Dive Tables Overview

7/27/2019 Dive Tables Overview

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NAUI Dive Tables


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Objectives

Describe the function of the dive tables.

Define common dive tables terminologyand 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 Intervalsfor repetitive dives.

Determine contingency mandatorydecompression stops.


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Purpose of the dive tables

Track the amount of Nitrogen you

accumulate in your body during a series ofdives.

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 ofdecompression sickness (DCS)


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Tables terminology and concepts

Dive Schedule/Dive Profile

Abbreviated statement of depth and time 70/40=70 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 givendepth without requiring a mandatory decompressionstop.


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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 ofthe SIT

Adjusted Maximum Dive Time

The maximum dive time for a repetitive dive toa given depth.

Total Nitrogen Time (TNT)

Represents total nitrogen load in your body atthe 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 of40 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 the Max depth,

followed by a 2-minute stop at a depth of15 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 decompressionstop.

Considered beyond the realm of sport diving risk and special equipment considerations.

However you should have contingency informationand be familiar with the minimal emergencyprocedures in case the maximum recreational divetime 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 oftime that includes the time spent on the

surface.

Follow that column to the right to your newgroup 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 theplanned depth of repetitive dive.

The box at the intersection of the column for planneddepth and the row for new letter group designationprovides:

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 onActual 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 youare 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 theAMDT 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 highestletter designation that will allow 20 minutes at 80feet.

In our example it is the letter C.

Continue working to the right until you find theintersection for the row C (the letter designationyou must become), and the column for letter F at

the bottom of table 1. (F is your currentdesignation as given in the example.)

The box at the intersection of row C from table 3and column F from table 1 indicates the SIT

necessary to change from an F diver to a Cdiver. In this case it is 2:59 4:25, so we mustwait a minimum of 2:59.


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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 thetables.

For example:

Dive 1 SIT Dive 2 = on the tables

60/40 0:08 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/23minutes

The diver must spend 5 minutes at 15 feet Note that any time from 22:01 25:00 requires this

stop


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A diver has a dive schedule of 100 feet for35 minutes

The diver must spend 15 minutes at 15 feet.Any time from 25:01 40:00 requires this

stop.

The actual stage decompression tables forair diving are extensive. The informationprovided here is for contingency purposesonly.

Stage decompression diving requiresextensive training and equipment, and isbeyond the realm of recreational diving.


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Before the Dive

Prior to entering the waterfor any dive you mustask yourself, and answer, the followingquestions:

How much excess Nitrogen, if any, do I have leftin 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 ofthe dive?

First dive in a sequence Maximum dive time (MDT). Repetitive dives Adjusted Maximum Dive Time

(AMDT).


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Post Dive

Afterthe 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 determineend-of-dive letter group.

Maximizes Bottom time or minimizes SIT

Minimizes the risk of DCS

Date post:	14-Apr-2018
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Dive Tables Overview

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