absorption
–
–
–
–
Pressure gradient
Tissues absorb at different rate
Blood flow is not equal to all parts of the body
Tissue half times
» 5 - 10 - 20 - 40 - 60
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DCS Risk factors
•
•
•
•
•
•
•
•
•
•
Deep dives
Repetitive dives
Multi-day diving
Fatigue
Dehydration
Age
Temperature
Exertion
Decompression diving
Rapid ascent
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Dive Tables
Dive Planning and
Scheduling Tool
• Depth
• Time
• Repetition
Types of Dives
No Stop Required
on Ascent
Mandatory
Stop on
Ascent
No Decompression
Repetitive
Decompression
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DCIEM Dive Tables Terminology
End of Dive
Repet Group
(RG) Letter
Repet Dive SI
10 min - 12 hrs
Surface Interval Time (SI)
( : )
Safety
Stop
15’-25’
Depth
Before Dive
Repet Factor (RF)
( : )
Safety
Stop
15’-25’
Safety
Stop
15’-25’
NDL
BT
Dive 1
Dive 2
ABT
Actual bottom time
ABT
Residual Nitrogen Time (RNT)
= No-D Limit(NDL)
- Residual No-D Limit (RNDL)
Dive 3
ABT
RNT = NDL - RNDL
EBT = ABT + RNT
Effective Bottom Time (EBT) = ABT + RNT
•EBT Must Be Less Than or Equal to RNDL
•The RG for each repetitive dive must be greater than that of the preceding dive
•After 3 days of repetitive diving, a day off is recommended
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Dedicated to the advancement and practice of scientific diving
Dive 1
87 Feet for 17 Minutes
Repetitive Group (RG) Letter
D
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Surface Interval (SI)
2:00
D
1.3
Repetitive Factor
(RF)
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Repetitive Dive
Planning
D
87’/17min
(SI)2:00
1.3
65 ft
Repetitive No-D Limit
RNDL = 21
Residual Nitrogen Time (RNT)
RNT = NDL - RNDL
= 35 - 21
= 14 min
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Repetitive Dive
D
87’/17min
(SI)2:00
1.3 E
65 ft
ABT = 19 min
Repetitive No-D Limit
RNDL = 21
Residual Nitrogen Time (RNT)
RNT = NDL - RNDL
= 35 - 21
= 14 min
Effective Bottom Time (EBT)
EBT = ABT + RNT
= 19 + 14
= 33 min Dedicated to the advancement and practice of scientific diving
Repetitive Factor
D
87’/17min
(SI)2:00
(SI) 3:00
1.3 E
1.3
65 ft
ABT = 19 min
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Repetitive Dive
Planning
D
87’/17min
(SI)2:00
(SI) 3:00
1.3 E
1.3
45 ft
65 ft
ABT = 19 min
Repetitive No-D Limit
RNDL = 50
Residual Nitrogen Time (RNT)
RNT = NDL - RNDL
= 75 - 50
= 25 min
Dedicated to the advancement and practice of scientific diving
Repetitive Dive
D
87’/17min
(SI)2:00
(SI) 3:00
1.3 E
1.3
G
45 ft
65 ft
ABT = 45 min
ABT = 19 min
Repetitive No-D Limit
RNDL = 50
Residual Nitrogen Time (RNT)
RNT = NDL - RNDL
= 75 - 50
= 25 min
Effective Bottom Time (EBT)
EBT = ABT + RNT
= 45 + 25
= 70 min Dedicated to the advancement and practice of scientific diving
Dive Computers
• The use of electronic dive computers to permit
multi-level diving is permissible, but only if such
instruments are used strictly according to the
manufacturer’s instructions and recommendations
and only for no-decompression diving.
• Computers should be monitored and the dive
controlled in a manner that will permit a direct
ascent to the surface at any time.
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Safe Dive Practices
Do not push tables/computer
to limits
Surface Intervals
1 hour minimum, longer is
better
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Safe Dive Practices
Slow Ascent Rates
Ascent rates shall be controlled at 30 fsw/min
from 60’ and not exceed 60 fsw/min from depth.
Reference:
Lang, M.A. and R.W. Hamilton (eds.). 1989. Proc. of the AAUS Dive
Computer Workshop. USC Catalina Marine Science Center. USC
Sea Grant Publ. USCSG-TR-01-89. 231 p.
Lang, M.A. and G.H. Egstrom (eds.). 1990. Proc. of the AAUS
Biomechanics of Safe Ascents Workshop. Woods Hole, MA.
American Academy of Underwater Sciences Publ. AAUSDSP-BSA01-90. 220p.
Dedicated to the advancement and practice of scientific diving
Safe Dive Practices
Safety Stops
A stop in the 10-30 fsw zone for 3-5 minutes is
required on every dive.
Reference:
Lang, M.A. and R.W. Hamilton (eds.). 1989. Proc. of the AAUS Dive
Computer Workshop. USC Catalina Marine Science Center. USC
Sea Grant Publ. USCSG-TR-01-89. 231 p.
Lang, M.A. and G.H. Egstrom (eds.). 1990. Proc. of the AAUS
Biomechanics of Safe Ascents Workshop. Woods Hole, MA.
American Academy of Underwater Sciences Publ. AAUSDSP-BSA01-90. 220p.
Dedicated to the advancement and practice of scientific diving
Flying after diving
Divers should have a minimum surface interval of 12
hours before ascending to altitude.
Dedicated to the advancement and practice of scientific diving
Summary
Safety
•
•
•
•
•
•
•
•
Don’t “Push” Tables
S.A.F.E. Dive
Safety Stops
Deepest Dive First
Multi-Day, Multi-Dives
Cold, Arduous Dive
Flying After Diving
High Altitude Diving
Emergency
Procedures
• NDL Inadvertently
Exceeded
• Cease Diving
• Observe for DCS
•If DCS Symptoms appear
• Administer 100% Oxygen
• Evacuate
Don’t Make The $30,000 Mistake
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