SUBMARINE AIR TREATMENT Revision September 12 2001 Learning Objectives 1 Describe how oxygen is produced on submarines with the following processes electrochemical oxygen generator and oxygen candle furnace 2 Describe how carbon monoxide is removed from the submarine atmosphere with the following processes LiOH absorbers and CO H2 burner 3 Describe how carbon dioxide is removed from the submarine atmosphere using the CO2 scrubber 4 Describe how H2 is removed from the submarine atmosphere using the CO H2 burner 5 Discuss the impact of submarine atmospheric pressure changes with respect to the following biologically essential and or sensitive gases oxygen carbon monoxide and carbon dioxide 6 Describe the use of activated carbon for the removal of odors and other noxious gases 1 of 16 Table of Contents 0 1 2 3 4 5 6 7 8 9 Life in a Confined Space in a Hostile Environment Submarine Atmosphere Characteristics Medical Toxicological Considerations Physiological Problems Classification of Materials by Biological Effect Atmosphere Control Systems 5 1 Oxygen Supply Systems 5 1 1 Electrochemical Oxygen Generator 5 1 2 Solid Polymer Oxygen Generator 5 1 3 Oxygen Candle Furnace 5 2 Carbon Dioxide Removal 5 2 1 LiOH Absorbers 5 2 2 CO2 Scrubbers 5 3 Air Purification 5 3 1 CO H2 Burners 5 3 2 Activated Carbon Emergency Air 6 1 EAB Emergency Air Breathing 6 2 OBA Oxygen Breathing Apparatus 6 3 SCBA Scott Air Packs Atmospheric Monitoring Conclusion References 2 of 16 Life in a Confined Space in a Hostile Environment A story to set the stage 1 Welcome to my l atmosphere diving bell We will be making a hypothetical observation dive to 300 feet 91 4 m beneath the ocean s surface to survey the wreckage of the Andrea Doria You will notice that this capsule although only eight feet 2 4 m in diameter contains most of the comforts of home The atmosphere inside this capsule is indistinguishable from the air we breathe on the surface thanks to an environmental control system which continually monitors and adjusts the temperature and humidity We have just reached our destination when for some unexplained reason we suffer a complete shutdown of our main power supply and primary life support systems It appears that we have become entangled in some type of obstacle on the bottom and severed our power cable which connects us to the surface Please don t panic Auxiliary battery power is presently supplying eerie low intensity lighting in our sealed compartment The se batteries should last for at least 48 hours It is at least some consolation to know that our capsule has inch 1 3 cm thick walls and is constructed of high yield strength steel The bell will keep us from being crushed by the outside pressures which are over 10 times those inside thumb rule pressure increases 1 atmosphere for every 33 feet of depth in seawater Our initial concern is to our supply of oxygen Presently our bodies are consuming approximately 0 3 0 5 liters per minute of oxygen gas to support our resting metabolic functions This oxygen is being taken from the capsule atmosphere If not replenished the oxygen content in this atmosphere will slowly decrease from its initial value of approximately 21 by volume If the oxyge n content is allowed to drop to 16 we will begin experiencing labored breathing confusion and finally unconsciousness Even if we can t replenish this atmosphere with fresh oxygen at the rate at which we are consuming oxygen we should have nearly 6 hours before these symptoms become noticeable and up to 13 hours before we are unconscious We fortunately brought along an additional supply of oxygen to extend these times by 12 hours But by all means please stay calm as increased anxiety will only increase our oxygen consumption rates Even of more concern is the buildup of carbon dioxide which our environmental sensors are detecting Since we no longer have power to operate the ventilation fans in our capsule the air from our atmosphere is no longer being forced through the carbon dioxide absorption system which we have on board The carbon dioxide which our bodies are generating through normal metabolism is being dumped into our capsule environment As in the case of oxygen our bodies are tolerant of only a slight variation in the carbon dioxide content in the air which we breathe Even though we can tolerate short exposures at carbon dioxide levels of up to 3 4 we will begin experiencing respiratory discomfort a feeling of air hunger and perhaps dizziness and nausea when breathing only 1 2 carbon dioxide for extended durations at 6 we will be on the brink of unconscious Based on our present rates of carbon dioxide generation our capsule environment is predicted to reach 2 levels 1 Nuckols et al 1996 3 of 16 of CO2 in approximately 3 hours and 6 in slightly over 6 hours Don t be surprised though if you experience a headache and reduced sensory perceptions hearing seeing etc before these times are reached Again steady yourself further anxiety will only speed up the timetable You say that it is getting cold Unfortunately the capsule is not insulated Without the electrical heating system which was more than adequate when power was available the temperature inside the capsule quickly reaches the surrounding water temperature of about 40 F 4 4 C We need to try to stay as warm as possible since any shivering will only increase our oxygen consumption and carbon dioxide generation rates One way that we can re warm the cabin atmosphere and ward off the extremely uncomfortable consequences of being cold is to pressurize the bell with our emergency gas banks By increasing the cabin pressure we immediately feel a renewed warmth not unlike the rise in temperature that we see when inflating an automobile tire If done in stages we may have a chance to offset the continual heat loss from the bell to the surrounding water and maintain a tolerable cabin temperature until rescue is made But alas the increase in cabin pressure offers only momentary relief from the extreme cold The lack of insulation and immense heat sink provided by the ocean quickly dissipates the increased temperature to that of the ambient water temperature In addition the increased cabin pressure has caused even further problems The physiological responses of our bodies to the levels of carbon dioxide in the cabin are increased proportionately to increases in pressure An environment at 10 atmospheres of pressure having only 0 5 carbon dioxide will be as toxic to our bodies as
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