Air Diving & Decompression
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
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
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
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
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
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
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
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”
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”
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
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
US Navy Dive Tables
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
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)
US Navy Dive Table 3
• Depth Range: USN Dive
Tables give depth in feet
and meters
Credit: Permission granted by Best Publishing Company (NOAA Diving
Manual 4th Ed.) Flagstaff, AZ
Basics
• No-Decompression
Limit: (NDL) The
theoretical amount of
time a diver can
remain at a given
depth and return
directly to the surface
Credit: Permission granted by Best Publishing Company (NOAA
Diving Manual 4th Ed.) Flagstaff, AZ
Basics
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
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
Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ
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
• The NDL for a dive
from 61 to 70 feet is 50
minutes
Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ
No-Decompression Limits
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)
Repetitive Dives
• Use this simple format as a worksheet for
computing repetitive dive profiles
Group
Letter
Depth
Surface
Interval
Time (SIT)
Group
Letter
Group
Letter
Depth
ABT
Residual Nitrogen
Time (RNT)
+ ABT
ESDT
Determine a Group
Designation
• A dive to 80 feet for 20 minutes produces a
Group Designation of E
Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ
Determine a Group
Designation
• A dive to 80 feet for 20 minutes produces a
Group Designation of E
E
80 ft
20 min
USN Table 4
Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ
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
Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ
• 80 ft/20 min
produces a Letter
Group of E
• After a 2:00 SIT
the New Group
Designation is C
Credit: Permission granted by Best Publishing Company (NOAA Diving
Manual 4th Ed.) Flagstaff, AZ
New Group Designation
New Group Designation
•80 ft/20 min produces a Letter Group of E
•After a 2:00 SIT the New Group Designation is C
2:00
E
80 ft
20 min
C
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)
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.
Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ
• 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
Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ
Determine the Adjusted NDL
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
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)
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
+ ABT
ESDT
13
+ 20
33
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
Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ
Repetitive Dive Profile
2:00 (SIT)
E
80 ft
C
H
80 ft
20 min
RNT 13 min
+ ABT 20 min
ESDT 33 min
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
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
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
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
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
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
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
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
Credit: Permission granted by Best Publishing Company (NOAA Diving Manual
4th Ed.) Flagstaff, AZ
US Navy Table 5
* See No-Decompression Table 3 for Repetitive Groups
** Repetitive Dives may not follow Exceptional Exposure Dives
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
Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ
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
60 ft
65 min
2 min
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
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
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
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
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
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
Reverse Profile Dives
• There is no convincing evidence that
reverse profile dives within the nodecompression 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
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
Credit: Permission granted by Best Publishing Company (NOAA Diving
Manual 4th Ed.) Flagstaff, AZ
NOAA Air Dive Tables
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
• Information flows
clockwise from
Chart 1, to Chart 2,
to Chart 3
Credit: Permission granted by Best Publishing Company (NOAA
Diving Manual 4th Ed.) Flagstaff, AZ
NOAA Air Dive Tables
• 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
Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ
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
Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ
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
Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ
NOAA Dive Table – Chart 1
• 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
Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ
NOAA Dive Table – Chart 2
• 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
Credit: Permission granted by Best Publishing Company (NOAA
Diving Manual 4th Ed.) Flagstaff, AZ
NOAA Dive Table – Chart 3
• Just like with USN
Tables, to properly
compute repetitive
dives you will need
to determine your
Equivalent Single
Dive Time (ESDT)
Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ
ESDT Formula
Practice Problems
• Refer to the US Navy Dive Tables
(Appendix IV of the NOAA Diving
Manual) to answer the following practice
problems
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?
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
Practice Problem 2
• As an E diver, you take a 1:00 surface
interval, what is your new group
designation?
Answer 2
• As an E diver, you take a 1:00 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 1:00,
trace down the column to find the new
group designation
Practice Problem 3
• A dive team makes a dive to 80 fsw for 10
minutes followed by a 2:00 SIT, what is
their RNT for a dive to 60 fsw?
Answer 3
• A dive team makes a dive to 80 fsw for 10
minutes followed by a 2:00 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
Practice Problem 4
• A “B” diver wants to dive to 60 fsw, what
is her Adjusted No-Decompression Limit?
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
Practice Problem 5
• A ‘C’ diver wants to dive to 90 fsw for 15
minutes, what is his ESDT?
Answer 5
• A ‘C’ diver wants to dive to 90 fsw for 15
minutes, what is his ESDT?
• 26 minutes
• RNT + ABT = ESDT
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
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?
F
55 ft
2:29
3:57
C
J
55 ft
30 min
RNT 17 min
+ 40 min
57 min
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?
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
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?
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.
Practice Problem 9
• You have an NDL of 20 minutes. To what
depth would you be diving? This is not a
repetitive dive.
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.
Practice Problem 10
• You make a dive to 40 fsw for 205
minutes, what is your dive profile and
repetitive group?
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
40 ft
205 min
2 min
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?
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.
Dive Computers
Dive Computers
• Dive computers are electronic devices that
monitor the diver’s depth and time and
give a running calculation of the diver’s
decompression status
• Dive computers are based on
mathematical models which attempt to
describe the absorption and elimination of
nitrogen within the human body
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
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 diver’s responsibility to understand
the information being displayed by the
computer and to adhere to the unit’s
operational requirements
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
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.
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
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
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.
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.
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.
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.
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.
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
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
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.
a. True
b. False
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.
a. True
b. False
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 nodecompression limit the diver becomes saturated with
nitrogen and Group Designation Letters are no longer used.
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 nodecompression limit the diver becomes saturated with
nitrogen and Group Designation Letters are no longer used.
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
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
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
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
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
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
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.
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.
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
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
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
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
Self Study Questions
______ stops are recommended while
______ stops are required by the dive
tables.
• Decompression / safety
• Safety / omitted
• Safety / decompression
• Precautionary / scheduled
Self Study Questions
______ stops are recommended while
______ stops are required by the dive
tables.
• Decompression / safety
• Safety / omitted
• Safety / decompression
• Precautionary / scheduled
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.
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.
Self Study Questions
Unlike Dive Tables, Dive Computers
calculate a dive profile in "real time";
compute "multilevel dives"; and have
automatic dive log functions.
a.True
b.False
Self Study Questions
Unlike Dive Tables, Dive Computers
calculate a dive profile in "real time";
compute "multilevel dives"; and have
automatic dive log functions.
a.True
b.False
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.
a.True
b.False
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.
a.True
b.False