Ventilation

“ How can we detect the floating impurities in the air? What is the influence of a fire or a light? Of a hot stove? When is the ventilation perfect? What diseases are largely owing to bad air? Should the windows and doors be tightly closed, if we have no other means of ventilation? Is not a draught of air dangerous? How can we prevent this, and yet secure fresh air? ”

“ Ventilation takes care of itself in summer, when the windows are open, but in cold weather, when in our anxiety to keep the temperature comfortable we may overlook the need of fresh air, it demands close attention. The necessity of ventilation at all times is due, of course, to the composition of the atmosphere and to the changes produced in it as we breathe.
The air about us is a mixture of gases, of which oxygen and nitrogen are the most important. ”

“ In summer, as I have said, the air moves horizontally, and then windows and doors are the great means of ventilation; but as cold weather approaches, we must keep the windows shut, excepting when in bed. In winter, therefore, we must resort to flues for the means of creating a circulation, and for conveying the air from one part to another. A flue is simply a passage—a communication—for air of different temperatures. ”

“ Now, there are other conditions in which a fire-place or an opening near the floor, will not answer for ventilation. This occurs in rooms where the air is made impure by burning lamps or gas, and where the fresh air entering the room is cooler than the temperature of the room itself. ”

“ Mechanical ventilation by impulsion forces air into a building under pressure and at a high velocity destructive of diffusion causing disagreeable and dangerous draughts in the vicinity, and in the line of the inlets and outlets, the other parts of the building being left wholly unventilated, as the incoming columns of air usually travel, or are propelled, in a direct line to the nearest outlet, and there make their escape. ”

“ With natural ventilation by diffusion and extraction the evils described cannot occur, as the air is admitted at a level, and in a manner in accordance with the laws of Nature, the hot vitiated air being drawn off at the top of the building, to where it ascends, and not permitted to return, as with downward ventilation, to spread disease and death amongst those compelled to breathe it. ”

“ Ventilation.—The only way to obtain the amount of fresh air needed, when we are shut up in-doors, is to have some means provided by which the fresh air shall be brought in and the old and impure air carried out. Changing the air by such means is called ventilation. [Pg 78] Every house, and especially every sleeping-room, should be well ventilated. School-houses, churches, and other places where many people gather, need perfect ventilation. ”

“ Ventilation has a direct bearing [30] on health, although, contrary to former belief, the actual amount of oxygen in the air is not ordinarily the most important factor; even badly ventilated rooms contain more than enough oxygen to support life. The factors of prime importance in ventilation are temperature, humidity, air movement, and the number of persons in a given space since the greater the distance from one another the less is the probability that diseases will be spread. ”

“ A high authority fixes 100 cubic feet per hour per person as quite sufficient with this method of ventilation, as the average of 20 cubic feet of air which is respired by an adult per hour is expelled from the lungs at a temperature of 80° to 100°F., and ascends, along with the heated exhalations from the body, to the upper parts of the building, and is there at once drawn off, so that no part of the vitiated air can be returned to be rebreathed, as is the case when the ventilation is effected by dilution by impulsion, particularly when on the downward principle. ”

“ Thus, while recognizing the great value and importance of ventilation in a general way, they give the most definite instructions for thoroughly and most effectually preventing it, because it is at night, especially when we are asleep and cannot move from the air, that the air ought to be moved from us.
The frequent recommendations to avoid "night air" are simply recommendations to smother ourselves to death, because the foul, poisonous exhalations from our lungs cannot be removed from our chambers without being replaced by night air ; there is no other fresh air at night but night air. ”

“ The ventilation must be thorough. Bad air will poison both the sick and the well. A fireplace is, therefore, desirable. Windows should open easily. By carefully protecting the patient with extra blankets, the room may be frequently aired. If there be no direct draught, much may be done to change the air, by simply swinging an outer door to and fro many times. ”

“ In a system of ventilation it is not only a question of providing a certain volume of air from the outside, but the great problem is to provide a sufficient volume of pure air of proper temperature and of proper humidity. Air that is laden with smoke, dust and suspended matter, or that which contains gas or foul odors, is objectionable and does not meet the requirements. Therefore, the source of the air becomes important. The ventilating system must also keep the air in proper circulation at a proper velocity. ”

“ Instead of six hundred feet of space being allowed for each pupil, as perfect ventilation demands—the lowest estimate being two hundred and fifty feet—often not over one hundred feet are afforded. Instead of two thousand cubic feet of fresh air being supplied every hour for each person, and as much foul air removed, which, all physiologists assert, is needed for perfect health, perhaps no means of ventilation at all are provided, and none is secured except what an occasionally opened door, or the benevolent cracks and chinks in the building furnish the suffering lungs. ”

“ If the weather is gusty, or the situation is exposed, some other method of ventilation may be acquired. A fire is a very satisfactory, though not a theoretically perfect, method of ventilating a room. As a matter of fact, the ventilation of the room depends entirely upon the room itself and its arrangement. On his first visit you should ask the physician how the room should be ventilated, and this will relieve you from any responsibility in the matter. Remember that the commonest of all mistakes in the treatment of illness is insufficient ventilation. ”

“ HOW SHALL WE VENTILATE?—The usual method of ventilation depends upon the fact that hot air is lighter than cold air, and so the cold air tends, by the force of gravity, to fall and compel the warm air to rise. ”

“ Perfect ventilation would not be obtained, for this would only provide for the dilution of the impure air, while in perfect ventilation the impurities are not so diluted, but completely removed as fast as formed, so that no man can inspire any air which has shortly before been in his own lungs or in those of his neighbour. ”

“ Ventilation.—Since the external atmosphere, as provided by nature, is always pure, and since the air in our dwellings and other buildings is almost always impure, it becomes imperative that there should be a free communication from the one to the other. This we aim to accomplish by ventilation. As our houses are ordinarily constructed, the theory of ventilation, "to make the internal as pure as the external air," is seldom carried out. Doors, windows, and flues, the natural means of replenishing the air, are too often closed, almost hermetically, against the precious element. ”

“ In the room heated by a German stove and consequently where there cannot be a free ventilation, every individual is breathing the identical air that has circulated through the lungs of every other individual in the same place—through the air-cells of the scrofulous, the scorbutic, the asthmatic, the consumptive, &c.—air that is not only deprived of its oxygen, but loaded with animal effluvia of a very questionable character! ”

“ Wherever a building is occupied permanently with definite conditions it is far better to trust to the ventilation of Nature—natural ventilation—than to the artificial pumping in of air. During that part of the year when the windows can be opened, at least fifteen to twenty times as much fresh air would be admitted into the ward, per patient, than could be obtained if the air was pumped in, as in the Birmingham Hospital, and that was certainly much more beneficial to the patients. I visited the Victoria Hospital at Glasgow, and went through the wards. ”

“ But the theory by no means covers the art and mystery of ventilation; for ventilation is truly an art as well as a mystery. The art lies in a consummate experience of the sizes, proportions, and forms of flues, their inlets, expansions, and exits, with many other incidental adaptations necessary, in order to insure under all circumstances the regular exhaustion of any specific volume of air required, per minute. And this art has by one man been achieved. ”

“ General Ventilation.—The ordinary rules of ventilation in drying-houses apply equally to a smoke-house. There should be a slow current of air and smoke from the lowest point to the highest point in the building. ”

“ Experience, and a more enlightened knowledge of the subject, have, however, taught us that with the more perfect forms of ventilation by extraction from the upper parts of a building, to where the warm expired air naturally ascends, considerably less than the least of these estimates is sufficient for all ordinary requirements. ”

“ While it is impossible to keep the air in any room as pure as the outside atmosphere, perfectly satisfactory ventilation can be easily arranged. Some of the impure air in a house is always escaping of its own accord and its place is taken by air from the outside. ”

“ Natural means of ventilation should not be relied upon since it is difficult to get a sufficient amount of fresh air into the rooms in winter time without creating objectionable drafts which interfere with heating. Regardless of the method employed in ventilating it is a good plan to open all of the doors and windows occasionally during the day and flush the rooms with fresh air. ”

“ Thus the only ideally perfect ventilation consists in inducing a regular up-current from a level below that of the human head up to the extraction outlets at the ceiling. Under this system the bulk of fresh air required to be admitted is immensely reduced, as is also the expense of warming it to any degree considered desirable. ”

“ With the many diverse methods of ventilation which are at present in use there can be no fixed standard for determining the volume of air necessary to secure effective ventilation ; one system ensuring with a given volume a healthy atmosphere, to secure which with another system several times that volume may be required. ”

“ Robert Boyle & Son's system of ventilation, and the Local Government Board approved of the selection. This is considered to be one of the most unique examples of ventilation in this country, or indeed in the world. For the extraction of the vitiated air there are provided twenty of the ' Air-Pump ' ventilators. Fresh air is admitted all round the wards by means of openings cut through the walls at the floor level. ”

“ The popular dread of ventilation arises in a great measure from the supposition that good ventilation implies a strong draught of cold air upon your back or feet or some other unfortunately exposed place. ”

“ Methods of Ventilation.—The application of these principles of ventilation is said to be accomplished in a natural or an artificial way, according as mechanical means to utilize the forces and properties of air are used or not. But in reality natural ventilation can hardly be said to exist, since dwellings are so constructed as to guard against exposure and changes of temperature, and are usually equipped with numerous appliances for promoting change of air. ”

“ Again, perfect ventilation means the realization, in a great measure, of the condition of air out-of-doors; and few persons, probably, have estimated the enormous flow of air requisite to effect this. The ordinary notion is, that the proper renewal of the air in a room ought to be measured by the quantity passed through the lungs of an individual in any given time. ”

“ Therefore, if the temperature of the room is too nearly the same as that of the body it will be necessary to make more provision for the ventilation since the temperature of the body would not be enough greater than that of the surrounding air to create sufficient movement to carry the vitiated air away from the body. ”

“ Well, ventilation is effected by the shaft which the grub has driven through the thickness of the stone. However tiny the air-hole, it is big enough provided it be not clogged. There is no need to fear anything of the sort, even with an excess of gum. Above the ventilator rises the defensive cone, continuing, by means of its tunnel, the communication with the outer world. ”

“ Means of Ventilation.—In order that the atmosphere of a room should be changed by means of air currents, thereby securing proper ventilation, three things are necessary; (1) an inlet or inlets for the fresh air, (2) an outlet or outlets for the vitiated air, and (3) a motive force to produce and maintain the current. In systems which are distinguished by the general name of mechanical or artificial ventilation special provision is made for driving the air, by fans, or by furnaces, or by other contrivances to be described more fully below. ”

“ Beside carbonic acid there are other impurities in house air, as dust, micro-organisms of disease, exhalations from bodies, sewer gas, and the like, which accumulate and do injury when the ventilation is defective.
If every person in a house has 1000 cubic feet of air space, natural ventilation will suffice ordinarily, but artificial ventilation is needed in schoolrooms and dormitories. ”