Air Diving & Decompression

1
Air Diving Decompression
2
Sources

• Joiner, J.T. (ed.). 2001. NOAA Diving Manual -
  Diving for Science and Technology, Fourth
  Edition. Best Publishing Company, Flagstaff, AZ.
• Reference Materials
• In conjunction with this presentation, refer to
• NOAA Diving Manual Chapter 4
• NOAA Diving Manual Appendix IV
• NOAA Diving Manual Appendix III

3
Objectives

• After completing this training module you will be
  able to
• Differentiate between safe and reliable with
  regard to dive tables
• Differentiate between a single, repetitive and
  contingency decompression dive, and plan these
  dives using US Navy, and NOAA Dive Tables
• Explain the significance of Group Designation
  Letters

4
Objectives

• After completing this training module you will be
  able to
• Differentiate between safety stops and
  decompression stops
• List two options for dealing with omitted
  decompression
• List three advantages of using a dive computer
  rather than dive tables

5
Objectives

• After completing this training module you will be
  able to
• List three basic rules for diving a dive computer
• Differentiate between Dive Tables, Dive
  Computers, and PC Based Decompression Software

6
General

• Body tissues absorb additional nitrogen from air
  breathed during dives and release this excess
  nitrogen during ascent
• By keeping the amount of nitrogen absorbed and
  released within acceptable limits, the risk of
  decompression sickness is reduced

7
Decompression Table Development

• Physiologist J.S. Haldane developed a
  hypothetical model for nitrogen uptake and
  elimination around 1908
• Another notable in dive table development is
  Swiss cardiologist Prof. AA Buhlmann

8
Decompression Table Development

• ALL DIVE TABLES ARE HYPOTHETICAL
• All decompression modeling are based on theory
• Dive tables do not reflect the actual workings of
  the human body

9
Are Dive Tables Safe?

• Safe is not a good choice of words when
  discussing dive tables
• Virtually any hyperbaric exposure imposes an
  obligation for decompression
• Safe implies no risk of DCS - THERE IS ALWAYS A
  RISK OF DCS, even when diving well within table
  limits
• A better word to use when describing dive tables
  is Reliable

10
Acceptable Risk...

• Reliable dive tables are used to define
  acceptable risk
• Individual susceptibility to decompression
  disorders, environmental and other factors
  influence your risk of DCS
• You can do everything right and can still
  suffer a hit

11
Dive Planning Software

• The algorithms of Prof. A.A. Buhlmann are the
  fundamental basis for most dive planning software
  and many dive computers
• The different programs based on these algorithms
  manage the decompression models in slightly
  different ways

12
Decompression Planning

• Reliable decompression profiles have been
  produced using dive tables, dive computers, and
  dive planning software
• But again, no current method of calculating your
  decompression obligation can guarantee a zero
  risk of DCS

13
US Navy Dive Tables
14
Basics

• A single dive is any dive made more than 12 hours
  following a previous dive
• A repetitive dive is any dive made less than 12
  hours after surfacing from a prior dive

15
Basics

• US Navy Dive Table abbreviations / acronyms
• NDL (No Decompression Limit)
• ABT (Actual Bottom Time)
• SIT (Surface Interval Time)
• RNT (Residual Nitrogen Time)
• ESDT (Equivalent Single Dive Time)

16
US Navy Dive Table 3
17
Basics

• Depth Range USN Dive Tables give depth in feet
  and meters

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18
Basics

• No-Decompression Limit (NDL) The theoretical
  amount of time a diver can remain at a given
  depth and return directly to the surface

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19
Basics

• Dive Time is given in minutes
• Actual Bottom Time (ABT) starts when the diver
  leaves the surface and ends when the diver begins
  a direct, uninterrupted ascent to the surface at
  a rate of no more than 30 feet per minute

20
Basics

• Group Designation Letter A representation of the
  amount of nitrogen a diver absorbs during a dive
  to a given depth for a given period of time

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21
Basics

• Depth or Time that do not equal an increment
  available on the dive tables is to be rounded up
• For example A dive with an actual depth and time
  of 51 feet for 21 minutes would be computed as 60
  feet for 25 minutes

22
No-Decompression Limits

• The NDL for a dive from 61 to 70 feet is 50
  minutes

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23
Repetitive Dives

• A repetitive dive is any dive made less than 12
  hours after surfacing from a prior dive
• To compute a repetitive dive schedule, you must
  determine the Group Designation Letter and take
  into account the Residual Nitrogen from the
  previous dive(s)

24
Repetitive Dives

• Use this simple format as a worksheet for
  computing repetitive dive profiles

Surface Interval Time (SIT)
Group Letter
Group Letter
Group Letter
Depth
Depth
ABT
Residual Nitrogen Time (RNT) ABT ESDT
25
Determine a Group Designation

• A dive to 80 feet for 20 minutes produces a Group
  Designation of E

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26
Determine a Group Designation

• A dive to 80 feet for 20 minutes produces a Group
  Designation of E

E
80 ft
20 min
27
USN Table 4
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28
USN Table 4

• Table 4 is a combination of two tables
• The upper portion is Surface Interval Time (SIT)
• The time ranges are in hours and minutes
• The lower portion provides Residual Nitrogen Time
• RNT is necessary to properly compute a repetitive
  dive

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29
New Group Designation

• 80 ft/20 min produces a Letter Group of E
• After a 200 SIT the New Group Designation is C

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30
New Group Designation

• 80 ft/20 min produces a Letter Group of E
• After a 200 SIT the New Group Designation is C

200
E
C
80 ft
20 min
31
Repetitive Dive

• As a C diver, you want to plan a no-stop
  repetitive dive back to 80 ft for 20 minutes
• To determine the Residual Nitrogen from the first
  dive use the lower portion of USN Table 4
• You will also need to know the NDL for 80 ft
  (Refer to the No-decompression Limit column of
  Table 3)

32
Determine the RNT

• Trace down the column below C and across from 80
  ft. Where these points intersect is the RNT to be
  used to compute the next dive.

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33
Determine the Adjusted NDL

• The NDL for 80 ft is 40 minutes
• Since this is a Repetitive Dive you must adjust
  for the RNT and determine the Adjusted NDL
• NDL RNT Adjusted NDL

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34
Determine the Adjusted NDL
NDL 40 -RNT -13
Adjusted NDL 27

• The Adjusted NDL gives you the maximum bottom
  time for a return to 80 ft as a C diver, without
  incurring required decompression

35
Repetitive Dive

• You now know a repetitive dive to 80 ft for 20
  minutes can be conducted within the
  No-Decompression Limits of the Navy Dive Tables
• To complete the Repetitive Dive planning process,
  determine the Equivalent Single Dive Time (ESDT)

36
Equivalent Single Dive Time

• The RNT for a C diver to return to 80 ft is 13
  minutes
• The Actual Bottom Time (ABT) planned is 20 minutes

RNT 13 ABT 20
ESDT 33
37
Determine a Final Letter Group

• Take the ESDT back to Table 3 to determine the
  Group Designation Letter at the end of the
  repetitive dive

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38
Repetitive Dive Profile
200 (SIT)
E
C
H
80 ft
80 ft
20 min
RNT 13 min ABT 20 min ESDT 33 min
39
Exceptions to Normal Repetitive Dive Planning

• Computing a dive to 60 ft for 30 minutes with a
  30 minute SIT followed a dive to 60 ft indicates
  an RNT of 36
• How can this be? The NDL for 60 ft is 60 minutes.
  The diver should have 30 minutes of unused NDL
  prior to the SIT
• This seems to show the diver on-gassing nitrogen
  during the surface interval

40
Exceptions to Normal Repetitive Dive Planning

• This is an exception to the tables
• The diver can be conservative and use the
  indicated RNT to compute the dive profile
• OR The diver can ignore the indicated RNT and
  use the remaining NDL from dive one to compute
  the dive profile

41
Surface Intervals Less Than Ten Minutes

• Table 4 does not allow for a SIT of less than ten
  minutes
• Dives with a surface interval of less than ten
  minutes are considered ONE DIVE
• Add the bottom times together and use the deepest
  depth reached to calculate the dive profile

42
Decompression

• Technically, decompression is something that
  happens on every dive
• However, for the purposes of this discussion
  decompression means the diver is required to
  follow a specific time, depth, and breathing gas
  profile

43
Decompression

• A decompression profile, or table, is designed to
  allow the diver to ascend to the surface without
  DCS symptoms
• A decompression profile may involve stops, or
  only require a specific ascent rate without stops

44
Precautionary Decompression Stops

• Commonly know as safety stops
• While not required by US Navy Dive Tables, safety
  stops are recommended for all no-stop dives
  conducted 60 fsw or deeper, plus all repetitive
  dives
• Safety stops should be performed for three to
  five minutes in the 10 to 20 fsw depth range

45
Decompression Dives

• Unlike a safety stop, a mandatory decompression
  stop is required by the dive tables
• Decompression dives have substantially greater
  logistical requirements, and are generally
  believed to increase the risk DCS

46
Decompression Dives

• For the purpose of this presentation
  decompression dive calculation is presented for
  contingency planning purposes only
• Additional training is necessary prior to
  engaging in dives involving required or mandatory
  decompression stops

47
US Navy Table 5
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See No-Decompression Table 3 for Repetitive
Groups Repetitive Dives may not follow
Exceptional Exposure Dives
48
US Navy Table 5

• A dive to 60 ft for 65 minutes results in a
  required decompression stop at 10 ft for 2
  minutes and a Repetitive Group of K

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49
Decompression Profile

• A dive to 60 ft for 65 minutes results in a
  required decompression stop at 10 ft for 2
  minutes and a Repetitive Group of K

K
10 ft
2 min
60 ft
65 min
50
Omitted Decompression 1

• A diver realizes he has exceeded his planned dive
  schedule and does not have contingency tables
• He should ascend at a proper rate and stop at 10
  to 15 fsw for a minimum of 15 minutes or until
  cylinder pressure reaches 300 psi, whichever
  comes first

51
Omitted Decompression 1

• Consult USN Decompression tables upon surfacing
• If the time spent at 10 to 15 feet did not equal
  or exceed the required time, the diver should be
  placed on oxygen for a minimum of 30 minutes,
  observed and restricted from diving for 12 hours

52
Omitted Decompression 2

• A diver does not have sufficient breathing gas to
  complete his required decompression and is forced
  to surface
• If asymptomatic, and he can safely return to the
  water within five minutes, he and a buddy should
  return to the depth of the missed decompression
  and remain for 1 ½ times the required stop time

53
Omitted Decompression 2

• If he cannot be returned to the water within five
  minutes, he should be placed on oxygen for a
  minimum of 60 minutes
• If asymptomatic after breathing oxygen for 60
  minutes, the diver should observed for signs and
  symptoms of DCS and be restricted from diving for
  a minimum of 12 hours

54
USN Dive Table Altitude Assumptions

• The altitude at the surface of the water in which
  a dive is made is no more than 1,000 feet above
  sea level
• For at least 12 hours following any dive, the
  divers will remain at an altitude no higher than
  1,000 feet above sea level

55
Reverse Profile Dives

• A reverse profile can refer to a series of
  repetitive dives during which the deepest dive is
  not the first in the series, or to a single
  multi-level dive during which the diver goes
  deeper after completing a shallower phase

56
Reverse Profile Dives

• There is no convincing evidence that reverse
  profile dives within the no-decompression limits
  subject a diver to an increased risk of DCS
• Reverse Profile Dives should be conducted in
  water depths less than 130 fsw, within
  no-decompression limits, and with depth
  differentials of less than 40 fsw

57
Cold and Arduous Dives

• Compute the dive profile for a dive that is cold
  or arduous by using the next greater time
  increment appearing on the tables
• For example a dive with an ABT of 40 minutes
  should be computed using a dive time of 45
  minutes, to compensate for cold or arduous
  conditions

58
NOAA Air Dive Tables
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59
NOAA Air Dive Tables

• NOAA Air Dive tables are based on US Navy Tables
• They combine portions of US Navy Tables 3, 4, and
  5
• The maximum depth available using NOAA Dive
  Tables is 130 fsw
• To assist with dive profile calculation, the NOAA
  Tables also provide Adjusted Maximum Dive Times
  as part of Chart 3

60
NOAA Air Dive Tables

• Information flows clockwise from Chart 1, to
  Chart 2, to Chart 3

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61
NOAA Dive Table Chart 1

• As with USN Dive Tables, find the depth range
  along the left of Chart 1
• Trace across the row to the time increment
  required
• Trace down the column to find the Group Letter

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62
NOAA Dive Table Chart 1

• Note that Maximum No-Stop Time Limits for each
  depth increment is indicated by a circle around
  the maximum allowable time

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63
NOAA Dive Table Chart 1

• Blocks to the right of the NDL indicate Required
  Decompression
• The Red number is the time requiring
  Decompression
• The White number in the black is the stop time
  required at 10 fsw

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64
NOAA Dive Table Chart 2

• Chart 2 is Surface Interval Time
• This is the same as USN Tables
• Flow in from the top and exit the chart to the
  left to find the new letter group

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65
NOAA Dive Table Chart 3

• Chart 3 provides Residual Nitrogen Time (Top
  numbers, in Red) and Adjusted Maximum Dive Time
  (bottom numbers, in black)
• Enter the chart from the right, exit through the
  top

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66
ESDT Formula

• Just like with USN Tables, to properly compute
  repetitive dives you will need to determine your
  Equivalent Single Dive Time (ESDT)

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67
Practice Problems

• Refer to the US Navy Dive Tables (Appendix IV of
  the NOAA Diving Manual) to answer the following
  practice problems

68
Practice Problem 1

• You wish to make a dive to 56 fsw for 25 minutes,
  what will your group letter be at the end of the
  dive?

69
Answer 1

• You wish to make a dive to 56 fsw for 25 minutes,
  what will your group letter be at the end of the
  dive?

E
56 ft
25 min
70
Practice Problem 2

• As an E diver, you take a 100 surface interval,
  what is your new group designation?

71
Answer 2

• As an E diver, you take a 100 surface interval,
  what is your new group designation?
• D
• Use USN Table 4, find E, trace across the row to
  the SIT range that includes 100, trace down the
  column to find the new group designation

72
Practice Problem 3

• A dive team makes a dive to 80 fsw for 10 minutes
  followed by a 200 SIT, what is their RNT for a
  dive to 60 fsw?

73
Answer 3

• A dive team makes a dive to 80 fsw for 10 minutes
  followed by a 200 SIT, what is their RNT for a
  dive to 60 fsw?
• 11 minutes
• Computing the dive and SIT results in a Group
  Letter of B
• Trace down the B column of Table 4 and across the
  row for 60 fsw. Where these points meet is the RNT

74
Practice Problem 4

• A B diver wants to dive to 60 fsw, what is her
  Adjusted No-Decompression Limit?

75
Answer 4

• A B diver wants to dive to 60 fsw, what is her
  Adjusted No-Decompression Limit?
• 49 minutes
• Determine the RNT for a B diver returning to 60
  ft. Look up the NDL for 60 ft
• NDL RNT Adjusted NDL

76
Practice Problem 5

• A C diver wants to dive to 90 fsw for 15
  minutes, what is his ESDT?

77
Answer 5

• A C diver wants to dive to 90 fsw for 15
  minutes, what is his ESDT?
• 26 minutes
• RNT ABT ESDT

78
Practice Problem 6

• A dive team has made a dive to 55 ft for 30
  minutes. Without entering required decompression,
  how long a SIT must the team take before they may
  return to 55 ft for 40 minutes?

55 ft
55 ft
30 min
40 min
79
Answer 6

• A dive team has made a dive to 55 ft for 30
  minutes. Without entering required decompression,
  how long a SIT must the team take before they may
  return to 55 ft for 40 minutes?

229 357
J
C
F
55 ft
55 ft
RNT 17 min
30 min
40 min
57 min
80
Practice Problem 7

• After your surface interval your Letter Group is
  D. What is the deepest you could dive for 30
  minutes and not enter required decompression?

81
Answer 7

• After your surface interval your Letter Group is
  D. What is the deepest you could dive for 30
  minutes and not enter required decompression?
• 70 fsw
• NDL RNT Adjusted NDL
• 30 RNT ESDT

82
Practice Problem 8

• You have an RNT of 76 minutes for a repetitive
  dive to 50 ft. What was your Group Designation
  Letter at the end of your SIT?

83
Answer 8

• You have an RNT of 76 minutes for a repetitive
  dive to 50 ft. What was your Group Designation
  Letter at the end of your SIT?
• I
• Using Table 4 find 50 ft, trace along the 50 ft
  row until you locate the RNT, trace up to
  identify the Group Designation.

84
Practice Problem 9

• You have an NDL of 20 minutes. To what depth
  would you be diving? This is not a repetitive
  dive.

85
Answer 9

• You have an NDL of 20 minutes. To what depth
  would you be diving? This is not a repetitive
  dive.
• 110 fsw
• Using Table 3, trace down the NDL column until
  you locate the desired NDL, trace left to find
  the depth.

86
Practice Problem 10

• You make a dive to 40 fsw for 205 minutes, what
  is your dive profile and repetitive group?

87
Answer 10

• You make a dive to 40 fsw for 205 minutes, what
  is your dive profile and repetitive group?
• Use USN Table 5, round 205 up to 210, trace the
  210 row to the right to determine the profile.

N
10 ft
2 min
40 ft
205 min
88
Practice Problem 11

• You have a required decompression stop for 1
  minute at 20 ft and 69 minutes at 10 ft. How long
  was the dive and to what depth?

89
Answer 11

• You have a required decompression stop for 1
  minute at 20 ft and 69 minutes at 10 ft. How long
  was the dive and to what depth?
• 200 minutes at 60 fsw
• Using Table 5, trace down the 20 ft and 10 ft
  Decompression Stop column until you find the
  required stop times, trace left to find the
  bottom time and depth.

90
Dive Computers
91
Dive Computers

• Dive computers are electronic devices that
  monitor the divers depth and time and give a
  running calculation of the divers decompression
  status
• Dive computers are based on mathematical models
  which attempt to describe the absorption and
  elimination of nitrogen within the human body

92
Dive Computers

• Unlike Dive Tables, Dive Computers
• Compute a dive profile in real time
• Compute multilevel dives
• Have automatic dive log functions
• Some dive computers can provide information on
  gas consumption, and/or be used with breathing
  gases other than air

93
Dive Computers

• To dive a dive computer
• Each member of the dive team must have their own
  unit
• On any given dive, the most conservative unit
  controls the dive i.e., call the dive on the
  most conservative information
• It is the divers responsibility to understand
  the information being displayed by the computer
  and to adhere to the units operational
  requirements

94
PC Based Decompression Software

• There are a variety of PC based decompression
  software currently available
• This software allows a diver to cut custom dive
  tables
• These programs are another way of managing your
  decompression obligation
• They are not necessarily better than another
  method, but an additional tool for consideration

95
A Note On Decompression Software

• Many PC based decompression software programs and
  some dive computers allow the user to customize
  settings such as gradient factors, gas
  percentages, conservatism, etc.

96
A Note On Decompression Software

• Modification of these settings can produce widely
  varying dive schedules for a given dive, and may
  produce an overly aggressive decompression
  profile for a given diver, increasing the risk of
  DCS

97
A Note On Decompression Software

• Research and understand the features and
  functions of the decompression profiling method
  you plan to use, use it as designed, and remember
  decompression schedules are tools for managing
  risk, not eliminating it

98
Study Questions

• Use the following study questions to review some
  of the information presented in this self study
  module. When you are finished you can print out
  your study questions results.

99
Self Study Questions

• What is the best choice of words when discussing
  dive tables and why?
• Safe because dive tables are based on proven
  physiological models reflecting how the human
  body absorbs and eliminates nitrogen.
• Reliable because even though all dive tables are
  based on hypothetical decompression models,
  reliable tables provide acceptable risk.
• Best guess because there is no theoretical basis
  for dive tables.
• Individually specific because modern
  decompression models allow the user to account
  for all of the factors influencing decompression
  risk.

100
Self Study Questions

• What is the best choice of words when discussing
  dive tables and why?
• Safe because dive tables are based on proven
  physiological models reflecting how the human
  body absorbs and eliminates nitrogen.
• Reliable because even though all dive tables are
  based on hypothetical decompression models,
  reliable tables provide acceptable risk.
• Best guess because there is no theoretical basis
  for dive tables.
• Individually specific because modern
  decompression models allow the user to account
  for all of the factors influencing decompression
  risk.

101
Self Study Questions

• US Navy and NOAA Dive Tables define a single dive
  as
• any dive made more than 12 hours following a
  previous dive.
• any dive made less than 12 hours after surfacing
  from a prior dive.
• any dive made more than 24 hours following a
  previous dive.
• any dive made less than 24 hours after surfacing
  from a prior dive.

102
Self Study Questions

• US Navy and NOAA Dive Tables define a single dive
  as
• any dive made more than 12 hours following a
  previous dive.
• any dive made less than 12 hours after surfacing
  from a prior dive.
• any dive made more than 24 hours following a
  previous dive.
• any dive made less than 24 hours after surfacing
  from a prior dive.

103
Self Study Questions

• Us Navy and NOAA Dive Tables define a _____ dive
  as any dive made less than 12 hours after
  surfacing from a prior dive.
• single
• repetitive
• decompression
• contingency

104
Self Study Questions

• Us Navy and NOAA Dive Tables define a _____ dive
  as any dive made less than 12 hours after
  surfacing from a prior dive.
• single
• repetitive
• decompression
• contingency

105
Self Study Questions

• Even though this presentation does not address
  required decompression dive procedures in detail,
  divers using US Navy or NOAA Dive Tables are
  expected to know how to calculate required
  decompression schedules for contingency planning
  purposes.
• True
• False

106
Self Study Questions

• Even though this presentation does not address
  required decompression dive procedures in detail,
  divers using US Navy or NOAA Dive Tables are
  expected to know how to calculate required
  decompression schedules for contingency planning
  purposes.
• True
• False

107
Self Study Questions

• What is the significance of a Group Designation
  Letter with US Navy or NOAA Dive Tables?
• It represents the amount of nitrogen a diver
  absorbs during a dive to a given depth for a
  given period of time.
• It represents the amount of nitrogen a diver
  off-gases during a dive.
• It represents the no-decompression limit for a
  given depth for a given period of time.
• It represents the amount of nitrogen a diver
  absorbs during a no-decompression dive. Once a
  diver reaches the no-decompression limit the
  diver becomes saturated with nitrogen and Group
  Designation Letters are no longer used.

108
Self Study Questions

• What is the significance of a Group Designation
  Letter with US Navy or NOAA Dive Tables?
• It represents the amount of nitrogen a diver
  absorbs during a dive to a given depth for a
  given period of time.
• It represents the amount of nitrogen a diver
  off-gases during a dive.
• It represents the no-decompression limit for a
  given depth for a given period of time.
• It represents the amount of nitrogen a diver
  absorbs during a no-decompression dive. Once a
  diver reaches the no-decompression limit the
  diver becomes saturated with nitrogen and Group
  Designation Letters are no longer used.

109
Self Study Questions

• Using US Navy or NOAA Air Dive Tables, a dive to
  70 feet (22m) for 31 minutes results in a Group
  Designation Letter of
• F
• G
• H
• I

110
Self Study Questions

• Using US Navy or NOAA Air Dive Tables, a dive to
  70 feet (22m) for 31 minutes results in a Group
  Designation Letter of
• F
• G
• H
• I

111
Self Study Questions

• Using US Navy or NOAA Air Dive Tables, a dive to
  71 feet for 15 minutes followed by a one hour
  surface interval will result in a Group
  Designation Letter of
• B
• C
• D
• E

112
Self Study Questions

• Using US Navy or NOAA Air Dive Tables, a dive to
  71 feet for 15 minutes followed by a one hour
  surface interval will result in a Group
  Designation Letter of
• B
• C
• D
• E

113
Self Study Questions

• Using US Navy or NOAA Air Dive Tables, a dive to
  55 feet for 40 minutes followed by a 90 minute
  surface interval and a repetitive dive to 63 feet
  for 20 minutes will result in a Group Designation
  Letter of
• G
• H
• J
• K

114
Self Study Questions

• Using US Navy or NOAA Air Dive Tables, a dive to
  55 feet for 40 minutes followed by a 90 minute
  surface interval and a repetitive dive to 63 feet
  for 20 minutes will result in a Group Designation
  Letter of
• G
• H
• J
• K

115
Self Study Questions

• A diver using US Navy or NOAA Air Dive Tables
  plans a dive to 100' for 25 minutes. The diver
  should calculate contingency dive plans
  accounting for exceeding both depth and time.
  Exceeding the planned depth by as little as a
  foot results in a five plan of
• 110' for 25 minutes, requires a decompression
  stop at 10' for 3 minutes.
• 100' for 40 minutes, requires a decompression
  stop at 15' for 10 minutes.
• 110' for 30 minutes, requires a decompression
  stop at 10' for 7 minutes.
• 100' for 25 minutes requires no decompression
  stop.

116
Self Study Questions

• A diver using US Navy or NOAA Air Dive Tables
  plans a dive to 100' for 25 minutes. The diver
  should calculate contingency dive plans
  accounting for exceeding both depth and time.
  Exceeding the planned depth by as little as a
  foot results in a five plan of
• 110' for 25 minutes, requires a decompression
  stop at 10' for 3 minutes.
• 100' for 40 minutes, requires a decompression
  stop at 15' for 10 minutes.
• 110' for 30 minutes, requires a decompression
  stop at 10' for 7 minutes.
• 100' for 25 minutes requires no decompression
  stop.

117
Self Study Questions

• Using US Navy or NOAA Air Dive Tables, determine
  the residual nitrogen time (RNT) for a diver with
  a Group Designation Letter of G wanting to make a
  repetitive five to 60'.
• 16
• 56
• 37
• 44

118
Self Study Questions

• Using US Navy or NOAA Air Dive Tables, determine
  the residual nitrogen time (RNT) for a diver with
  a Group Designation Letter of G wanting to make a
  repetitive five to 60'.
• 16
• 56
• 37
• 44

119
Self Study Questions

• Using US Navy or NOAA Air Dive Tables determine
  the adjusted maximum dive time for a repetitive
  dive with no decompression for a diver with a
  Group Designation Letter of D wanting to make a
  repetitive dive to 50'.
• 29
• 79
• 17
• 43

120
Self Study Questions

• Using US Navy or NOAA Air Dive Tables determine
  the adjusted maximum dive time for a repetitive
  dive with no decompression for a diver with a
  Group Designation Letter of D wanting to make a
  repetitive dive to 50'.
• 29
• 79
• 17
• 43

121
Self Study Questions

• ______ stops are recommended while ______ stops
  are required by the dive tables.
• Decompression / safety
• Safety / omitted
• Safety / decompression
• Precautionary / scheduled

122
Self Study Questions

• ______ stops are recommended while ______ stops
  are required by the dive tables.
• Decompression / safety
• Safety / omitted
• Safety / decompression
• Precautionary / scheduled

123
Self Study Questions

• A diver realizes he has exceeded his planned dive
  schedule and does not have contingency tables.
  The diver can
• Ascend at a proper rate and stop at 10 to 15 fsw
  for a minimum of 15 minutes or until cylinder
  pressure reaches 300 psi. If the time spent at 10
  to 15 ' did not equal or exceed the required
  decompression time, the diver should be placed on
  oxygen for a minimum of 30 minutes, observed, and
  restricted from diving for 12 hours.
• Surface and, if asymptomatic, return to the water
  within five minutes to the depth of the missed
  decompression and remain for one and one-half
  times the required stop time.
• Surface and breath oxygen for a minimum of 60
  minutes.
• All of the above.
• None of the above.

124
Self Study Questions

• A diver realizes he has exceeded his planned dive
  schedule and does not have contingency tables.
  The diver can
• Ascend at a proper rate and stop at 10 to 15 fsw
  for a minimum of 15 minutes or until cylinder
  pressure reaches 300 psi. If the time spent at 10
  to 15 ' did not equal or exceed the required
  decompression time, the diver should be placed on
  oxygen for a minimum of 30 minutes, observed, and
  restricted from diving for 12 hours.
• Surface and, if asymptomatic, return to the water
  within five minutes to the depth of the missed
  decompression and remain for one and one-half
  times the required stop time.
• Surface and breath oxygen for a minimum of 60
  minutes.
• All of the above.
• None of the above.

125
Self Study Questions

• Unlike Dive Tables, Dive Computers calculate a
  dive profile in "real time" compute "multilevel
  dives" and have automatic dive log functions.
• True
• False

126
Self Study Questions

• Unlike Dive Tables, Dive Computers calculate a
  dive profile in "real time" compute "multilevel
  dives" and have automatic dive log functions.
• True
• False

127
Self Study Questions

• Unlike Dive Tables, Dive Computers and PC Based
  Decompression Software offer a method of
  calculating decompression obligation with zero
  risk of DCS.
• True
• False

128
Self Study Questions

• Unlike Dive Tables, Dive Computers and PC Based
  Decompression Software offer a method of
  calculating decompression obligation with zero
  risk of DCS.
• True
• False