# tdi advanced nitrox by G9Fnone

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Billy Hammond
#10407
Welcome to

Nitrox Review

Equipment Requirements

•Extension of Time
•Decompression Gas
Physical Principals
Of Diving

Pressure & Pressure Effects!

•   Equalizing
•   Buoyancy
•   Dive Time
•   No Deco Limits
•   MOD

Depth + Pressure = STRESS
Units Of Atmosphere

1 ATA =

760 mmHg = 14.696 psi = 1.0132 bar etc

Atmosphere vs. Atmosphere Absolute

33 fsw approximately = 10 metres = 1 BAR
Depth Vs. Pressure

Depth          Depth       Pressure
(fsw)         (metres)      (BAR)
Surface              1 BAR
33              10         2 BAR
66              20         3 BAR
99              30         4 BAR
132              40         5 BAR
165              50         6 BAR

Pressure (ATA) = (Depth ÷ 33 fsw) +1
Pressure (BAR) = (Depth ÷ 10 metres) +1
Pressure Vs. Volume

Depth             Pressure    Volume
(fsw)        (metres)       (BAR)          (size)
Surface               1              1
33               10          2             1/2
66               20          3             1/3
99               30          4             1/4
132              40          5             1/5
165              50          6             1/6

Simply Stated:
“Volume is inversely related to pressure”
Formula:         P1 × V1 = P2 × V2
Boyle’s Law

Problem: A Flexible container has 57 litres of air at 15
metres. How much will the volume change if it is taken to
28 metres?

Solution:
Step 1: Change depths to BAR:
15 metres = 2.5 BAR
28 metres = 3.8 BAR

Step 2: Re-work formula to solve for V2:
P1 × V1 ÷ P2 = V 2

Step 3: Solve:
2.5 BAR × 57 litres ÷ 3.8 BAR = 37.5 litres
Dalton’s Law

Ptotal = Pgas1 + Pgas2 +Pgas3 … Pgas(n)

or

“The whole is equal to the sum
of all the parts”

Air =
21% Oxygen
78% Nitrogen
1% Other Stuff (mostly argon)

Pressure of a gas =
Pg = Pt × fg
Total pressure × fraction of gas
Dalton’s Law

Table 4 ~ Depth, Pressure and Gas Pressures Air and Nitrox

Depth         Total             Air                    EAN32                  EAN40

Pressure
fsw     metres               Nitrogen      Oxygen   Nitrogen    Oxygen     Nitrogen    Oxygen
(BAR)

Surface            1        0.79          0.21     0.68           0.32    0.60           0.40

33           10      2        1.58          0.42     1.36           0.64    1.20           0.80

66           20      3        2.37          0.63     2.04           0.96    1.80           1.20

99           30      4        3.15          0.84     2.72           1.28    2.40           1.60

132           40      5        3.95          1.05     3.40           1.60      --            --

165           50      6        4.74          1.26       --            --       --            --
Dalton’s Law

Table 4 ~ Depth, Pressure and Gas Pressures Air and Nitrox
5                                     ~ EAN40, EAN60 and EAN80

Depth         Total           Air
EAN40                  EAN32
EAN60                  EAN40
EAN80

Pressure
Pressure
fsw
fsw    metres
metres              Nitrogen
Nitrogen   Oxygen
Oxygen   Nitrogen
Nitrogen    Oxygen
Oxygen     Nitrogen
Nitrogen    Oxygen
Oxygen
(BAR)
(BAR)

Surface         1.0        .60         .40     .40            .60     .20            .80
Surface          1        0.79        0.21    0.68           0.32    0.60           0.40
10       3       1.3       0.78        0.52    0.52           0.78    0.26           1.04
33      10        2        1.58        0.42    1.36           0.64    1.20           0.80
20       6       1.6       0.96        0.64    0.64           0.96    0.32           1.28
66      20        3        2.37        0.63    2.04           0.96    1.80           1.20
33      10       2.0       1.20        0.80    0.80           1.20    0.40           1.60
99
55      30
16.6       4
2.67       3.15
1.60        0.84
1.07    2.72
1.07           1.28
1.60    2.40
--           1.60
--
132
66        40
20      5
3.0       3.95
1.80        1.05
1.20    3.40
1.20        1.60
(1.80)        --
--            --
--
165
99         50
30      6
4.0       4.74
2.40        1.26
1.60      --            --       --            --
Dalton’s Law

Table 5 ~ Depth, Pressure and Gas Pressures ~ EAN40, EAN60 and EAN80
Example: EAN 60 at 10 metres has corresponding
Depth         Total           gas
EAN40 pressures of:
EAN60           EAN80
Pressur
metre
fsw                  e      Nitrogen   Oxygen    Nitrogen   Oxygen   Nitrogen   Oxygen
s
(ATA)
Surface            1.0       .60       .40        .40       .60       .20       .80
10           3      1.3      0.78       0.52      0.52       0.78     0.26       1.04
Oxygen: 2 BAR × .60 = 1.20 BAR
20           6      1.6      0.96       0.64      0.64       0.96     0.32       1.28
33           10     2.0      1.20       0.80Nitrogen: 2 BAR × .40 = .80 BAR 1.60
0.80    1.20      0.40
55       16.6      2.67      1.60       1.07      1.07       1.60       --        --
66           20     3.0      1.80       1.20      1.20      (1.80)      --        --
99           30     4.0      2.40       1.60        --        --        --        --
Dalton’s Law

Maximum Operating Depth
(MOD)
Depth is the same as Pressure so…
Pressure (Total) can be converted to Depth
Pg
Pressure of the gas
Pt
Pressure Total = =
fg
Fraction of the gas

Best Mix
Pressure of the gas
Pg
fg
Fraction of the gas =
Pt Pressure Total
Dalton’s Law

How Dose?
Best Mix?
What Deep?

Pg

=        =×
fg        Pt
Equivalent Air Depth

Step 1: How Much Nitrogen?
fN2 = 1 – fO2

Step 2: How much N2 compared to air?
Ratio = (1 – fO2) ÷ 0.79

Step 3: Convert to absolute depth!
Absolute Depth = Actual Depth + 10 metres

EAD “absolute” = Absolute Depth × Ratio

FN2
.79

FN2
.79
Physical Principals
Review

1. What is the absolute pressure at 28 metres?
(28 ÷ 10) + 1 = 3.8 BAR

2. What is the depth at an absolute pressure of 3.1 BAR?
(3.1 - 1) × 10 = 21 metres

3. What is the pressure of oxygen of EAN45 at 19 metres?
((19 ÷ 10) + 1) × .45 = 1.3 BAR PO2
Physical Principals
Review

4. What is the pressure of nitrogen of EAN28 at 43 metres?
((43 ÷ 10) + 1) × (1 - .28) = 3.8 BAR

5. At what depth does the pressure of oxygen of normal air reach 1.6 BAR?

((1.6 ÷ .21) – 1) × 10 = 66.19 metres
Physical Principals
Review

6. What is the MOD of:
EAN28
((1.6 ÷ .28) - 1) × 10 = 47.1 metres
EAN40
((1.6 ÷ .4) - 1) × 10 = 30 metres
EAN50
((1.6 ÷ .5) - 1) × 10 = 22 metres
EAN60
((1.6 ÷ .6) - 1) × 10 = 16.6 metres

7. What is the EAD of EAN50 at 21 metres?
((1 - .5) ÷ .79) × (21 + 10) - 10 = 9.6 metres
Physiological Principles
of Diving

Physiology is exceptionally complex

Body responds to nitrogen and
oxygen as if they are DRUGS

2 problems with diving:
DCS and CNS O2 Toxicity

Time and Dose relationship
Nitrogen

Properties of Nitrogen

If anything seems wrong…
IT IS WRONG!!!
Surface NOW!

Decompression Illness:
Type I – Pain Only Bends
Type II – Central Nervous System

Dehydration is the leading cause of DCS
Oxygen

Properties of Oxygen

Hypoxia               OTUs
Hyperoxia           CNS Toxicity

ConVENTID

NOAA O2 Exposure Chart
Carbon Dioxide

CO2 Convulsions

CO2 Sources

Deleterious Effect

Worsens Narcosis
CO2 Sources

Compressor Intakes
Poor Compressor Maintenance
Improper Blending Techniques

Problems:

Colorless, Odorless, Tasteless:
Hemoglobin Bonding
Unconsciousness > Death
Physiological Principals
Review

1. What are the two pressure effects of nitrogen on the human body?
Nitrogen Narcosis and Decompression Sickness

2. What should the diver do if “nitrogen narcosis” is suspected?
Ascend or abort the dive

3. Does Nitrox eliminate the need to plan dives and the “bends”?
Absolutely NOT

4. Is using Nitrox “safer” than using “air”?
No, not necessarily, oxygen toxicity is a concern

5. Can the diver predict the onset of an oxygen convulsion?
No, the diver can only plan to avoid
6-10
Physiological Principals
Review

6. Is diving at a pressure of oxygen of 1.3 BAR “safer” than 1.4 BAR?
Only in the sense it may take longer to convulse, otherwise no, it is not “safer”

7. What are the two types of oxygen toxicity?
Pulmonary and Central Nervous System
8. Which type of oxygen toxicity is of primary concern to the Nitrox diver?
Central Nervous System – convulsions
9. List three conditions that carbon dioxide can cause or make worse:
b. Increased narcosis
c. Increased oxygen toxicity

10. Why is carbon monoxide considered a major hazard?
It binds with the hemoglobin of the blood and prevents oxygen from getting to the
tissues
Dive Planning

Accident Analysis

What If….?

Computer Loss

Gas Loss

Reduced nitrogen absorption
Shortens deco time
Increases N2 elimination

Planning Considerations:
Tables / Computers
Pony Bottles
Different gases and reasoning
Computer generated dive tables
Multimix dive computers
Gas Requirements

SAC Rate
Surface Air Consumption Rate
(also SCR, Surface Consumption Rate)

Determining SAC Rate:
1. Determine bar used
2. Determine litres used
3. Determine time
4. Determine litres used per minute
5. Convert litres used per minute at depth
(BAR) to SAC (SCR)
Dive Tables

Use the table of choice:
USN, Sport, DCEIM, Buhlmann …

3 Sections

1. No Deco Table
2. Surface Interval Table
3. Residual Nitrogen Table

DO NOT MIX TABLES!
Dive Tables

SECOND LETTERS &BOTTOM (NOTE GAS USED)
RECORD DEPTH AND DIVE LETTER TIME
TOTAL RECORD ACTUAL DEPTH
FINAL BOTTOM & DECO GAS DIVE
SAFETY AND/OR NOTE INTERVAL
DETERMINE TIME FOR 2
TOTAL SURFACE STOP(S)
STOP(S) START
START            SIT

TBT:               ABT:
+RBT:
=TBT:
Pitfalls of Tables

Major Pitfall?
… The Diver!!!

No Multi-Level Tracking

Inaccurate Time Tracking

Inaccurate Depth Tracking
Nitrox Tables

Based on Standard Tables & Mixes
(Typically EAN32 & EAN36)

Ease Of Use

No Calculation Errors

(Imperial)

Air
.21   .22   .23   .24   .25    .26   .27   .28   .29
Table
30     30    30    31    32    33     34    35    36    37
40     40    40    41    42    43     44    46    47    48
50     50    51    52    53    54     55    56    58    59
60     60    61    62    63    64     66    67    69    70
70     70    71    72    74    75     76    78    80    81
80     80    81    82    84    86     87    89    90    92
90     90    91    93    94    96     98    100   101   103
100     100   101   103   105   107    108   110   112   114
110     110   111   113   115   117    119   121   123   126
(Metric)

Air
.21   .22   .23   .24   .25    .26   .27   .28   .29
Table
9      9     9     9     10    10     10    11    11    11
12     12    12    13    13    13     13    14    14    14
15     15    15    16    16    16     17    17    17    18
18     18    18    19    19    19     20    20    21    21
21     21    21    22    22    23     23    24    24    24
24     24    24    25    25    26     26    27    27    28
27     27    27    28    28    29     29    30    31    31
30     30    31    31    32    32     33    33    34    34
33     33    34    34    35    35     36    37    37    38
MOD Tables
(Imperial)

Air
.21   .22   .23   .24   .25     .26   .27   .28   .29
Table
30     30    30    31    32    33      34    35    36    37
40     40    40    41    42    43      44    46    47    48

140     140   142   144   146   149    151    154   156   159
MOD
1.4    187   177   167   159   151    144    138   132   126
1.6    218   207   196   187   178    170    162   155   149
MOD Tables
(Metric)

Air
.21   .22   .23   .24   .25    .26   .27   .28   .29
Table
9      9     9     9     10    10      10   11    11    11
12     12    12    13    13    13      13   14    14    14

42     42    43    43    44    45      45   46    47    48
MOD
1.4    57    54    51    48    46      44   42    40    38
1.6    66    63    60    57    54      52   49    47    45
PO2 Table
(Imperial)

PO2   O2 Time   .21   .22   .23   .24   .25    .26   .27

1.0    300      124   117   110   104   99     93    89
1.1    240      139   132   124   118   112    106   101
1.2    210      155   147   139   132   125    119   113
1.3    180      171   162   153   145   138    132   125
1.4    150      187   177   167   159   151    144   138
1.5    120      202   192   182   173   165    157   150
1.6     45      218   207   196   187   178    170   162
PO2 Table
(Metric)

PO2   O2 Time   .21   .22   .23   .24   .25   .26   .27

1.0    300      38    36    33    32    30    28    27
1.1    240      42    40    38    36    34    32    31
1.2    210      47    45    42    40    38    36    34
1.3    180      52    49    47    44    42    40    38
1.4    150      57    54    51    48    46    44    42
1.5    120      61    58    55    53    50    48    46
1.6     45      66    63    60    57    54    52    49
Dive Planning
Review

1. What is the Surface Air Consumption rate of a diver that has the following data:
    Depth:                  12 metres
    Cylinder:               2830 L@227 bar
    Start PRESSURE:         145 bar
    End PRESSURE:           117 bar
    Time:                   4 minutes

     Aluminum 227 bar = 12.467 litres per bar (12.5 litre cylinder)

     Used 28 bar in 4 minutes = 7 bar / minute

     7 bar/min. × 12.467 litres/bar = 87 litres per minute

     12 metres = 2.2 BAR
     87 ÷ 2.2 = 40 litres of gas per minute (rounded for safety)
Dive Planning
Review

2. Show the Dive Plan and profile for an Air dive to 23.5 metres for 34 minutes, 3:21 Surface
Interval, and a second dive to 16 metres for 36 minutes. Show all residual nitrogen
categories.

AIR                      H         3:21         C                       J

TBT :34                               ABT:         :36
+RBT:         :17
=TBT:         :53
Dive Planning
Review

3. What is the best mix for a dive to 20 metres and not exceed an oxygen pressure of 1.4 BAR.

1.4 ÷ (20 ÷ 10 + 1) = .47 or EAN 47

Depth, Mix and PO2 Table (Metric)

PO2       O2 Time      .44      .45      .46.      .47      .48       .49      .50

1.3        180        20        19       18       18        17       17        16
1.4        150        22        21       20       20        19       19        18
1.5        120        24        23       23       22        21       21        20
Dive Planning
Review

4. Show the Dive Plan and profile for a Nitrox dive to 25 metres for 38 minutes, 2:18
Surface Interval, and a second dive to 19.5 metres for 48 minutes. Choose the Best
Mix with an oxygen pressure of 1.4 BAR at the maximum depth. Use the same mix for
both dives. Show all residual nitrogen categories.

a.   Using the EAD Tables, the best mix for 25 metres at 1.4 BAR oxygen exposure is
EAN 40.

b.   Using the EAD Tables, the EAD of EAN 40 at 25 metres is 18 metres. (note there
may be a “rounding” difference in depths between imperial and metric EAD
tables)
Dive Planning
Review

4c. USN Tables & USN Modified Tables (in this case using either of these tables results in
the same answer, but note the difference using the metric tables.)

EAN 43                   F (G)       2:18        D (E)                    I

25 metres                           19.5 metres

18 metres                              12 metres

TBT :38                                 ABT:        :48       :48
+RBT:        :37       :49
=TBT:        :85       :97
Dive Planning
Review

4c. DCIEM Tables

E (E)
EAN 43                 F (E)    2:18     × 1.3 (1.4)

25 metres                        19.5 metres

18 metres                         12 metres

TBT :38                              ABT:       :48     :48
× modifier:   × 1.3   × 1.4
=TBT:     :62.4   :67.2
Dive Planning
Review

4c. Buhlmann Tables

E (E)
EAN 43               E (E)    2:18

25 metres                      19.5 metres

18 metres                       12 metres

TBT :38                           ABT:   :48
+ RBT:   :19
=TBT:   :67
Dive Planning
Review

5. How much gas would the diver in Question 4 require for the second dive assuming an
average SAC rate of 25.5litres/min ?

a.   Convert 19.5 - to BAR:

(19.5 + 10) ÷ 10 = 2.95 BAR

b.   Determine gas used:

2.94 BAR × 25.5 l / min × 48 minutes = 3611 litres.
Equipment Considerations

< EAN40       vs.     > EAN40
(cleaning, lubricants, materials)

Oxygen doesn’t burn, FUEL burns
(oxygen just promotes combustion)

(production of toxic gasses)

High-pressure vs. Low-pressure
(system components)
Equipment Markings

Regulator Identification

Cylinder Markings
(Oxygen, Nitrox, Argon, Contents)

Cylinder Certifications
(Eddy, VIP/CIP, Hydro, Oxygen Clean)
Oxygen Analysis

Components Of Analysis
Fuel Cell
Analysis Unit
Flow Containment System

Analyzer Setup (Demonstration)
Nitrox Production

Partial Pressure

Membrane Separation

Continuous Blending
Equipment Considerations
Review

1. Oxygen cleaning means to remove what material?
Hydrocarbon (oil/grease) contaminations

2. Oxygen cleaning is required for mixes above what percentage?
Above 40 percent for all equipment - Any percentage for cylinders

3. Opening a valve slowly, reduces what problem?
Adiabatic compression – high temperatures due to sudden pressure increases – may
cause fire or worse, produce carbon monoxide

4. What three markings are required of a Nitrox cylinder?
Cylinder Identification, Inspection Label and Contents Label
Equipment Considerations
Review

5. Who is responsible to ensure the analysis of a Nitrox cylinder?

The DIVER!

6. Does an oxygen analyzer measure the “fraction” of oxygen or the “pressure” of
oxygen?

It measures PARTIAL PRESSURE (unless of course you have access to mass
spectrometers!)

7. Name at least two methods of producing Nitrox.

Partial Pressure Blending and it various forms, Membrane separation techniques,
Continuous Blending
Equipment Considerations
Review

8. What color is commonly used for regulator covers used with high values of Nitrox or
oxygen?

Nitrox second stage regulator covers tend to be yellow and Oxygen (or mixes
above 40% in some cases) tend to be green

9. To analyze a cylinder of EAN80, what gas should be used to calibrate the oxygen analyzer

Oxygen

10. Does a cylinder need to be oxygen cleaned to be used with EAN36?

Of course, cylinders are the exception for the 40 Percent Rule … since they may
be blended by the partial pressure technique
Congratulations!!!

Let’s Go Diving!!!

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