BREATHING AND LIVING CONDITIONS UNDER WATER
A submarine conceals within its small compass the most concentrated technical disposition known in the art of mechanical construction, especially so in the spaces reserved for the steering gear of the boat and for the manipulation of its weapons.
The life on board becomes such a matter of habit that we can peacefully sleep at great depths under the sea, while the noise is distinctly heard of the propellers of the enemy's ships, hunting for us overhead; for water is an excellent sound conductor, and conveys from a long distance the approach of a steamer. We are often asked, "How can you breathe under water?" The health of our crew is the best proof that this is fully possible. We possessed as fellow passengers a dozen guinea pigs, the gift of a kindly and anxious friend, who had been told these little creatures were very sensitive to the ill effects of a vitiated atmosphere. They flourished in our midst and proved amusing companions.
It is essential before a U-boat submerges to drive out the exhausted air through powerful ventilating machines, and to suck in the purest air obtainable; but often in war time one is obliged to dive with the emanations of cooking, machine oil, and the breath of the crew still permeating the atmosphere, for it is of the utmost importance to the success of a submarine attack that the enemy should not detect our presence; therefore, it is impossible at such short notice to clear the air within the boat. These conditions, however, are bearable, although one must be constantly on the watch to supply in time fresh ventilation.
Notwithstanding certain assertions in the press of alleged discoveries to supply new sources of air, the actual amount remains unchanged from the moment of submersion, and there is no possibility, either through ventilators or any other device so far known in U-boat construction, to draw in fresh air under water; this air, however, can be purified from the carbonic acid gas exhalations by releasing the necessary proportion of oxygen. If the carbonic acid gas increases in excess proportion then it produces well-known symptoms, in a different degree, in different individuals, such as extreme fatigue and violent headaches. Under such conditions the crew would be unable to perform the strenuous maneuver demanded of it, and the carbonic acid must be withdrawn and oxygen admitted.
The ventilation system of the entire submarine is connected with certain chemicals, through which the air circulates, whose property is to absorb and retain the carbonic acid. Preparations of potassium are usually employed for this purpose. Simultaneously, cylinders of oxygen, under fairly high pressure, spray oxygen into the ventilation system, which is released in a measure proportionate to the number of the crew; there is a meter in the distributing section of the oxygen tubes, which is set to act automatically at a certain ratio per man. The ordinary atmosphere is bearable for a long time and this costly method of cleansing the air is used only as a last resort; the moment at which it must be employed is closely calculated to correspond, not only with the atmospheric conditions at the time of submersion, but also to the cubic quantity of air apportioned to each man according to his activities and according to the size of the boat.
It is unnecessary to clear the air artificially during a short submersion, but during prolonged ones it is advisable to begin doing so at an early hour to prevent the carbonic acid gas from gaining a disproportionate percentage, as it becomes then more difficult to control, and it is obvious that it is impossible to dissipate the fumes of cooking, the odors of the machine oil, and the breath of the crew.
Taken altogether one can live comfortably underseas, although there is a certain discomfort from the ever-increasing warmth produced by the working of the electrical machinery, and from the condensation created by the high temperature on the surface of the boat plunged in cold water, which is more noticeable in winter and in colder regions.
It is interesting to observe that the occupations of the crew determine the atmospheric conditions: the quantity of air required by a human body depends entirely on its activity. A man working hard absorbs in an hour eighty-five liters of air. Besides the commander, who is vigorously engaged in the turret,—as will be hereafter described,—the men, employed on the lateral and depth steering, and those handling the torpedo tubes, are doing hard physical work. The inactive men use up a far smaller quantity of air, and it is ascertained that a man asleep requires hourly only fifteen liters of air. A well-drilled crew, off duty, is therefore expected to sleep at once, undisturbed by the noise around them, and their efficiency is all the greater when the time comes to relieve their weary comrades. We had a wireless operator on board whose duties ceased after submersion, and he had so well perfected the art of sleeping that he never cost us more than fifteen liters of air, hourly, underseas.
The length of time that a U-boat can remain under water depends, as we stated above, on the atmospheric conditions at the moment of plunging, and on the amount of oxygen and chemicals taken on board. We can stay submerged for several days, and a longer period will probably never be necessary.