NAUI Dive Tables

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NAUI Dive Tables
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• Objectives
• Describe the function of the dive tables.
• Define common dive tables terminology and
  concepts.
• Explain the function and use of each individual
  table within the dive tables.
• Plan repetitive dives not requiring stage
  decompression.
• Calculate the minimum Surface Intervals for
  repetitive dives.
• Determine contingency mandatory decompression
  stops.

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• Purpose of the dive tables
• Track the amount of Nitrogen you accumulate in
  your body during a series of dives.
• Minimize the risk of Decompression sickness.
• Set time and depth limits such that you can make
  a direct ascent to the surface with minimal
  increase in the risk of decompression sickness
  (DCS)

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• Tables terminology and concepts
• Dive Schedule/Dive Profile
• Abbreviated statement of depth and time
• 70/4070 feet for 40 minutes
• Actual Dive Time (ADT)
• Surface to surface time, not including safety
  stop.
• Depth
• Deepest point of dive no matter how brief the
  time spent there.
• Maximum Dive Time (MDT)
• Maximum time you can spend on a dive to a given
  depth without requiring a mandatory decompression
  stop.

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• End-of-Dive Letter Group
• Symbol representing amount of excess nitrogen in
  your body at the end of the dive.
• Surface Interval (SIT)
• Time on surface between dives.
• During the SIT you are getting rid of some excess
  nitrogen (outgassing) and therefore your letter
  group, will change.
• New Group
• Letter group at the end of the SIT
• Repetitive Dive (Rep Dive)
• Any dive made within 24 hours of a preceding dive.

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• Residual Nitrogen Time (RNT)
• Excess Nitrogen in your body after a dive
• Represented by your new group at the end of the
  SIT
• Adjusted Maximum Dive Time
• The maximum dive time for a repetitive dive to a
  given depth.
• Total Nitrogen Time (TNT)
• Represents total nitrogen load in your body at
  the end of a dive
• Determined by combining RNT ADT T NT

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• Safety Stop
• Voluntary stop at the end of every dive
• Facilitates outgassing of Nitrogen
• Reduces the likelihood of bubble formation
• Mandatory Decompression Stop (Deco stop)
• Required stop at 15 feet whenever MDT or AMDT has
  been exceeded
• Beyond the training of recreational diving

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• Rules for Using the NAUI Tables
• Rate of ascent
• 1/2 foot per second or slower.
• Depth
• Use exact or next greatest number.
• Time
• Use exact or next greatest number
• Dive sequence
• Deep to shallow recommended
• During the dive
• For any rep. dive
• SIT
• Minimum recommended 1 hour
• Minimum recognized 10 minutes
• Keep activity to a minimum
• Drink water

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• Depth limit recommendations
• Sport Diving Maximum Depth 130
• Altitude Diving
• Special training/tables required when diving at
  altitudes above 1000 feet.
• Flying after diving
• 1 recreational dive 12 hours
• Multiple recreational dives 18 hours
• Mandatory Decompression dive 24 hours
• Long, cold, strenuous dive
• Use next greater TNT

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• Safety stops
• Maintain mouth at 15'
• Minimal activity throughout the stop.
• Protocols
• Dives with a max depth of 40 feet
• 3-minute stop at a depth of approximately15 feet.
• Dives with a max depth deeper than 40 feet
• initial 1-minute stop at a depth equal to ½ the
  Max depth,
• followed by a 2-minute stop at a depth of 15
  feet.
• For example, on a dive to 100 feet of seawater
  (FSW),
• make a 1-minute stop at a depth of approximately
  50 feet,
• followed by 2-minute stop at a depth of
  approximately 15 feet.

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• Stage Decompression Diving
• Dives that require a mandatory decompression
  stop.
• Considered beyond the realm of sport diving
• risk and special equipment considerations.
• However you should have contingency information
  and be familiar with the minimal emergency
  procedures in case the maximum recreational dive
  time is exceeded.
• Omitted Decompression
• Missed mandatory decompression stop and no
  symptoms
• Rest, drink fluids, and watch for signs of DCS.
• Do not re-enter water for at least 24 hours.
• If signs/symptoms of DCS are present treat for DCS

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• Table 1 End-of-Dive Letter Group
• Function
• Provide MDT for initial dive in sequence
• Provide end of dive letter group after any dive
• Use
• Find depth of dive in left hand column
• Follow row for that depth to the right and find
  TNT
• Follow column for TNT down to find end of dive
  letter group
• Circled numbers indicate the maximum TNT you can
  accumulate for a dive to a given depth without
  the need for a mandatory decompression stop
• Either for one dive or over a series of dives

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• Table 2 Surface-Interval-Time (SIT) Table
• Function
• Track SIT
• Use
• Follow column for end of dive letter group
  designation down until you find the block of time
  that includes the time spent on the surface.
• Follow that column to the right to your new group
  designation in table 3.

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• Table 3 Repetitive Dive Timetable
• Function
• Provide new letter group designation
• Provide Adjusted Maximum Dive Time (AMDT)
• Provide Residual Nitrogen Time (RNT)
• How to Use Table 3
• Find the row for your new group designation.
• Follow this row to the left to the column for the
  planned depth of repetitive dive.
• The box at the intersection of the column for
  planned depth and the row for new letter group
  designation provides
• RNT Top number
• AMDT Bottom number
• Use this information to plan your dive.

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• Determining the End-of-Dive letter group
  designation for a rep dive
• Based on
• Actual depth of the dive
• TNT (RNT TNT)
• Go to Table 1 End-of-Dive Letter Group
• Find the actual depth of your dive in column 1
• Follow the row for that depth to the right until
  you find the TNT.
• Follow this column down to find your end of dive
  letter group.

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• Planning a minimum SIT
• This process involves working backward from table
  3.
• Used when you must plan a minimum SIT between rep
  dives.
• For example at the end of your dive you are an F
  diver and you want to go to 80 feet for 20
  minutes. How long must you wait.

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• Look at table 3 Repetitive Dive Timetable
• Find the column for 80 feet
• Follow the column down until you find the AMDT
  closest to but still greater than 20 minutes.
• Remember the AMDT is the bottom number in the
  box.
• In our example it is the third box down which
  shows
• RNT 13
• AMDT 22

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• Follow that row to the right to find the highest
  letter designation that will allow 20 minutes at
  80 feet.
• In our example it is the letter C.
• Continue working to the right until you find the
  intersection for the row C (the letter
  designation you must become), and the column for
  letter F at the bottom of table 1. (F is your
  current designation as given in the example.)
• The box at the intersection of row C from table 3
  and column F from table 1 indicates the SIT
  necessary to change from an F diver to a C diver.
  In this case it is 259 425, so we must wait a
  minimum of 259.

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• SIT of less than 10 minutes
• Two dives separated by a SIT of less than 10
  minutes are considered one dive on the tables.
• For example
• Dive 1 SIT Dive 2 on the tables
• 60/40 008 50/30 60/70

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• Mandatory Decompression Stops
• Found in table 1
• Boxes to the right of the circled numbers
• Top number
• Indicates ADT requiring Mandatory Deco stoop
• Bottom number
• minutes that must be spent at 15 feet
• Example
• A diver has a dive schedule of 100 feet/23
  minutes
• The diver must spend 5 minutes at 15 feet
• Note that any time from 2201 2500 requires
  this stop

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• A diver has a dive schedule of 100 feet for 35
  minutes
• The diver must spend 15 minutes at 15 feet.
• Any time from 2501 4000 requires this stop.
• The actual stage decompression tables for air
  diving are extensive. The information provided
  here is for contingency purposes only.
• Stage decompression diving requires extensive
  training and equipment, and is beyond the realm
  of recreational diving.

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• Before the Dive
• Prior to entering the water for any dive you must
  ask yourself, and answer, the following
  questions
• How much excess Nitrogen, if any, do I have left
  in my body from previous dives?
• Residual Nitrogen Time or RNT
• What will be the maximum depth of my dive?
• What is my time limit for the planned depth of
  the dive?
• First dive in a sequence Maximum dive time (MDT).
• Repetitive dives Adjusted Maximum Dive Time
  (AMDT).

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• Post Dive
• After the dive you must ask yourself, and answer,
  the following questions
• What was the maximum depth of my dive?
• How long did I stay under water?
• Actual Dive Time (ADT).
• What is the total Nitrogen load in my body?
• Total Nitrogen Time (TNT).
• What is my end of dive letter group?

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• Proper use of the dive tables includes
• Using the tables pre-dive to plan the dive.
• Using the tables post dive to determine
  end-of-dive letter group.
• Maximizes Bottom time or minimizes SIT
• Minimizes the risk of DCS