21-1. Habitability aboard a submarine is a measure of the adequacy of provisions for light, air, humidity, temperature, water, food, rest and recuperation facilities for the crew. In patrol reports submitted by our submarines during World War II, those conditions most frequently commented upon as adversely influencing habitability were: the deficiencies of ventilation and air conditioning while surfaced, submerged or running silent; poor breathing conditions incident to prolonged periods submerged due to accumulation of CO2, depletion of oxygen and increase of air pressure within the boat; the discomfort of cold, wet and rough weather while running surfaced; overcrowding; the inadequacies of water supply and sanitary facilities; the presence of certain noxious or toxic agents such as chlorine gas, carbon tetrachloride, oil fumes, and combustion products incident to fires; and material damage incident to enemy action or accidental flooding.
21-2. In a survey conducted by a representative of the Bureau of Medicine and Surgery of the reports of 1406 war patrols made by fleet type U.S. submarines during World War II, it was found that 658 war patrol reports contained no mention of habitability and conditions on those patrols are therefore presumed to have been fair or better, 106 reported "excellent" habitability, 408 reported "good" habitability, 171 reported "fair" habitability and 63 (4%) reported "poor" habitability. Of the 63 patrols reporting poor habitability, marked inefficiency resulted in only 23 of these due to unfavorable conditions and in only seven patrols was poor habitability in one form or another a deciding factor limiting patrol endurance. Five of these seven patrols were terminated due to contamination or shortage of fresh water and two were terminated due to prolonged conditions of high heat and humidity resulting from lack of air conditioning. Habitability conditions improved notably during the war as new submarines came into service and older submarines were modernized during overhaul periods. After 1942, the percentage of "excellent" reports received was doubled and the percentage of "fair" reports was considerably lowered. During 1943 and 1944 the percentage of reports of "poor" habitability was better than halved and remained at an all time low in 1945. However, the number of reports of only "fair" habitability at no period dropped to an insignificant level, indicating that much room for further improvement exists.
21-3. The program of installation of air conditioning equipment on U.S. submarines, which commenced in the Plunger Class in 1936, constituted a major improvement in the military utilization of our submarines for it made possible extended patrols in tropical waters. The principal benefits of air conditioning for submarine use are twofold: (a) the insulation life of electrical equipment can be greatly lengthened by a reduction in humidity, and casualties due to water condensation or dripping on exposed and energized electrical circuits can be avoided; (b) comfortable and healthful atmospheric conditions for ship's company can be maintained.
21-4. There is no more important measure of the habitability of a submarine operating under war conditions than the adequacy of its ventilation and air conditioning systems. Since the earliest installations, the cooling and dehumidifying capacity of air conditioning equipment as installed aboard submarines has been continuously improved keeping ahead of tremendous increases in crew carried and heat dissipating equipment installed. Frequent casualties during the war were experienced which temporarily disabled the air conditioning systems or, in a few instances, put the equipment out of commission for the major portions of patrols. It is to be noted, however, that U.S. submarines were not only the first to be air conditioned but at the end of the war, virtually the only ones with any significant air conditioning.
21-5. Unfortunately, under war conditions air conditioning and ventilation equipment could not be operated at all times. When conducting an attack approach or employing evasive tactics to escape enemy anti-submarine measures, U.S. submarine operational doctrine calls for the establishment of "silent running". In such circumstances, Commanding Officers usually followed the practice of securing inboard ventilation and air conditioning machinery to achieve minimum noise level, even though this equipment was sound-isolated on many submarines. Lack of air conditioning and ventilation while operating submerged in tropical or semi-tropical waters has almost invariably resulted in high humidity and excessive heat conditions within a very short period of time. Numerous patrol reports have stressed the deleterious effects on personnel of extended periods of silent running and in a few cases the military efficiency of our submarine crews was reported to have been seriously reduced during critical periods. For example, Plunger (SS179), while submerged and in contact with the enemy on 1 March 1943 near Makin Island, reported "Noisy air conditioning equipment was shut down as we went in across the bow of the escort. Temperature in the maneuvering room was 130°F. and the engine rooms were about the same . . . men in these two compartments were near prostration from the heat; one man was already receiving treatment. The men on the wheels and planes were being rotated every 5-10 minutes by which time they were totally exhausted . . . Response was slow and acuity dull. Errors were prevalent. It was evident that the ship no longer was in condition to fight or defend itself". Plunger thereupon broke off the action without attacking.
21-6. As an example of difficulties encountered when without the benefit of air conditioning during even normal submerged operations, the following excerpt are quoted from
(SS198) second and third patrol reports. "Due to faulty air conditioning units (leaks in Freon piping) the boat was oppressively hot and humid and there was a strong tendency for electrical grounds and short circuits to develop and for finely adjusted contraptions and mechanisms to become inoperative through corrosion. After two weeks of all day submergence all the bunks were wet and stinking. Clothing in the lockers in the forward and after torpedo rooms was green with mildew; practically everyone had a heat rash. There were two cases of heat exhaustion. . . . 30% of the crew developed some type of fungus infection . . . men and some of the officers resorted to sleeping in the torpedo room bilges where it was not quite so hot . . . Lack of air conditioning decidedly had a debilitating effect on the crew and slowed their reactions".
21-7. During prolonged periods of submergence, further deterioration of the atmosphere has generally been experienced due to excessive accumulation of CO2 and depletion of oxygen. The physiological effects of prolonged exposure to such conditions are well known to submarine personnel. To revitalize depleted air, oxygen replenishment with or without the use of compressed air was commonly employed in conjunction with removal of CO2 by use of chemical absorbents. Foul air together with high humidity and extreme heat due to lack of air conditioning have in several cases seriously reduced the efficiency of our submarine crews. For example, enemy action forced Puffer (SS268) to remain submerged for 38 hours during her first patrol, the longest known dive made by a U.S. submarine during the war. It was reported that "at the end of 38 hours submerged the men were breathing heavily and almost completely exhausted in spite of all available means being used to purify the air . . . With the air conditioning shut down, the temperature within the boat went to a high figure. A temperature of 125°F. was reported in the maneuvering room. All of the men were nauseated and 75% were vomiting. Both CO2 absorbent and oxygen were used but despite that, the air was very foul towards the end. . . . Headaches were severe. A good many men were in a state of physical collapse . . . towards the end, stations were manned by volunteers who had the stamina and will to move and think. Many of the others were past the stage of caring what happened". In Puffer's case, as in many others, it is impossible to differentiate between the relative deleterious physiological effects of increased CO2, depleted oxygen, increased air pressure, and high humidity and extreme heat caused by lack of air conditioning. Any one of these causes acting alone is sufficient to cause discomfort.
21-8. Before submerging, whenever circumstances permitted, most Commanding Officers followed the practice of thoroughly ventilating their submarines so that the air within at the onset of the dive would be as pure and fresh as possible. In extreme cases, such as Puffer's prolonged dive, the condition of the ship's atmosphere at the time of diving may be a major factor in determining the maximum possible time of submergence. According to Chapter 38, Bureau of Ships Manual, the established limiting concentrations for minimum safe breathing condition of 17 per cent oxygen and 3 per cent CO2 will not be reached, assuming fresh air to start with, until the expiration of a period of hours calculated by the following formula: T = 0.04V/N, where T is the number of hours, V is the volumetric content of the submarine in cubic feet and N is the total number of men in the crew. By this formula, the limiting values for SS212 and SS285 Class submarines should be reached in about 18 hours. If time spent submerged under ordinary operating conditions is less than the period listed above, oxygen or compressed air replenishment and carbon dioxide purification should normally not be necessary. However, if it is predicted that the time of submergence will be greater than the limiting period, then air purification with CO2 absorbent should be resorted to when the CO2 concentration reaches 2% and oxygen replenishment should be undertaken at the end of the period.
21-9. Study of some 89 cases of prolonged submergence where foul atmosphere was commented upon and recorded values of the CO2 and oxygen content of the air were reported, indicates that the limiting period of time allowed by the above formula is not always applicable to wartime operations. In 22 of the above reports, the actual limit of viability of the air was from one to six hours less than the calculated figure Early use of CO2 absorbent should certainly be resorted to whenever long dives can be anticipated. It should be noted that a given weight of the CO2 chemical absorbent will always absorb a given amount of CO2 and that no absorbent can be saved by waiting for high CO2 concentrations.
21-10. An additional factor which often has affected the habitability of submarines operating under war conditions is the increase of internal air pressure usually experienced during prolonged dives due to the cumulative effect of small air system leaks, venting of tanks inboard and firing of torpedoes. Increases in barometric pressure as high as 12 inches (Hg) from these sources were reported in several cases. When not in contact with the enemy, the common practice during the course of a long dive, and often in conjunction with the revitalization of the air supply and use of CO2 absorbent, was to reduce the excessive pressure by pumping air from thee ship's atmosphere into the air flasks with the high pressure air compressors. A much more effective measure, however, is to operate the low pressure blower, discharging the air into one or more ballast tanks and thence overboard through the ballast tank vents. Increase in air pressure can be annoying not only from the standpoint of headaches and decreased efficiency induced by the higher than normal pressure alone, but also because some members of the crew may not be able to equalize this pressure within their middle ears and will suffer consequent sharp pain and decreased hearing ability. In addition, increased air pressure will tend to accelerate the poisoning effects of CO2 and whatever other toxic gases may be present.1
21-11. In several cases, toxic or noxious gases have been released in our submarines as a direct or indirect result of war damage. When operating submerged, the military efficiency and even the survival of a submarine can easily be affected by the contamination of the atmosphere with objectionable or deadly gases since these, if present, cannot be ejected. Fires have been the principal source of such gases.2 Chlorine gas formation has been reported in several instances following the introduction of salt water into torpedo batteries or main propulsion batteries. Hammerhead (SS364) on her fourth patrol reported "Battery compartment of torpedo flooded during attack, emitting chlorine gas into boat". Peto (SS265), while submerged and undergoing depth charge attack on her first patrol, detected chlorine gas in the after battery compartment. It was discovered that salt water had been introduced into the main battery from a leaking engine air induction drain and battery ventilation drain which were interconnected. Fortunately, only five cells received a small quantity of salt water and release of chlorine was slight. On Grenadier's (SS210) fourth patrol,
as the result of a depth charge attack, salt water leaked into the after battery sump from a watercloset that overflowed due to its sea valves jarring open. Sufficient chlorine gas was released from contact of this salt water with the battery acid accumulation in the sump to cause acute discomfort to all hands. Symptoms were aching joints, headaches, pains in throat and lungs, rasping cough, and some cases of vomiting. The efficiency of the whole ship's company was adversely affected for several days. Grenadier's experience demonstrates the desirability of routine periodic flushing of battery sumps with fresh water and soda lime solution to prevent accumulation of acid. On S-27 and S-36, both of which went aground and were abandoned, salt water entered the battery compartments and chlorine gas was generated.
21-12. In a few instances fumes from fuel oil leaking into the hull through inboard vents or leaking compensating and transfer lines have caused minor discomfort. For example, Tunny (SS277), heavily damaged on her seventh patrol, reported "All hands had headaches from breathing oil fumes from the oil leaking into the boat from the No. 7 normal fuel oil tank".
21-13. The type of refrigerant used in air conditioning and refrigerating systems is a matter of much importance on submarines since, on several occasions, depth charge attacks have caused release of refrigerant gas through damaged joints and fittings. Freon 12 is currently employed for air conditioning and refrigerating purposes on U.S. submarines and is ideally suited for such use since it is non-inflammable, non-explosive, odorless and no-toxic in quantities up to 20 per cent by volume. No ill effects were reported in those instances where Freon escaped. An interesting example of what can happen through the use of less suitable refrigerants is the experience of the Dutch submarine HNMS O-19. O-19 was heavily depth charged on the night of 9 January 1945, while operating under the command of ComSubsSoWesPac during her third war patrol, and was forced to the bottom by the first attack. While still on the bottom, another close depth charge attack was received, one of the most serious effects of which was to cause CO2 to leak from the engine room air conditioning system. The stern compartment and the engine room were immediately evacuated but in spite of closing all bulkhead watertight doors, CO2 reached the control room and made it necessary for personnel to evacuate to the conning tower, the CO2 being heavier than air. The pressure in the boat rose steadily due to internal air leakage from various air systems and accelerated the physiological effect of the CO2 on personnel. Escape breathing equipment (Draeger), fitted with soda lime containers, was used to absorb excessive CO2 content in areas of dangerous concentration. The telephones were out of action and personnel in the various compartments had no way of ascertaining what was going on in the other spaces. Two hours later, the boat was surfaced with the engine room still secured but was immediately placed on the bottom again when two enemy vessels were sighted close aboard. It was then decided to re-enter the engine room while submerged, ready the engines and then attempt to escape at high speed on the surface. A small party of men using rescue breathing equipment (DESA) managed to enter the engine room and rig the engines for immediate starting. The engine room was found half flooded, the leakage
occurring through sea valves which had jarred open during the last depth charge attack. Some men who removed their DSEA sets in order to reach valves located in confined areas were overcome by the CO2. All of the men in this party suffered after effects to some extent from CO2 poisoning. The ship was then surfaced and escaped without difficulty, the enemy having departed. Repairs were undertaken at Fremantle, W.A., at which time the air conditioning plant was converted for use with Freon gas.
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1. See paragraph 22-15 and Tang narrative, paragraph 10-25.
2. See Grenadier narrative, Section VIII, and Scamp narrative, Section IX, for illustrations of the effect of combustion products from fires on personnel and ship operation.