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PART 2

SUBMARINE MEDICINE PRACTICE



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CHAPTER 18
SUBMARINE HABITABILITY AND CLOTHING

CONTENTS

    Page
18.1. HABITABILITY IN SUBMARINES 266
  18.1.1. General considerations 266
  18.1.2. Background 266
  18.1.3. Definition 267
  18.1.4. Factors of habitability 267
18.2. HABITABLE SPACE 267
18.3. THE ATMOSPHERE 268
  18.3.1. Volume 268
  18.3.2. Pressure 268
  18.3.3. Oxygen and carbon dioxide 269
  18.3.4. Atmospheric contaminants 270
  18.3.5. Battery gases 271
  18.3.6. Engine exhaust fumes 271
  18.3.7. Oil vapors 271
  18.3.8. Other impurities 271
  18.3.9. Odors 272
  18.3.10. Bacteria 272
18.4. THERMAL HABITABILITY 272
  18.4.1. Air-conditioning system 272
  18.4.2. Effective temperature 274
  18.4.3. Extremes of temperature 274
18.5. DESIGN OF COMPARTMENTS 275
  18.5.1. Lighting and color 276
  18.5.2. Working areas 277
  18.5.3. Recreation areas 277
  18.5.4. Sleeping spaces 278
18.6. NOISE 278
18.7. OTHER HABITABILITY FACTORS 279
  18.7.1. Food and nutrition 279
  18.7.2. Fresh water 279
  18.7.3. Sanitation 280
  18.7.4. Ship's motion 280
  18.7.5. Safety 280
18.8 SUBMARINE CLOTHING 280

408832 O-57-18


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CHAPTER 18
SUBMARINE HABITABILITY AND CLOTHING

18.1. HABITABILITY IN SUBMARINES
 

18.1.1. General considerations.

The submarine is primarily a vehicle for the concealed transport and accurate delivery of torpedoes and other weapons. She also serves as a domicile for a specialized complement of sailors who must adapt themselves to stresses peculiar to undersea warfare. Within her compact environs, crowded as they are with endless items of material, there must remain some cubic footage to be allotted for the duty stations, messing, berthing, and varied activities of her crew.

Virtually every single technological advance in modern naval vessels has represented a corresponding attrition in space or comfort to personnel. Larger propulsion plants demand more fuel, stored in larger tanks; complex electronic and hydraulic units require more men to be stationed aboard for operation and maintenance; and more cooks and administrative rates are necessary in proportion to any increase in complement.

It was demonstrated in World War II that a considerable degree of inconvenience and discomfort can be endured by strongly motivated submariners who possess the stamina required to do reliable work under adversity. But infringement upon the fundamental organic and psychic personal needs of man cannot increase indefinitely without encountering a point of diminishing return in human performance. The relentless influx of space occupying, heat generating, and noise making equipment aboard ship can invade and usurp habitable room between unyielding bulkheads until that critical level is reached beyond which the ship's operational efficiency is jeopardized.

It is axiomatic that the fighting effectiveness of any ship is the product, not the sum, of its integral components. Not the least of these components is its personnel, for without teamwork and spirit

  even the most advanced equipment is negated. A poor standard of habitability is a poor installation of personnel, equivalent to faulty installation of engines or torpedo tubes.

18.1.2. Background.

Early efforts at making life more tolerable for the seafaring man were met by derision even by the old salts themselves, who accepted the ways of the sea as arduous and who regaled the land-lubber with chanteys and staunch sagas of hardship and endurance. Poor ventilation, scurvy, bully beef and hard tack were only a part of his test of mettle. Usually he was unaccustomed to conveniences, having come from the hardy frontier life of his day. Since the Industrial Revolution, however, the sailor has had to make a greater adjustment to shipboard life, as he represents a people who have come to take for granted modern conveniences and creature comforts as a part of their national life.

As long ago as 1891, a naval officer essayist wrote, "There are positive faults in the internal arrangements of our newer ships which will neutralize the allurement of any pay table * * * and in the end drive out of the service the very class of men and boys that we are now so earnestly endeavoring to attract into it. The more modern the ship and the greater the need for intelligence in her crew, the more objectionable she seems to become in point of quarters for the men, until we have about reached the point where it is well to call a halt on certain disastrous tendencies in the direction of the utter disregard of what intelligent men are capable of putting up with." And as recently as 1891, a senior officer in discussing this essay remarked: "Although believing in all comforts possible for the men, it is thought that the essayist places too much stress upon them The old saying might be slightly changed to read, 'He who goes to sea for comfort ought to go to _ _ _ _ _


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for pastime'; given good pay and prospects for advancement, and young men will cheerfully give up comfort."

18.1.3. Definition.

Webster's Unabridged Dictionary defines habitability as the capability of being inhabited or dwelt in; specifically of a dwelling, reasonably fit for occupation by a tenant of the class ordinarily occupying such a dwelling.

This is a word with an abstract definition which has assumed diverse meanings, having been incorporated into various professional and industrial jargons. Improvement in habitability is the direct concern of countless sciences, trades, arts, and industries, each branch of which appends its own specialized concepts until the term has become almost nebulous. The wide variety in design of homes reflects the several opinions of builders and architects regarding styling, arrangement, and standards of livability of dwellings. The problem is vastly multiplied when it comes to the manufacture of a submarine, one of the most complex environmental structures which man has ever been called upon to occupy.

To its inhabitants, a submarine is a steel capsule which encloses them as they venture into a completely artificial environment beneath the surface of the ocean. Only by taking along the "external milieu" to which mankind is adapted, encased in a pressure-proof hull, is it possible for man to exist indefinitely in the "internal milieu" of his phylogenetic prototypes.

  Because of the development of radar and sonar and the improvement of antisubmarine weapons in recent years, submergence times became increasingly prolonged. The fleet submarine has evolved through the snorkel and guppy stages, with manifold intensification of stress upon the crew. The ultimate in this trend is a true submersible, capable of avoiding detection for weeks or months without surfacing. This is the goal of the project officers of the nuclear powered submarine. Among the crucial determinants of how true a submersible she will be is this question: Can she make sufficient allowance for the limitations of her crew?

Much can be done toward decreasing the limitations of the submarine crew by assessing the men as they apply for duty in submarines, selecting in advance those who manifest the least likelihood of maladjustment. As a complementary consideration, it is essential that a crew so chosen should not be subjected to unnecessary environmental strain. Good habitability must be attained and maintained by a continuous organized program of appraisal and revision in design of submarines-those which are active in the fleet, as well as those still on the drawing boards.

18.1.4. Factors of habitability.

The salient facets of habitability are mentioned insofar as they pertain to submarines. A recommended list of references is appended for detail which cannot be covered here.

 
18.2. HABITABLE SPACE
 
Space is at a premium in any type vessel; particularly is it critical in submarines, which are noted for their compactness. Overcrowding causes a lack of "elbow room"; decreased freedom in moving about the boat; absence of privacy; limited availability of head and shower facilities, bunking room and personal stowage room. Deprivation of these factors gives a man a sense of futility in commonplace activities which may be reflected in his performance of duty. Usually there is just no place to go except to his bunk when he leaves his watch station. He becomes aware of the mannerisms of others, and becomes irritated at the nervous habits of himself and his shipmates. Paucity of space accentuates the friction which arises after everyone has run out of jokes and sea stories.   Nowhere has there been more effort in making the most efficient use of space than in the submarine. Dual use is made of space wherever possible by such ingenious devices as bench lockers, folding or convertible tables, overhead lockers and brackets, and hinged lavatory basins. The commissary department must be especially inventive in putting away provisions for a long cruise, often campaigning and bargaining for cubic feet which have been contested by other departments. More than one ship has eaten salty potatoes which have been stowed in the superstructure.

A logical way to provide additional space would be to build larger submarines. This would make the ship less maneuverable and more vulnerable unless accompanied by an extra round of


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propulsion equipment, personnel, etc., which again revive the vicious spiral.

Large quantities of space are occupied by equipment which has been placed aboard in an attempt to improve comfort for the crew. The ventilation and air-conditioning systems in particular are examples; also the washing machine, ice cream freezer, recreational gear, electric heaters, and walk-in chill boxes. Strange to say, it is felt by many submariners that the value obtained from even some of these items does not repay the sacrifice in space. The ice cream freezer iv. not used in cold climes during peacetime, nor is the commercial model washing machine when frequent port calls are made.

It is a problem to curtail the accumulation on board of unnecessary equipment, back issues of logs and publications, and excessive inventories of spare parts and provisions. With the current specialization of submarines into types (SSK, -R, -P, -O, -N), there may be a tendency for required allowance lists to become all-inclusive, containing items which are essential aboard some types, but only supernumerary or unnecessary aboard others. This decrement in space can be compensated in part by designers, but there is no substitute for periodic and rigorous paring down of excessive onboard material.

Efforts have been made to miniaturize equipment, and the aircraft electronics field reports the saving of space by "miniaturizing miniatures." To simplify a number of installations without loss of their function, e. g., eliminate experimental features upon adoption of production marks and models, would render some of the maintenance

  men dispensable. Automatic devices have tended often to reduce the number of operating personnel, but at times this advantage has been lost by an increase in maintenance men required. Increased durability of equipment would permit its upkeep during availability periods by shore-based personnel, with fewer breakdowns at sea for ship's force to remedy.

Reduction in number of equipment operators can be effected by human engineering improvements; design of controls, dials, manifolds, panels, and switchboards, with better lighting, readability, and convenience of handling. If one watchstander thereby can do proficiently the work of two, it is possible that the three crewmen standing watch on the second piece of gear can be eliminated from the crew, leaving more habitable space per man. A notable example of this is seen in the new diving station arrangement aboard submarines, whereby one man can serve simultaneously as helmsman, bow planesman, and stern planesman.

The end results of most of these efforts are to have fewer billets and more habitable space within the same floodable volume. Leaving operators and maintenance personnel ashore lessens the demands for provisions and fresh water; there is less requirement for feeding (fewer cooks needed), for administrative supervision, and for medical care. There is more generous apportionment of head, shower, and recreational facilities; more cold storage room per man for frozen foods and meats; higher permissible standards of sanitation and hygiene; more personal locker space; and more room to walk around in.

 
18.3. THE ATMOSPHERE
 
18.3.1. Volume.

The amount of air contained in a submarine is about equal to the floodable volume and proportional to the barometric pressure. It is circulated throughout the ship by centrally located supply and exhaust blowers of large capacity, usually found in the forward engine room. Supply suction can be taken from outside the ship through the main induction line while on the surface, at which time the inflow of air is supplemented by the powerful suction of the diesel engine scavenger blowers. An outside source of air for ventilation is also available to snorkel-equipped submarines when the -mast induction is rigged at snorkel depth.

  Otherwise during submergence the air inside the ship is recirculated by setting the blower loeuvers so that the exhaust blower discharges into the supply blower intake. This affords a diffusion of the air, the oxygen tension dropping and the carbon dioxide tension rising fairly uniformly in all compartments. Vitiating components are disseminated and diluted in the same fashion, their localized concentration rising relatively slower than if there were no recirculation.

18.3.2. Pressure.

Contrary to popular belief among the laity, there is not much fluctuation of pressure inside the submarine. The barometric reading varies an


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inch or two at most in the routinely operating fleet type submarine. Extensive use of the torpedo tubes as while laying mines causes somewhat higher pressure which can be returned to normal by using the air compressors in the pump room to return the excess air to the high pressure storage banks.

There is sudden but not drastic fluctuation of air pressure during snorkeling. If the top of the snorkel mast should dip beneath the water's surface, e. g. because of high waves in rough seaway or loss of depth control, there is automatic closure of the head valve to prevent flooding of the snorkel and a quick vacuum is drawn in the boat by the diesel engine intake. The head valve will again open when it clears the surface with a sudden equalization of pressure with the outside. A low pressure trip will shut down the engines automatically if they should pull a vacuum equivalent to an aircraft altimeter reading of 6,500-7,000 feet above sea level.

Rapid opening and closing (cycling) of the snorkel head valve with prolonged intermittent pressure changes can be annoying to the crew, especially during sleep hours. Resulting incidence of aero-otitis media and sinusitis is high when there is prevalence of respiratory infections; these may be controlled by mucous membrane shrinking agents and antihistamines. Isolated instances of recurrent ear pain may be due to exuberant lymphoid tissue at the Eustachian tube ostia often relieved by radium treatments after diagnosis by nasopharyngoscope.

Early snorkel exercises in 1947 were begun with misgivings about these E. N. T. and psychological complications, but it was soon found that crews were very adaptable to continuous snorkeling on prolonged cruises exceeding 30 days and for distances approaching 6,000 miles.

18.3.3. Oxygen and carbon dioxide.

Once the submarine is sealed, the point at which clinical asphyxia would be reached is determined by three variables: (a) the number of people aboard; (b) the floodable volume of the ship, and (c) the rate of gaseous metabolism per person, taking into account heavy work and amount of smoking. A formula containing these variables is employed to determine the time at which there should be revitalization, or artificial addition of oxygen and removal of carbon dioxide, as an

  alternative to obtaining ventilation from surface air:

X=0.04(C/N)

Where:

X=number of hours after thorough ventilation until the oxygen concentration is expected to be about 17 percent, CO2 about 3 percent.

C=floodable volume of the ship; this is about 35,000 cubic feet in the fleet type hull.

N=number of men aboard.

If submerged time of over 24 hours is anticipated, CO2 absorption should be begun soon after diving, with replenishment of oxygen at the time designated by the formula.

Aviators' oxygen is carried in commercial containers in each compartment, from which a measured volume of oxygen can be released into the boat when indicated by the revitalization formula.

Carbon dioxide absorbent is stowed in canisters of thin metal in all compartments. Each canister contains about 15 pounds of lithium hydroxide which should be spread on a flat surface such as a mattress cover, and stirred at intervals to promote absorption. The hands should not be used for stirring because of the heat generated in the chemical absorption, and the stirring should be gentle to avoid scattering caustic dust. The chemical is deliquescent, losing its activity when it becomes moist. The cans of absorbent are weighed periodically; a weight gain indicates water absorption and loss in chemical effectiveness of the agent.

The air can also be freshened by bleeding fresh compressed air from the banks into the boat ; this increases oxygen tension and dilutes the carbon dioxide without reducing its tension.

The onset of asphyxia is very insidious because it is so gradual under these circumstances. When a fleet submarine has been submerged over about 16 hours, depending on the variables mentioned above, a cigarette will go out quickly if set aside, and a match will go out as soon as its head has burned. About this time several of the crew begin to complain of headaches; someone notices that everyone is breathing rapidly and deeply; and the manifestations of irritability and impaired judgment become evident. These premonitory signs correspond roughly to about 3 percent concentration of carbon dioxide. The natural feeling


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of one who does not realize the gravity of these signs is, "We'd better save the soda lime for the next time, when things might be a lot worse." By this time revitalization is already overdue.

A Dwyer chemical carbon dioxide analyzer, figure 129, is found on each submarine, for determination of the gas in percent. Beckman oxygen meters are useful and accurate, but are not carried aboard usually because of their sensitivity to damage and loss of calibration.

Future plans for air regeneration methods include the use of chemical carbon dioxide "scrubbers" which can be activated by automatic monitor circuits to maintain carbon dioxide at the tension desired, and large banks of oxygen with manifolds and electronically controlled solenoid valves for release of oxygen into the living spaces as required. It is at least theoretically possible

  to manufacture oxygen from sea water. All of these projects will be limited by their weight, complexity, and the space they utilize.

18.3.4. Atmospheric contaminants.

Objectionable and harmful contaminants of the atmosphere inside the submarine accumulate from many sources during long submergence. Whereas the brief diving times of earlier submarines were not usually long enough for the building up of toxic levels, the prospect of a true submersible in the immediate future poses the reappraisal of gases which have not been even thought of before as being toxic. Industrial medicine authorities have set standards for exposure to toxic gases and vapors in factories, in terms of "maximum allowable concentration" (m. a. c.) for intervals up to a full 8-hour working day. No one, however, has previously considered

Photo of crew in control room using Dwyer analyzer.
Figure 129.-Analyzing the submarine atmosphere for carbon dioxide by the Dwyer analyzer.

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the possibility of people being exposed to these materials for weeks and months without interruption.

18.3.5. Battery gases.

Very large lead storage batteries are depended upon for underwater propulsion ; the cells discharge at variable rates as the ship is driven through the water at different speeds, and are recharged by diesel driven generators. Water from the electrolyte is hydrolyzed at the poles, in large amounts if there is a rapid rate of charge or discharge, and/or a high cell temperature. Rapidly evolved gases then bubble to the surface, and the cell is said to be "gassing." Each of the battery wells is continuously ventilated by its own set of exhaust blowers, to forestall the buildup of high concentrations of these gases at any point in the ship. Hydrogen, which evolves from the cathode plates, is highly explosive at or above the 4 percent level. It is physiologically innocuous.

Antimony is added to the lead sulfate of the cathode plates to improve their durability and length of life. Hydrogenation of antimony during gassing produces stibine (SbH3), an explosive gas with a characteristic unpleasant odor, which dissociates rapidly at room temperature, and which acts toxicologically as a lower respiratory irritant and a hemolytic agent, with traces of antimony excreted in the urine. An impurity in lead storage battery plates is arsenic, which forms arsine (AsH3) upon contact with nascent hydrogen; this gas is more stable than stibine, has a garlic-like odor and, after a delay of a day or two after exposure, causes such symptoms as malaise, dyspnea, headache, fainting, nausea and vomiting, dark urine, anemia, and jaundice. Arsine is spoken of as a "blood and nerve poison." Neither gas has been positively incriminated in the present day submarine.

Pollution of battery electrolyte by sea water produces chlorine gas in large amounts, the effects of which are well known in chemical warfare. Chlorine is absorbed by soda lime, which is the active agent in the ship's SEA's (Submarine Escape Appliance-currently the Momsen lung) ; scrubbers should also remove chlorine from the atmosphere. The battery well is sealed off when chlorine is detected.

18.3.6. Engine exhaust fumes.

Leaky exhaust manifolds or fittings, cracked

  cylinder liners, intake of exhaust fumes through the snorkel induction while cruising downwind, or excessive back pressures in the snorkel predispose the collection in the submarine atmosphere of irritation gases which are products of combustion in the diesel engines. These are oxides of sulfur, hydrogen sulfide, methane, ozone, and most deadly and insidious of all, carbon monoxide. It is said that the latter will not be found in great quantity in the absence of the typical exhaust gas odor; unless, of course, the CO has come from some other source.

18.3.7. Oil vapors.

Hydraulic oil leaks from high pressure lines form an atomized spray or "toxic mist" of saturated hydrocarbons, glycols, higher alcohols, and butyl cellusolve, causing eye irritation, respiratory irritation, headache, dizziness, and nausea. Another danger of some of these mists is their explosibility. Fuel oil or grease evaporating from hot surfaces such as engines or ranges add a nauseating odor. Oil films collecting on the skin promote dermatitides venenata, and chronic aspiration of oil vapors may conceivably result in lipoid pneumonia, especially if the ciliary activity or the cough reflex is depressed by other agents. In order of increasing carbon chain length, the gaseous hydrocarbons are asphyxiants and strong anesthetics, and the long chain liquid hydrocarbons are primarily skin and respiratory irritants.

18.3.8. Other impurities.

Mercury vapor, from gyrocompasses, clinical thermometers, and especially from mercury vapor bulbs which are broken while hot, reaches m. a. c. in infinitesimal amounts. Freon-12, leaking from the refrigeration and air-conditioning units, is not an inert gas as was commonly supposed. It is an anesthetic gas; also when oxidized by flame, as when a halide torch is used to detect freon leaks, deadly phosgene gas is formed. Acrolein, one of the most toxic gases known, is given off by hot cooking grease and fats, also from electrical insulation as it ages. Ether, if stored in cans in the medical locker, is hazardous if the cans are ruptured or left open.

Another source of carbon dioxide is from the use of the fire extinguishers. Carbon monoxide is also liberated from aging phenolic paint and varnish compounds, and from smoking of tobacco. Both these gases are given off with caustic smoke and


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acrid phenolic fumes if an uncontrolled fire occurs inside the ship.

Many persons are hypersensitive to tobacco smoke if exposed for long periods, especially if not accustomed to smoking. Radiation decomposition products from luminous dials and radon plaques have only recently been found to be a definite health hazard.

18.3.9. Odors.

The principal cause of objectionable odors has been due to the design of heads and sanitary tanks, which does not feature a water trap or other seal to prevent "pervasion of the ship with an aroma resembling in no way the attar of roses." Defective flapper valves permit flies to breed in warm climes and to enter and leave the sanitary tanks freely. In order to empty a sanitary tank to sea, as is done about twice a day routinely, all drains into the tank are closed, an air pressure is built up, and the contents of the tank blown overboard through a discharge line. The tank must now be

  vented, either outboard when on the surface, or inboard when submerged. An activated charcoal air filter is in the inboard vent line, which removes much of the odor when the venting is done slowly and when the filter unit is replaced often.

Other odors come from fuel oil, chemical agents, tobacco smoke, cooking, and those emanating from human bodies. Man has an ability to detect the presence of odors which is much more acute than any chemical or physical means known. There is no clear definition of the physiologic effects of disagreeable odors, except that there is a definite reduction in appetite and a disinclination to physical exertion.

18.3.10. Bacteria.

Pathogenic microorganisms may live briefly in the atmosphere, and conduction of communicable disease in the form of droplet infection is a real problem in the recirculated air of sealed submarines. Air sterilization methods have not been perfected.

 
18.4. THERMAL HABITABILITY
 
Man is a homeothermic animal; i.e., he maintains his own internal milieu at a constant temperature by regulatory centers in the central nervous system, located chiefly in the anterior and posterior hypothalamus. These centers exert their control in heat balance through the autonomic nervous system, with regulated dissipation of heat from the metabolic processes in the muscles and viscera. There is a relatively constant loss of heat through the lungs and a fairly fixed amount of heat loss in the excreta; the skin is the primary factor in the regulation of body heat.

Some heat transfer to the outside occurs by radiation; a little by conduction to garments and to cooler surfaces with which the body may come into contact; a larger amount by evaporation of sweat, with a giving up of latent heat of vaporization as this aqueous material evaporates; but mostly heat is transferred by the process of convection, as steady movement of air over the skin replaces the warm layers next to the skin with cooler air.

If the relative humidity of the air is low, as evidenced by a wide difference in dry and wet bulb thermometer readings, the amount of water vapor which it is carrying is well below saturation, and

  the process of vaporization becomes more significant because evaporation from the skin surface is promoted. This is the end accomplishment of the air-conditioning units which have been used with such great success in submarines.

18.4.1. Air-conditioning system.

Large refrigerant coils are placed in the main ventilation supply conduits in submarines, with freon expanded into the coils to absorb heat from the atmosphere. As the ship's air passes freely over the coils, its temperature drops below the dew point, so that moisture condenses on the coils from the now supersaturated air, collecting in drip pans below and draining into the bilges or into condensate water collecting tanks. When the refrigerated air moves into the compartments its relative humidity drops as it becomes warmer. The ship is thereby made more comfortable because the air has been both cooled and partially dehumidified. It has been found paradoxically by some fleet units that in practice the boat is made more comfortable by running at least one air-conditioning unit during very cold weather; opinions have been expressed that dehumidification of the air decreased the incidence of colds among the crew, even with the heat loss entailed.


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Physiological Principles

Chart of effective temperature

Figure 130.-Effective temperature chart showing normal scale of effective temperature, applicable to inhabitants of the United States under the following conditions:

A. Clothing: Customary indoor clothing.
B. Activity: Sedentary or light muscular work.
C. Heating Methods: Convection type, i.e., warm air, direct steam or hot water radiators, plenum systems.


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18.4.2. Effective temperature.

Four basic thermal factors in the environment have been found to exert an influence on human comfort. These are: (1) The air temperature, as measured by the dry bulb thermometer; (2) the relative humidity, or percent saturation of the air with water vapor at the given temperature, as measured by the differential readings of the dry and wet bulb thermometers; (3) the air movement in cubic feet per minute, determined by an air velocity meter (velometer); and (4) the mean radiant temperature, derived by formula from the Kata globe thermometer, whose fluid bulb is in the center of a hollow ball which absorbs radiant heat from surrounding surfaces, integrating it as a human body would, independent of the heat content of the atmosphere.

Attempts have been made to correlate all four of these into one measuring device, and such instruments as the thermointegrator and the eupatheoscope have been abandoned because it was found that the thermal needs of man varied so widely at different points of the temperature scale. Instead, various formulae and nomographs have been devised for integrating the four thermal factors into workable standards of comfort.

Probably the most widely accepted index of thermal comfort was prepared by the research laboratory of the American Society of Heating and Ventilating Engineers in 1937. This index is the effective temperature, which is a sensory scale arrived at empirically using the votes of human subjects while the temperature, relative humidity, and air movement were changed in stages as independent variables during carefully controlled experiments.

In finding the effective temperature (fig. 130), the chart is entered with a line connecting the wet and dry bulb readings; the point of intersection of this line with the recorded air velocity is extended obliquely to be read on the effective temperature scale. This graph has become standard practice in the air-conditioning industry, and gives satisfactory results under hot working conditions. The fact that it does not take the heat radiation factor into consideration is not of importance if the air and the walls are at the same temperature. But this is never the case in submarines. Therefore it must be stated that there is no single thermal index capable of combining all thermal factors into a single value which is

  applicable to all situations. By adapting the mean radiant temperature into the graph, it is possible to improve the validity of the effective temperature, so that it becomes the best index for heat stress on the human body. Humidity is still weighted too heavily in the graph for use in cold climates.

Study of the graph shows the results on the effective temperature of changing a thermal factor. The effective temperature is raised by increasing the thermometer reading, by increasing the relative humidity, or by decreasing the velocity of air flow. These factors, as well as estimates of the radiant heat factor, must be appreciated by the medical officer who is reporting on the thermal habitability in any specific situation. He must also record physiological findings such as pulse rate, body temperature, and subjective reactions of the crew. Only by being able to define and recognize satisfactory air conditions will he be enabled to make valid recommendations which have meaning to the design engineer.

The optimal effective temperature is 71° F.; most naval vessels are designed not to exceed 78° optimally in the tropics, and submarines at 75-78°. A normal person can rest and sleep well at 78° effective, and can do light work at temperatures up to 80° effective if he can rest well when off watch. Sweating occurs with an effective temperature of 78° and a rise in body temperature begins with an effective temperature of 85°. He cannot do prolonged heavy work if the effective temperature is over 80°, at which temperature there is appearance of heat rashes, sleeplessness, and impaired performance. Above 85° it becomes almost impossible to work efficiently, and above 90° effective temperature the individual becomes susceptible to heat stroke.

18.4.3. Extremes of temperature.

If the atmosphere is exceedingly cold, heat is retained in the body by intradermal vasoconstriction, and heat production is increased principally by the skeletal muscles which "shiver." These compensatory phenomena are involuntary. Extra layers of clothing are put on and electric heaters are used, although running the heaters is sometimes discouraged on the premise that it is a needless waste of valuable ampere hours from the battery in the endeavor to "heat up the whole ocean." The heaters are stowed or secured during


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the finishing rates to avoid overloading them with high voltage from the battery bus.

It has been found in submarines that in the presence of elevated carbon dioxide tensions there is a decreased ability for the human organism to adapt to extremes of either heat or cold. This is postulated to be a result of the depression of the hypothalamic heat regulatory centers by carbon dioxide.

When the effective temperature becomes so hot that the individual cannot lose heat to his environment, he becomes poikilothermic. The downward thermometric gradient from the body has become reversed at this time, and heat passes into the body rather than out of it. A condition of hyperthermia exists, which progresses to high fever and heat stroke; the syndrome of heat exhaustion intervenes, however, if the person is engaged in any work. Perspiration drips from the skin without evaporating thereon; radiation, conduction, and convection all tend to increase the body temperature. Under experimental conditions, the metabolism has been shown to rise, creating a vicious cycle by contributing to the hyperthermia, until the regulatory centers themselves become imbalanced.

The ordeal of a damaged fleet submarine undergoing continuous submerged evasive maneuvers for 37 hours, when almost all machinery was secured for silent running, is cited:

"With the air-conditioning shut down the temperature within the ship went to a high figure. A temperature of 125° F. was reported in the maneuvering room. The after torpedo room and the engine room were the coolest parts of the ship. The forward torpedo room was practically unbearable * * *. The decks and bulkheads became clammy with condensed moisture. Rivulets of sweat would form and follow right behind a towel rubbed over a man's body.

"Although the temperature in the after torpedo room was probably well over 100° F., men going from the maneuvering room to the after torpedo room reported that they shivered and shook with

  the chill * * *. The liquids available for drink, fruit juices, coffee, or water, soon reached room temperature. Frequently, swallowing these liquids induced immediate vomiting, yet thirst was so great the men were constantly drinking, vomiting, and then drinking again. All of the men were nauseated. Seventy-five percent were vomiting, especially the diving officer. Profuse sweating and difficulty in keeping liquids down produced severe dehydration in many cases. No one cared to eat anything.

"The bucket brigade struggled against the mounting water in the motor room bilges and against extreme fatigue, being practically out on their feet. As the hours wore on the air commenced to get bad. Both carbon dioxide absorbent and oxygen were used, but despite that the air was very foul toward the end of the dive. Prior to the attack, the cooks removed rabbits from the icebox so that they might thaw preparatory to cooking. The odor from them became extremely disagreeable. Breathing was very difficult and headache was severe * * * many of the men were in a state of physical collapse * * * stupor * * * impossible to arouse men to go on watch * * * stations manned by volunteers * * * men who had the stamina and the will to move and think * * * others past the stage of caring what happened."

Under such conditions, the discharging batteries may attain temperatures of 130° F. or higher when not ventilated, radiating copious amounts of heat into the ship. The heat from endlessly increasing electronic installations is enough to overcome the beneficial effect of the air-conditioning units. It is not surprising to note that these men in retrospect thought it "a mistake to shut down the air-conditioning * * * would all take the noise of the air-conditioning machine and ventilation blowers in preference to enduring the heat and humidity * * * the additional noise is less dangerous than the slowed down mental reaction of extreme fatigue * * *"

 
18.5. DESIGN OF COMPARTMENTS
 
Rigorous measures to improve the livability of the compartments in a submarine are justified, if there is the probability thereby of improving morale. There has been resistance to the "pampering"   of sailors by those who do not consider the impact of weeks of incarceration on the human organism, which are incident to a largely or totally submerged war patrol. Glamorous as life aboard

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submarines may appear to the outsider, there may be long days of monotony in going about routine tasks and waiting for those few moments of contact with the enemy which come almost as a respite from boredom. In the absence of good hunting, the submariner cannot help but feel that his efforts are fruitless; it is understandable that he should tend to feel the effects of his confinement more acutely. His environment has been compared unfavorably with that of a third rate factory or a second rate jail.

18.5.1. Lighting and color.

Until recent years submarines were lighted completely by incandescent bulbs; three or four centrally located bare bulbs with wide angle reflectors were spaced in standard fashion about each compartment. With the installation of more and more dials, gauges, and cathode ray scopes to visualize for hours at a time, eyestrain increased. Tests conducted in 1944-45 at Medical Research Laboratory, New London, indicated that the visual acuity of submarine personnel following sea duty of several years had fallen below that of recruits to an extent not accountable by differences in age.

Early attempts to improve lighting of compartments were along the lines of generally established principles of visual engineering. However, it was learned that standard lighting methods required drastic modification for small shipboard compartments. The customary rules for indirect lighting, calling for high reflectance overhead and low matte finish about the bulkheads, proved infeasible because of the low overheads; the glare was great from indirect fixtures which had to be placed at eye level. It was then decided that direct lighting only must be used.

The three most prominent faults of direct lighting are glare, shadows, and high brightness ratios, the latter referring to extremely uneven distribution of light intensity in the room. The incandescent bulb, with its bright spot source of light, has been replaced by the fluorescent bulb, which emits light along a bar or line, reducing both glare points and shadows. Fluorescent light is inherently diffuse; diffusion can be increased by use of "egg crates" or metal diffusers in the light bracket. This type of light can be made directional without loss of diffusion by the use of properly designed parabolic reflectors which concentrate the light on

 

Photo to poorly lit engine panel.

Figure 131.-Poor instrument panel lighting by improper illuminating source.

work areas. High banks of dials, previously difficult to read, can now be illuminated fairly uniformly by sources placed overhead and very close to the panel (figs. 131 and 132).

Fluorescent bulbs make more efficient use of

Engine panel with florecent light illuminating it.

Figure 132.-Improved instrument panel lighting by proper illuminating source.


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electric current, so that less energy is lost in production of unwanted heat within the compartment. More light sources than before can be installed, for improved uniformity of light distribution, without increasing demand on the batteries or generators. The fixtures are smaller than the old wide angle reflectors, enabling them to be "tucked in" between ventilation lines and pipes in the overhead.

Attention to the walls, overheads, and to all surfaces in the compartment is necessary in the improvement of eye comfort and ease of seeing. High gloss paints and bright surfaces are undesirable because they produce glare, which is classed as the most harmful effect of illumination. White paint on ceilings is no longer recommended. The gleaming "bright work" which has been the pride of the Navy for years is being reduced to a minimum. Plastic laminates of low reflectance are used for table tops and for rub boards in passageways, in place of CRS.

The color of walls, ceilings, and equipment has been shown by interior decorators to have a definite effect on production and morale in all types of industrial plants. Color is a psychological experience; it is the perceptual response of a person to the release of energy within the visual spectrum. Some colors appear cool, receding, restful; these are the blues, greens, and violets, used in the rest and recreational areas. The warm, advancing shades of red, orange, and yellow are probably stimulatory to work, and used in work areas, offering a "change of pace" between work and rest areas. A color is said to be "as cool as it is blue and as warm as it is red;" pale colors are "cooler" than dark colors.

Here again drastic modifications in established principles have been found necessary in small compartments. Distribution of the warm and cool colors was used as prescribed for industry, as well as deliberately in reverse order, with about equally good results. Identical color schemes to those acceptable for some crews might be generally disliked when used aboard other ships. The matter of individual taste in colors may enter, it being hard to please everyone; however, it is known that colors change with the type of illuminant used in the particular compartment, and that the spectral distribution of paints must be specified in conjunction with the spectral emission of light sources.

  Lighting can be used to advantage as a morale factor in removing pallor from faces, making the men look more healthy to each other and to themselves as they view the mirror.

It has been estimated that about one-third of the man-hours spent during the average war patrol in World War II were spent in compartments which were "rigged for red." Red lighting is necessary in order for the adaptation of scotopic vision of those who are about to stand topside or periscope watches at night. Illumination by low levels of red light permits the continuing of regular duties, but under difficult working conditions. The true submersible is expected to minimize this problem.

18.5.2. Working areas.

Much has been written in texts and manuals of human engineering about the application of hum an anatomy, physiology, and psychology to the designing of machinery. Only in recent years have the designers of equipment begun to think of the operator as the master rather than the slave or an afterthought to the machine he operates. Formerly there was apparently little consideration given to the readability of dials, arm reach, reaction time, and other performance limits of man.

Fatigue factors are to be considered while the crewman is at his job. The motions he is required to make should be natural and efficient, with a minimum of needless movements and decisions to make. Fine adjustments are made better with fingers alone than with the forearm and wrist also. There should be proper placement of tools, materials, and controls. Any alleviation of unnecessary tiring and frustration removes a detriment to proper habitability.

18.5.3. Recreation areas.

There is no space in the submarine assigned for the sole purpose of recreation, because of the dual use principle for all room. About the only place where men can play card games or write is at the tables in the crew's mess, which of course is not available during meals or preparation for meals (figs. 133 and 134). Games, reading, hobbies, and other pursuits must be confined to semisedentary activities because of space limits. Space for movies is made usually in the forward torpedo room, the screen being placed across the tube nest.


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Crew six per table.

Figure 133.-The submarine crew's mess compartment during meal hours.

18.5.4. Sleeping spaces.

A man's bunk in a submarine, a steel frame with springs and mattress with plastic mattress cover and zippered ditty bag, is about the only home he can lay claim to, the only "castle for a home" which he possesses. Usually there is no privacy at all here. If there are not enough bunks to go around, a man awakened to go on watch is replaced in the same bunk by another coming off watch; this is called "hot bunking."

Sometimes the interval between the top of his mattress and the bunk above is as little as 15

 

Crew writing and playing games.

Figure 134.-The submarine crew's mess compartment during recreation periods.

inches, depending on the amount of sag in the springs and the weight of the occupant. If he is large he may have to get out of his bunk in order to turn over. Some top bunks cannot be occupied because of inadequate clearance of pipes above them. There are often not as many personal lockers as there are bunks, and some of these are inaccessible; most lack the capacity to stow adequate personal gear.

A recent welcome innovation is a small individual fluorescent reading lamp, mounted on an adjustable arm at the head of each bunk.

 
18.6 NOISE
 
Studies aboard fleet-type submarines have disclosed ambient noise levels of the order of 75-95 decibels even during submerged operations, the intensity depending on ship's speed and one's location in the ship. Increases well over 100 decibels were noted in the control room during the surfacing procedure; at a time when verbal transmission of information is often crucial, the low pressure blower noise rendered it difficult for shouted voices to be heard.

Engine noises, especially those made by the newer types of diesels, are believed to be immeasurably loud; that is, above 140 decibels. This degree of loudness exerts at least a temporary influence on human hearing, sufficient to impair listening acuity noticeably for hours afterward. The extent of individual susceptibility is

  undetermined, but it is generally accepted that the upper limit of tolerable noise for the average person is 130-140 decibels, for short exposure times. Hearing loss may become permanent with increased intensities and durations of exposure. Fortunately, the noise spectrum in the engineroom is peaked at relatively low frequency, which fortunately is least conducive to auditory deficit and annoyance. However, it is believed that the increased incidence of hearing loss among engineroom personnel following years of chronic exposure to noise may have a traumatic basis.

Noise at all levels has an influence on general work output. The presence of relatively high noise levels in all compartments goes almost unnoticed by personnel except in the enginerooms, probably because it is constant in nature, and


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sudden blast-type noises are infrequent. But even low noise amplitude has a definitely distracting influence on individuals who are attempting to concentrate on a job, and more errors seem to occur in proportion to the increase in noise. Loud noise causes irritability and tiredness sooner, with increase in metabolism and muscle tension in general; sympathetic stimulation is evidenced by the demonstration in some subjects of decreased saliva and gastric juice flow, decreased peristalsis, and slower visual accommodation. It is difficult to study noise apart from other accompanying stress factors in submarines, but, beyond doubt, noise may be considered a stimulus which lowers the human threshold to other types of stress.

The solution of the noise problem might seem simple at first glance; merely the attenuation of noises at their source, the dampening of reverberations in the compartments, and the shielding of

  people from noise effects by ear defenders or noise-proof watch stations. There are many obstacles to all these. It appears that a plateau has been reached in the muffling of combustion explosions in the engine by hoods, which must be detachable and portable if there is to be maintenance of the engine on board. Compartments were cork-lined long ago to reduce dripping of water from condensation, which accomplished the secondary beneficial effect of noise dampening. Ear defenders at best attenuate noise no more than 10-30 decibels; they offer protection against high frequency noise, but are of relatively little avail against the engineroom spectrum, which is peaked at 350-600 cycles per second. Resistance is encountered to the wearing of all types of ear defenders; those sailors who think them uncomfortable or inconvenient, or brag of their ability to withstand the noise manfully, must be educated and reminded of the need for these devices.
 
18.7. OTHER HABITABILITY FACTORS
 
Other items are mentioned here only briefly because they are problems not peculiar to submarines except as noted, or because they are covered elsewhere. They are still of vital importance to the welfare of persons living in a submarine.

18.7.1. Food and nutrition.

Overcrowding, confinement, excitement, limited exercise, and other environmental factors usually have an effect, but an unpredictable one, upon the appetites of the crew. There may be decreased caloric intake because of emotional tension. More often there is boredom, and eating may serve as an escape from monotony, a diversion or pastime. For no reason there may be fads for almost any type of food, from fudge to sauerkraut; these are believed to be manifestations of group psychology, for no physiological basis has been shown to be responsible for these cravings.

Dietary dissatisfaction of any kind among a group which is subject to stresses may have an adverse effect on morale. Though the submarine service maintains a reputation for the high quality of its regimen, thanks to the increased subsistence allowance for submarine rations and to procurement priorities allowed by the supply departments of bases, the submarine sailor is quick to find fault with the chow. He may be very finicky at times,

  indulging in a socially acceptable way in a rebellion against his incarceration.

Complements in excess make such demands on the cold storage facilities of the submarine that only enough fresh fruits, vegetables, and milk can be carried to last a few days, and frozen meat for a few weeks. A casualty to the refrigeration system is a tragedy to morale, but there is a cross connection between the air-conditioning and refrigeration machines to afford maximum protection against that eventuality.

18.7.2. Fresh water.

The amount of potable and battery water stored in the fresh water tanks upon departure from port, supplemented by the output of two electric vapor compression distilling units, is designed to render the fresh water supply of a modern submarine self-sustaining indefinitely, provided restrictions are placed on quantities used for bathing and laundry. It is safe to say that the water of condensation, which precipitates in large amounts on the evaporator coils of the air-conditioning units and drains from the drip pans to the bilges or to collecting tanks, can be used for these purposes. It is also felt that with the taking of certain precautions it is possible to use this condensate water for any purpose, including cooking and drinking.


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18.7.3. Sanitation.

The submarine presents problems in sanitation which are typical of all crowded ships. Air-borne infections, dermatitides, and contamination of food and eating utensils must be especially guarded against. Garbage disposal units of various types have been tried; the currently approved installation is a tube in the after battery compartment, with inner and outer doors, for discharge of bags of garbage to sea by air pressure.

Bathing is infrequent on long cruises because of limited shower and water facilities; this increases odors and skin disease.

The submarine is well adapted to fumigation for insects during availability periods at an operating submarine base.

18.7.4. Ship's motion.

Seasickness is caused by periodic acceleration on undetermined receptors in the inner ear. Certain factors as the type of ship and state of the sea are important, and the fact that most of the submarine crew are crowded below decks while the ship is on the surface might be contributory. The submarine's roll is believed to be gentler in comparison to surface vessels because of its round hull and its low transverse metacentric height. The ship motion is dampened below the surface; below periscope depth there is almost no sensation of motion except in the presence of violent seas. An interesting phenomenon which has been described is the loss of "sea legs" during long submergence periods, and a greater incidence of

  motion sickness upon surfacing than before the dive.

18.7.5. Safety.

Because of the hazardous nature of undersea duty, the fundamental principles of safety must be upheld in the design of submarines and in the familiarization of the crew with the safety features of the ship for better handling of emergencies. There are many "fail-safe" features in the construction of the machinery, and the operation of almost any mechanical system or apparatus can be taken over by standby units, cross-connection of other equipment, or hand operation. It is possible to isolate compartments and battery wells in the event of fire, flooding, or chlorine formation. Oxygen breathing apparatus, fire extinguishers, battery disconnect switches, magazine and pyrotechnic locker flooding valves, and internal salvage air lines are available to preserve the basic habitability of the ship, if the crew is adequately trained to use them efficiently when needed.

The crowding of many men into a small space predisposes to high incidence of accidents from lifting and moving of heavy objects such as torpedoes, from falling down hatches, catching the hands and feet in doors and hatches, striking the head on overhead objects, and from stumbling. In addition, the presence of multiple high voltage electric circuits, high pressure air lines, small arms, hot engines and ranges, and powerful hydraulic equipment makes it necessary that a rigid and continuous safety campaign be maintained aboard.

 
18.8. SUBMARINE CLOTHING
 
In general, the clothing requirements of submarines patrolling in warm climates are not complex. Officers above and below deck wear cotton khaki trousers and shirt and sometimes in hot weather wear shorts and short sleeved shirts. Enlisted men wear dungarees which are sometimes abbreviated into shorts on tropical patrols. Leather sandals, for wear with or without socks, are popular. They are comfortable and cool and by keeping the feet dry tend to curb the hazard of fungus infection. The soles of these sandals become slippery sometimes on greasy decks since they are not made with a nonslip sole. Another type of everyday footwear is the field shoe. This is a strong, heavy shoe made of double-tanned   leather with treaded sole and heel, and it becomes very comfortable with wear.

Officers and men wear regulation naval caps, although many go bareheaded. The baseball cap is very popular among those standing bridge watch. The inner fabricated section of the steel helmet can be used as a sun helmet and is extremely light and comfortable. During wet weather, standard issue rain gear may be worn together with suitable overshoes.

In cold climates and during cold weather in temperate climates the clothing worn below deck must be heavier. The clothing requirements in the various compartments is different. During cold weather the maneuvering room and the enginerooms


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where the diesel engines are operating are quite comfortable due to the heat given off from the machinery in those spaces. Other compartments can become quite cool, particularly in the conning tower when the upper conning tower hatch is open while on the surface. Electric heaters are provided in the various compartments, but since they draw so much current from the batteries, their use must often be curtailed. The hull which is in contact with the cold surrounding water tends to draw heat from the submarine, particularly in those areas of the hull which are not protected by cork. Much moisture may condense on these cold surfaces and "sweating" results. Sweaters and foul weather jackets are popular and Army issue wool khaki trousers are often worn by the officers.

Topside watch standing on a submarine during very cold weather is very uncomfortable. Standard issue cold weather clothing is considered to be inadequate for use in the exposed submarine bridge. This consists primarily of thick, water-resistant trousers which come well above the waist and are secured by suspenders. A parka type jacket of the same material which extends to the midthigh is put on over this. The hood of the parka has a drawstring to fit it closely about the face. High buckle type rubber boots are worn over the shoes. Hand covering is provided by leather mittens with separate knit woolen liners. Rubber mittens are also issued but these are not satisfactory. The sleeves of the jacket are open at the end and do not fit closely about the wrist. This type of clothing is quite warm and wind-resistant, but not waterproof. On the exposed bridge of a submarine it will absorb water and chill the wearer. Such clothing is very difficult to dry aboard a, submarine. The footwear is not adequate to keep the feet warm throughout a regular watch. It must be borne in mind that there is relatively little activity of the watchstanders and thus the extremities can become chilled easily. Aboard the newer type submarines spray and green water comes over the bridge more readily than in the fleet type submarine which has more flare at the bow.

With these factors in mind it becomes obvious that the modern submarine presents a special problem in cold weather clothing. Extensive research and experimentation has been done to produce


408832 O-57-19
  cold weather clothing which will meet the peculiar requirements of the modern submarine. When properly clothed, in the most severe weather, bridge personnel should remain comfortably warm and dry to maintain a reasonably long and alert watch. Since tolerance time for exposure depends primarily upon the rapid cooling of the hands and feet, adequate protection of the hands and feet is fundamental. Design of the clothing must be practical, tailoring neat, with a minimum of bulk, to facilitate rapid and easy clearance of the bridge and easy stowing of the garments. Quality of the material must incorporate a minimum of weight and bulk and a maximum of durability, practicability and safety. The garment should have rapid drying qualities, and to be effective the outfit should be waterproof, wind resistant, roomy enough to permit wearing of cold-resistant undergarments, and yet nonrestrictive to necessary movements. It may have safety measures incorporated-for example, a life preserver in case the man is washed overboard.

Such a garment has been designed and tested and in the near future it will become available for issue to all submarines (figs. 135, 136, and 137). The garment is a zippered coverall made of waterproofed nylon fabric, in a dull olive green color. The hood and vest have been combined into a unit, made of the same material as the suit and colored yellow. The face opening of the hood is lined with sponge rubber and the vest secured with one strap around the waist. The mittens are

Cold weather gear laid out on the deck.

Figure 135.-Submarine cold weather gear-component parts laid out.


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Front view of sailor in the cold weather gear.

Figure 136.-Submarine cold weather gear as worn- Front View.

 

Sailor shown from right.

Figure 137.-Submarine cold weather gear as worn- Side View.


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of the ambidexterous, single fingered type, made of rubber and designed to be worn over standard woolen mittens, and long enough to be pulled over a rubber ring in the suit's cuff to establish a waterproof seal at this point. The short boots with improved traction treads are of the vapor barrier type constructed with a flexible steel ring at the top which provides the tension for watertight seal with the rubber bottoms of the suit leg. They are designed to be worn without shoes and with a single pair of light socks. This submarine exposure suit has received enthusiastic reception by those using it during cold weather operations. It is apparent, however, that the gloves need further improvement in order to be entirely satisfactory. The boots receive the greatest praise of all in that one can stand a long watch and maintain complete foot comfort throughout the watch.

REFERENCES

18a. ComOpDevFor: Habitability in the U. S. Navy; 12 volumes (confidential).

  18b. DUFF, IVAN F., A Medical Study of the Experiences of Submarines as Recorded in 1,471 Submarine Patrol Reports in World War II, BuMed (confidential).

18c. Nay Med P-126 (Rev 1949): Manual of Naval Hygiene and Sanitation, Vol. 1, Chapters 1, 3, and 6.

18d. National Research Council, Committee on Undersea Warfare: Human Factors in Undersea Warfare, 1949.

18e. Medical Research Laboratory, New London: Report No. 131, HARRIS, J. D. and STOVER, A. D.: Noise Levels Aboard a Fleet Submarine, 1948.

18f. MRL Report No. 181, SCHAEFER, K. E.: Studies of Carbon Dioxide Toxicity: (1) Chronic CO2 Toxicity in Submarine Medicine, 10: 156-76, 1951.

18g. MRL Report No. 197, KINSEY, JACK L.: Observations on the Habitability of Submarines in Northern Waters, 11: No. 14, 1952.

18h. MRL Report No. 209, FARNSWORTH, DEAN: Developments in Submarine and Small Vessel Lighting, 11: No. 26, 1952.

18i. YAGLOU, C. P., Thermal Standards in Industry Year Book, Part 2, Amer. J. of Public Health 40: 131, May 1950.

18j. BuShips Manual, Chap. 38: Ventilation and Heating.

18k. USN Electronics Laboratory, San Diego, Human Engineering Guide for Equipment Designers, Human Factors Division, Human Engineering Section, 1951.

18l. NavPers 16160: The Fleet Type Submarine, 1946.


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