1. Submarines’ Atmosphere
Control and Air Treatment
Mohammed Dayraki
104357965
Underwater Intervention Systems
06-88-590-38/92-590-64 F15
Instructor:
Dr. Graham Reader
Leading Teaching Assistants:
Marko Jeftic
Kelvin Xie
Department of Electrical Engineering, Faculty of Engineering
University of Windsor
401 Sunset Avenue, Windsor, ON N9B 3P4

2. SUBMARINES’ ATMOSPHERE CONTROL AND AIR TREATMENT
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Abstract
This project looks at Submarines’ Atmosphere Control and Air Treatment. Its goal is to
focus on the systems used in underwater vehicles to supply oxygen, remove carbon
dioxide, and to purify the atmosphere in the vehicle. It also includes emergency air
systems in case of accidents. The project gives a general view about the need of oxygen
for a human and the statistics of oxygen level in a human and in seawater. One the 2
types of equations used in the paper shows how the studies where done and the other
type shows how every system work. The best climate a crewman should be in so there’s
no psychological or physical effects is highlighted in the paper and a general view about
the USS Pennsylvania Submarine is used. As a conclusion, food resupply is the only thing
preventing a submarine from staying forever underwater.

3. SUBMARINES’ ATMOSPHERE CONTROL AND AIR TREATMENT
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List of Contents
ABSTRACT……………………………………………………………………………..……….2
INTRODUCTION………………………………………………………………......……………4
AIM…………………………………………………………………………………….………….5
THE NEED OF OXYGEN……………………………………………………………...……….6
OXYGEN BLOOD LEVELS…………………………………………………………….………6
CONCENTRATION OF OXYGEN IN SEAWATER…………………………….……………6
DETERMINATION OF HENRY COEFFICIENT……………………………………..………7
CARBON DIOXIDE LEVELS IN THE AIR……………………………………………………9
CLIMATE OF THE ATMOSPHERE ………………………………………..…………………9
USS PENNSYLVANIA SUBMARINE…………………………………………………………9
ATMOSPHERE CONTROL AND AIR TREATMENT SYSTEMS…………………...……10
OXYGEN SUPPLY SYSTEMS……………………………………………………….………10
CARBON DIOXIDE REMOVAL………………………………………………………………12
AIR PURIFICATION………………………………………………………………...…………13
EMERGENCY AIR………………………………………………………………….…………14
HOW LONG CAN A SUBMARINE STAY UNDERWATER? …………………….………15
CONCLUSION…………………………………………………………………………………15
APPENDIX A…………………………………………………………………….…..…………16
APPENDIX B………………………………………………………………………...…………17
LIST OF REFERNCES…………………………………………………….….………………18
LIST OF DEFINITIONS, SYMBOLS AND ABBREVIATION………………………………19

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Introduction
Submarines’ Atmosphere Control and Air Treatment goes deep into a submarine’s air
control systems which include electrochemical oxygen generators, solid polymer oxygen
generators, oxygen candle furnace, LiOH absorbers, 𝐶𝑂2 scrubbers, 𝐶𝑂 − 𝐻2 burners,
activated carbon, emergency air breathing systems, oxygen breathing apparatus, and
Scott air packs. This paper explains how a submarine can stay underwater for 20 years
theoretically and 90 days in reality. The report reviews studies in human’s oxygen need,
seawater oxygen level, and chemical reactions and combines them so that submarines’
climate will be similar to the normal climate on land.

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Aim
The purpose of the project is to highlight the systems used in a submarine to supply 𝑂2
to the crew and remove the 𝐶𝑂2 from the air inside.

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The Need of Oxygen:
A human’s body uses many ways to extract energy from the surroundings so it can
survive. A major way is food which is is used as raw materials to make and heal body
cells. Another way is oxygen where our body use it to enrich all the organs a human
has. Upon inhaling, our lungs are filled up with air and alveoli absorb the oxygen into
our bloodstream. Hemoglobin then picks the oxygen to any organ in the body.
Cytochrome C then takes the oxygen molecules, mix them with water and, harvests the
released energy. The cell after that uses the energy for everyday function [1].
Oxygen Blood Levels:
The body of a human needs a very specific oxygen level in the blood. The normal
oxygen saturation in humans are considered 95-100 percent. Mayo clinic [2] defines
that hypoxemia is a result of oxygen level below 90 percent. If oxygen blood level is
under 80 percent, some organs will start malfunctioning including the brain and the
heart and continued low oxygen levels may lead to failure in respiratory or cardiac
systems.
Concentration of Oxygen in Seawater:
To calculate the standard atmospheric concentrations (USAC) in seawater, the equation
of henry coefficient as a function of temperature and salinity is used at a total pressure
of 1 atmosphere.

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Determination of the Henry Coefficient:
In system of standard composition saturated with water vapor at total pressure P,
Henry’s Law is:
𝑓𝑜 = 𝑘 𝑜,𝑠
𝑛 𝑜,𝑑
𝑛 𝑤+ 𝑛 𝑠 + 𝑛 𝑜,𝑑+𝑛 𝑟,𝑑
(1)
where 𝑓𝑜(atm) and 𝑘 𝑜,𝑠(atm) are the vapor phase fugacity and the Henry coefficient for
oxygen, and 𝑛 𝑜,𝑑 , 𝑛 𝑤, 𝑛 𝑠, and 𝑛 𝑟,𝑑 are the numbers of moles of dissolved oxygen, pure
water, sea salt, and the number of moles of all other gases especially nitrogen dissolved
in the volume V.
The concentration, by mass, of dissolved oxygen in 𝑚𝑜𝑙. 𝑘𝑔−1
is:
𝐶 𝑜
𝑝
≡
𝑛 𝑜,𝑑
𝑝 𝑠 𝑉𝑠
(2)
where 𝐶 𝑜
𝑝
is the standard atmospheric concentration of dissolved oxygen and 𝑛 𝑜,𝑑 , 𝑝𝑠 ,
and 𝑉𝑠 are the number of moles of dissolved oxygen, pressure of the system, and the
volume of it relatively.
t
( 𝑪𝒐
)
S
P
(atm*)
𝒌 𝒐,𝟎
(𝒂𝒕𝒎)
𝒌 𝒐,𝒔
(𝒂𝒕𝒎)
%dev of
𝒌 𝒐,𝒔 𝒇𝒓𝒐𝒎 𝒇𝒊𝒕
0.231 20.172 0.7754 25427 29332 0.054
0.228 31.634 0.7769 25425 31793 0.032
0.218 48.667 0.7842 25418 35806 -0.071
5.010 20.204 0.7950 28863 33097 0.069
5.023 31.703 0.7987 28873 35762 0.031
10.017 20.209 0.8131 32536 37095 0.091
10.029 31.639 0.8219 32545 49830 -0.186

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15.009 20.098 0.8408 36221 40977 -0.077
15.009 20.459 0.8399 36221 41155 0.134
15.011 31.750 0.8468 36222 44082 0.026
15.008 48.514 0.8546 36220 48917 0.085
25.038 20.089 0.9104 43488 48758 -0.056
25.033 31.894 0.9171 43484 52139 -0.07
29.993 31.894 0.9402 46922 55957 0.035
35.092 20.228 0.9710 50288 56054 0.016
35.081 31.856 0.9749 50287 59633 -0.026
35.006 49.478 0.9733 50239 65518 0.026
45.007 31.912 1.0464 56258 66167 0.075
Table.1: The variation of the Henry Coefficient 𝒌 𝒐,𝟎 for oxygen depending on the
variation of temperature, Salinity, and Pressure
18 samples were taken with variable temperatures, salinity, and pressure as shown in
table.1 to experience the difference of Oxygen concentration in the seawater. In the
experiment, “the salinity sample was taken after the vapor phase and liquid phase
samples had been isolated. The seawater used in these measurements was taken from
Buzzards Bay, off Massachusetts, filtered, and stored in the dark. The pH was
determined with a Corning model 10 meter and was constant within 8.2 ± 0.1” [3]. The
results for 𝑘 𝑜,𝑠 from 18 experiments on seawater samples with salinities up to 50 and at
temperatures between 0 and 45 𝐶𝑜
are in the table.

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Carbon Dioxide Levels in the Air:
“The air we breathe contains about about 0.03% of carbon dioxide (equivalent to a
partial pressure of about 30Pa) (Haux, 1981)” [4]. It will be hard to uphold such level in
an underwater vehicle. Once the CO2 reaches 4%, the atmosphere in the vehicle will be
lethal to humans. As a result, air treatment systems should maintain the carbon dioxide
level so the crew will stay have good mental and physical performance. For such
performance, a maximum partial pressure for carbon dioxide should be 1500Pa or 1.5%
CO2.
Climate of the Atmosphere:
The climate of a the vehicle is very important for which it define the physical and the
psychological stresses of the crew. In normal atmospheres, the temperature should be
between 18 and 22 𝐶𝑜
. Humidity should stay between 50% and 65% for best
performance. The problem is that heat is generated by all the process equipment so air
conditioning systems should be applied in the submarine.
USS Pennsylvania Submarine:
“You can’t see her, she can dive over 250 meters and stay down for 6 months. You
can’t hear her; she can run for 20 years without refueling. She is the most lethal weapon
ever designed.” [5] The USS Pennsylvania is an Ohio Class Submarine. It’s controlled
by a captain on deck and 165 men. The petrol that this submarine undergoes is about
72 days where the submarine stays underwater hiding. Once the hatch is closed, the
crew are sealed inside the Pennsylvania for the time of their mission. To stay alive,

10. SUBMARINES’ ATMOSPHERE CONTROL AND AIR TREATMENT
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every man needs oxygen and food. To produce oxygen, the USS submarine uses
Electrolysis in a very big scale using Oxygen Generators type H.P Serial no. 2139.
Atmosphere Control and Air Treatment Systems:
Nowadays, all Navy submarines are equipped with oxygen supply systems to maintain
proper atmospheric conditions and to remove contaminants. Controlling the source of
the materials is the most effective way of reducing and eliminating toxic contaminant.
Oxygen Supply Systems:
By using electrolysis oxygen generators (EDGs), stored oxygen, or oxygen candle
furnaces, oxygen may be refilled in an underwater vehicle. Nuclear submarines in
general are equipped with EOG systems but carry other systems as back up. One
specialty about EOG is that it can supply oxygen forever while other are limited by
storage capacity.
-Electrochemical Oxygen Generator:
Through electrolysis of water, oxygen is produced. By passing direct current through a
KOH solution, the water is electrolyzed to 𝐻2 and 𝑂2. Sixteen electrolytic cells at about
1000 amps are required to produce 120 SCFH of 𝑂2 which is sufficient for 120 men in
the submarine at a pressure up to 3000 psig. After that, gases are removed from all the
cells and 𝑂2 is distributed while 𝐻2 is discharged.
-Solid Polymer Oxygen Generator:
These type of generators are advanced technology oxygen generator where they
provide safe and reliable oxygen production. By using Solid Polymer Electrolyte (SPE)

11. SUBMARINES’ ATMOSPHERE CONTROL AND AIR TREATMENT
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cell, the oxygen generating Plant (OGP) produces breathing oxygen through electrolysis
which requires no free acids or caustic liquids. The pros of OGP are:
- It eliminates caustic electrolyte (KOH) and asbestos which is used as an
insulator.
- It’s controlled by a Microprocessor and requires only 15 minutes to shutdown and
restart to full operation.
- It can be operated at low pressure that can be 500-600 psi once oxygen banks
are charged.
- It has reduced inventory of combustible gases such as hydrogen
- It has a maximum output of 𝑂2 which is 225 SCFH. This will permits providing the
entire crew with oxygen using only one OGP
- Produces pure oxygen products without any 𝐻2 contamination
-Oxygen Candle Furnace:
The chlorate candle is a mixture of sodium chlorate, iron, a small amount of barium
peroxide, and a fibrous binding material. Burning the “Candle” is the basic process
where decomposition of the chlorate is applied:
𝑁𝑎𝐶𝑙𝑂3(𝑠) + 𝐹𝑒( 𝑠) → 𝑁𝑎𝐶𝑙(𝑠) + 𝑂2 (𝑔) + 𝐹𝑒( 𝑥) 𝑂(𝑦)(𝑠) (3)
Iron is combined with some oxygen and produces heat to support the reaction. To
remove unwanted chlorine products, barium peroxide is added:
𝐵𝑎𝑂2( 𝑥) + 𝐶𝑙2( 𝑔) → 𝐵𝑎𝐶𝑙2( 𝑠) + 𝑂2( 𝑔) (4)
2𝐵𝑎𝑂2(𝑥) + 4𝐻𝑂𝐶𝑙2( 𝑔) → 2 𝐵𝑎𝐶𝑙2(𝑠) + 3𝑂2(𝑔) + 2𝐻2 𝑂(𝑙) (5)
Each candle burns about 400 F for 45- 60 minutes, and yields 115 of 𝑂2 at 0.5 psig. By
filtration, smoke and salt are also produced.

12. SUBMARINES’ ATMOSPHERE CONTROL AND AIR TREATMENT
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Carbon Dioxide Removal:
CO2 is removed from the submarine by regenerative or non regenerative classes
depending on if the absorbent can be recycled at sea.
-𝐿𝑖𝑂𝐻 Absorbers:
It’s one of the non regenerative means to remove Carbon Dioxide from the gas torrent
that will pass through containers holding the 𝐿𝑖𝑂𝐻. Each 31.5 lb. container can absorb
29 lbs. of CO2 theoretically where it operates below 2% at 1 atm. total pressure and
requires no power even if it is sued with a fan when possible.
2𝐿𝑖𝑂𝐻 + 𝐶𝑂2 → 𝐿𝑖2 𝐶𝑂3 + 𝐻2 𝑂 (6)
-𝐶𝑂2 Scrubbers:
𝐶𝑂2 scrubbers are regenerative systems that use aqueous solutions of 25 – 30 wt. % (4-
5 M) monoethanolamine (MEA), NH2CH2CH2OH. Lewis acid-base reaction is the
process:
𝐻 − 𝑂 − 𝐶𝐻2 − 𝑁𝐻2 + 𝑂 = 𝑂 → 𝐻 − 𝑂 − 𝐶𝐻2 − 𝐶𝐻2 − 𝑁𝐻 − 𝐶𝑂 − 𝑂𝐻 (7)
Equation (7) will be stopped by heat or by low pressure atmosphere. Air treated should
enter the exchange tower at 80°F and 75% relative humidity CO2 (RH). It’s driven
through woven stainless steel which the MEA solution is flowing. At this phase, 70 to
90% of the Carbon Dioxide is removed. After that, the air is filtered to entrap droplets of
the MEA solution and then it’s returned to the submarine at about 75°F and 100%.
Stainless steel screens are used to recycle the MEA solution. The material is passed
through a column packed with glass rings and is heated to drive off the carbon dioxide

13. SUBMARINES’ ATMOSPHERE CONTROL AND AIR TREATMENT
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under pressure. When the solution is clean, it’s returned to the absorption cycle and the
CO2 is cooled and thrown overboard.
Carry-over of MEA and ammonia are problems in this systems. They are created when
the MEA slowly breaks down during the stripping phase to the submarine’s atmosphere
with the cleaned air. The decomposition of MEA is also catalyzed by the presence of
metal ions so chelating agents are added to limit this degradation. Materials escapes
into the submarine even after filtering.
Air Purification:
𝐶𝑂 − 𝐻2 Burner:
Burners are used to oxidize CO, H2, and hydrocarbons into to CO2 and H2O. It’s done
by drawing preheated air through CuO/MnO2 catalyst bed at about 600° F. When these
gases cool down, they are passed through a layer of Li2CO3 so acidic gases like HCI
will be eliminated. The last stage is done when air is passed through activated charcoal,
a simple absorber. Charcoal can be used forever and it does not need additional fuel
once it has reached operating temperature.
Activated Carbon:
To prepare charcoal, you can use any carbonaceous material and it can be activated by
the use of controlled heating. Through heating the capillaries, which can’t be
carbonized, are removed. When the charcoal is activated, increase in the vapor
adsorption is noticed. In submarines, the activated coconut shell charcoal is referred to
as activated carbon. Removing contaminant gases is a difficult phenomenon involving

14. SUBMARINES’ ATMOSPHERE CONTROL AND AIR TREATMENT
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capillary attraction and adsorption. Activated carbon is basically used for odor removal
in washroom, water closet, sand sanitary tanks.
Emergency Air:
Emergency Air Breathing (EAB) System:
The EAB system is used in case of fire with development of smoke, CO, CO2, or in
case of toxic component detection. This system provides full-face masks for each crew
member into the ship’s clean, high pressure air banks and hoses and pressure
reduction gear are part of the EAB system.
Oxygen Breathing Apparatus (OBA):
It’s a self-contained unit that is worn by each person and can generate to 60 minutes
supply of oxygen and removes exhaled carbon dioxide. It functions by decomposing
potassium superoxide KO2.
4𝐾𝑂2(𝑠) + 2𝐻2 𝑂(𝑔) → 𝐾𝑂𝐻(𝑠) + 3𝑂2(𝑔) (8)
Equation (8) is initiated by water vapor exhaled by the wearer of the system. KOH
produced will interact by K2O and removes the CO2 from the air as Eq. (9) shows.
𝐶𝑂2(𝑔) + 2𝐾𝑂𝐻(𝑔) → 𝐾2 𝐶𝑂3(𝑔) + 𝐻2 𝑂(𝑔) (9)
Rebreathing is allowed in this system since it uses only a fraction of Oxygen.
SCBA – Scott Air Packs:
Scott Air Packs are the same system used for SCUBA but it’s created for the air
environment. It’s rechargeable, portable, and it’s used sometimes as a replacement for
OBAs.

15. SUBMARINES’ ATMOSPHERE CONTROL AND AIR TREATMENT
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How long can a Submarine stay Underwater?
Nuclear- powered submarines stay underwater for long periods which can last for
several months and that’s because of the oxygen generating and atmosphere control
systems for breathing and nuclear power for the submarine itself. Food and supplies are
the only reasons for the submarine to come back to the base. A normal submarine
carries 90-day supply of food.
Conclusion
As a conclusion, Submarines and especially nuclear- powered ones are stealthy
monsters that have the ability to stay underwater forever if it wasn’t for the crew inside
it. “You can’t see her, she can dive over 250 meters and stay down for 6 months. You
can’t hear her; she can run for 20 years without refueling. She is the most lethal weapon
ever designed.” [5] One of the solutions for this problem is treating crewmen like
astronauts so they’ll have more space for more food supplies.

16. SUBMARINES’ ATMOSPHERE CONTROL AND AIR TREATMENT
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Appendix A: Normal Amount of Substances in the Atmosphere
Substance 8-h weighted
Average Limit
(ppm)
Ceiling
concentration
Ammonia 50
Carbon Dioxide 5000
Carbon Monoxide 50
Freon-12 1000
Hydrogen Chloride 5
Hydrogen Fluoride 3
Mercury 0.1 mg/𝑚3
Nitric Acid 25
Nitrogen Dioxide 5
Oil Mist 5 mg/𝑚3
Ozone 0.1
Phosgene 0.1
Stibene 0.1

17. SUBMARINES’ ATMOSPHERE CONTROL AND AIR TREATMENT
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Appendix B: Line Drawing of an Ohio Class in its original SSBN configuration
1-Sonar Dome
2- Main Ballast Tanks
3- Computer Room
4-Integrated Radio Room
5-Sonar Room
6-Command and Control Center
7-Navigation Center
8-Missle Control Center
9-Engine Room
10-Reactor Compartment
11-Auxillairy Machinery Room no.1
12-Crew’s Berthing
13-Auxiliary Machinery Room no.2
14-Torpedo room
15-Wardroom
16-Chief Petty Quarters
17-Missle Compartment

18. SUBMARINES’ ATMOSPHERE CONTROL AND AIR TREATMENT
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List of References
[1] Why do we need to breathe oxygen? (1996, January 31). Retrieved November 26,
2015, from http://www.pa.msu.edu/sciencet/ask_st/013196.html
[2] Hypoxemia (low blood oxygen). (n.d.). Retrieved November 26, 2015, from
http://www.mayoclinic.org/symptoms/hypoxemia/basics/definition/sym-20050930
[3] Benson, B. B., & Krause Jr, D. (1984). The concentration and isotopic fractionation
of oxygen dissolved in freshwater and seawater in equilibrium with the atmosphere.
Limnology and oceanography, 29(3), 620-632.
[4] Ross, C. T. (2006). A conceptual design of an underwater vehicle. Ocean
Engineering, 33(16), 2087-2104
[5] Largest Dams, L. (2013, September 28). The largest submarine in the U.S. Navy
[Video file]. Retrieved from
https://www.youtube.com/watch?v=UxB11eAl-YE
[6] Massachusetts Institute of Technology. (September 12, 2001). Revision Paper about
Submarine Air Treatment. Retrieved from
http://web.mit.edu/12.000/www/m2005/a2/8/pdf1.pdf
[7] Herbich, J. B. (1998). Developments in Offshore Engineering: Wave Phenomena
and Offshore Topics: Wave Phenomena and Offshore Topics. Chapter 10, Diving
and Underwater Life Support. Gulf Professional Publishing.
[8] List of Ohio-class submarines. (2015, November 25). In Wikipedia, The Free
Encyclopedia. Retrieved 21:57, November 26, 2015, from
https://en.wikipedia.org/w/index.php?title=List_of_Ohio-
class_submarines&oldid=692455881

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[9] Powers, R. (n.d.). U.S. Navy Submarines Frequently Asked Questions. Retrieved
November 26, 2015, from http://usmilitary.about.com/od/navy/l/blsubfaq.htm
List of definitions, Symbols and Abbreviation
Alveoli: Alveoli are lungs sacs which allow oxygen and carbon dioxide to move between
the lungs and blood stream.
Hemoglobin: Hemoglobin is a protein molecule in red blood cells that carries oxygen
from the lungs to the body’s tissues and return carbon dioxide from the tissues back to
the lungs.
Cytochrome C: Cytochrome C is the electron transport chain in mitochondria.
Oxygen saturation: Oxygen saturation is the level of oxygen needed in a human blood
to be healthy
Hypoxemia: Hypoxemia is the abnormally low concentration of oxygen in the blood.
Vapor phase fugacity: Fugacity is the effective pressure which replaces the true
pressure in chemical calculations.
Corning model: Coring model Is a meter used to calculate the pH (Acid or Basic) of the
material
Ohio Class Submarine: is a class of nuclear-powered submarine currently used by the
US navy. It has 18 submarines.
Electrolysis: Electrolysis is a technique used to separate oxygen and hydrogen through
a direct electric current.
Microprocessor: The microprocessor is a computer processor that controls the
computer’s central processing unit (CPU)
𝑁𝑎𝐶𝑙𝑂3(𝑠): The S in the equation represents that it’s Solid

20. SUBMARINES’ ATMOSPHERE CONTROL AND AIR TREATMENT
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monoethanolamine: Monoethanolamine is also called Ethanolamine and it’s an organic
chemical compound.
aqueous: Aqueous solutions are solutions in which the water is the solvent.
SCUBA: Scuba diving is a mode of underwater diving where a diver uses a self-
contained underwater breathing apparatus to breathe underwater.