Necessity for Pure Air.—Too frequently the castles of the rich as well as the humble dwellings of the poor are so scantily supplied with air of proper quantity and quality as to become the breeding places of disease. Pure air is essential to our well being. Perfect health is impossible without it.

Indoor Lives.—A large part of our lives are spent indoors, and frequently under conditions which exclude pure air, the consequences of which are seen in impaired health and aggravation of disease. The more nearly the air of our homes comports in purity with that of the external atmosphere the more capable it is of sustaining the vital forces of the body.

Normal Air.—The essential elements of air are oxygen and nitrogen. Minor ingredients are found, as carbonic acid, watery vapor, traces of organic matter, and ozone, the latter a high form of oxygen.

Oxygen.—Oxygen is the active principle of air—the element necessary to the support of life. Nitrogen is a mere diluent, to prevent the oxygen from destroying everything with fire and rust. Carbonic acid is present only in small and variable quantities. It does not help to sustain animal life, but is an essential support of plant life. The presence of watery vapor in air constantly fluctuates according to temperature. When air can take no more water it is said to be saturated, the point of complete saturation being 100. Air best adapted for health contains about 50 to 75 per cent. of saturation.

Per Cent. of Air Constituents.—Pure mountain air analyzes thus, in parts of 100—

      Oxygen ................................... 20.96
      Nitrogen ................................. 79
      Carbonic acid. ...........................   .04
      Ozone .................................variable.
      Vapor ..................varies with temperature.
      Organic matter,
      Ammonia...........................minute traces.
      Suspended, matter .....................variable.

Uniform Composition of Air.—The composition of air varies but little in different parts of the globe. By the law of diffusion and the effect of winds, nature is ever dispersing the impurities which man, through ignorance, is constantly discharging into the atmosphere.


Enumeration of Causes.—Noxious gases and irritating substances given off by certain trades and manufactures, effluvia from sewage and other refuse matter, uncleanness, respiration, skin exhalations, products of combustion, are all causes of air impurities.

Avoidable Causes.—Most of the above causes are avoidable, and should be attended to promptly by removal of the cause. But ventilation must be depended upon to purify the air of dwellings, which is rendered impure mostly by the products of combustion. These products are chiefly carbonic acid, carbonic oxide, water and smoke. The product of fires may pass into the air through chimneys, but those generated by lights remain in the rooms.

Air Vitiated by Respiration.—The most common causes of deterioration of the air are respiration and cutaneous transpiration of men. We constantly change and pollute the air in our houses by depriving it of a portion of its oxygen in its passage through the lungs, and by adding to it an increased amount of carbonic acid derived both from the lungs and from the skin. Foul organic matter and moisture are also exhaled from the lungs and from the surface of the body. Carbonic acid is injurious when present in excess; but it is the organic matter in inhabited rooms that is most hurtful, and which renders the air close and offensive. These alterations and pollutions are the inevitable results of the constant and unalterable processes of life, and therefore cannot be avoided.

Object of Ventilation.—By shutting out the pure air of heaven and by polluting the limited supply within our dwellings, we attempt to thwart the design of nature and deny ourselves the blessings of health. It is evident the nearer the air in our dwellings approaches in composition the outer air the more it conforms to the natural standard of purity, and, therefore, the better adapted to the needs of the economy. This is the object intended to be accomplished by ventilation. Of course, it is not possible to attain to this standard absolutely, without dangerous exposure to currents of air or draughts. Nevertheless, by the use of well-known devices, the air of our dwellings may be rendered fresh and wholesome and not perceptibly different from the outer air.

Changes in Air Produced by Breathing.—According to Dr. de Chaumont, the changes produced by respiration and transpiration are the following:

1. The oxygen is greatly diminished.

2. The carbonic acid is largely increased.

3. A large amount of watery vapor is produced.

4. There is a considerable evolution of ammonia and organic matter.

5. A notable amount of suspended matter is set free, consisting of epithelium and molecular and cellular matter, in a more or less active condition. At the same time portions of the epithelium are constantly being given off from the skin, and even pus-cells from suppurating surfaces.

Quantity of Air Breathed.—A man breathes about fifteen or sixteen times a minute, discharging at each expiration from twenty to thirty cubic inches of air, so that in the course of a day about 350 cubic feet of air pass through the lungs. This air is warmed and loaded with watery vapor and gains a large amount of carbonic acid (nearly five per cent.), while the quantity of oxygen is greatly diminished (about five per cent.). The oxygen is diminished in direct ratio to the consumption of carbon and hydrogen in the system.

Carbonic Acid and Other Impurities.—The amount of organic matter in the air of a room vitiated by respiration increases in proportion with the carbonic acid. Thus the carbonic acid becomes a measure for the other impurities. If there is a great deal of carbonic acid present it may be inferred that the other impurities of a more injurious character are proportionally increased. It has been ascertained by numerous examinations that the organic matter is generally perceptible to the sense of smell when the carbonic acid reaches six-tenths of one volume in 1,000 volumes of room-air, and this has been taken as the limit of impurity. When it reaches one volume in 1,000 volumes the odor is very strong and the air is said to be "extremely close."

Effects of Breathing Impure Air.—if we inquire into the condition of the atmosphere in public houses, in theatres, churches, concert-halls, courthouses, schools, ball-rooms, drawing-rooms, bed-rooms in the elegant and carefully appointed houses of the rich, the comfortable-looking homes of those in fair circumstances, as well as the humble dwellings of the poor, the evidence is everywhere apparent that the subject of ventilation is too little heeded, in very many cases entirely ignored. It is fortunate for our well-being that only a portion of our lives is spent within doors. Ill ventilation being the general condition, and a very constant one, Dr. de Chaumont has felt justified in connecting it with the prevailing diseases which are the chief sources of mortality. He states, after a very critical inquiry into the subject, that we are entitled to connect the great death-rate from heart-disease, atrophy and debility and convulsions, and particularly that due to consumption and respiratory complaints, with one constant condition affecting the whole community, namely, breathing impure air.

Standard of Impurity.—The amount of carbonic acid in normal air averages four-tenths of a volume in 1,000 volumes of air, or four volumes in 10,000; and it has been determined by the best authorities that this amount ought not to be increased beyond six-tenths of a volume in 1,000. When present in excess of this amount the air of an inhabited room becomes perceptibly impure. The standard of maximum impurity as generally accepted is therefore six-tenths of a volume in 1,000—that is, four-tenths of a volume in the original air and an additional two-tenths, derived from respiration. As long as this ratio is not exceeded, the air-space may be said to be properly ventilated.

Amount of Fresh Air Required.—Having arrived at the standard of purity, the next thing to determine is the supply of fresh air required per head in each hour to maintain the air of a room within the limits of this standard. It has already been stated that an adult man gives off from his body six-tenths of a cubic foot of carbonic acid in an hour, and the amount of carbonic acid naturally in the air being four-tenths of a volume in 1,000, it is determined, by calculation, that the amount of fresh air required to be supplied per hour to each individual, in order to preserve the air-space in a state of freshness, should be 3,000 cubic feet. The following useful table is taken from Parkes' Hygiene. The parts of a volume are given in decimals:


Table to Show the Degree of Contamination of the Air (in Terms of Carbonic Acid by Respiration, and the amount of air necessary to dilute a given standard of .6 per 1,000 volumes of air, of which .4 is carbonic acid natually existing, and .2 is from respiration. In the table a deduction is made of the initial .4 volumes of carbonic acid per 1,000 for the sake of clearness.


Space Necessary for Ventilation.—From the above table it is seen that a healthy adult requires 3,000 cubic feet of air per hour to preserve the air of an inhabited room in a wholesome state of freshness. In order to secure the required change, without running risk of currents and draughts, a certain amount of cubic air space is necessary. If the room be small the air must be changed more frequently than when it is large, and as the rate at which the air passes through the smaller space is more rapid the risk of taking cold from draughts is greater.

Advantage of Large Space.—With a large room, or space, say one of 1,000 cubic feet, the problem of ventilation becomes much easier. The current of fresh air is more easily broken up and mixes more readily with the larger volume of air in the room, and the occupant, being further from the opening, does not perceive the movement of the air. It may be incidentally remarked that a large space offers greater facility for insensible ventilation, since, the larger wall-space and more numerous windows permit of a greater change of air, and thus, with equal means for ventilation, a large room will have a less degree of impurity than a small one. To a certain extent provision can be made for the requisite amount of air by the size of the room, from the fact that the air is longer in reaching the limit of admissible impurity in a large space than in a small one, but this can never be possible for any length of time; and it becomes absolutely necessary to renew the air from time to time however large the space may be. Dr. de Chaumont gives the following results of an experiment to determine the length of time it would take to bring the air to the limit of permissible impurity (six-tenths per 1,000 of carbonic acid, initial and respiratory) in unventilated spaces of dfferent sizes:

      One man in 10,000 cubic feet...............3 hours 20 minutes.
      One man in  5,000 cubic feet................1 hour 40 minutes.
      One man in  1,000 cubic feet...................... 20 minutes.
      One man in    600 cubic feet...................... 12 minutes.
      One man in    200 cubic feet....................... 4 minutes.
      One man in     50 cubic feet....................... 1 minute.
      One man in     3O cubic feet...................... 36 seconds.

Air from Pure Source.—In fixing the amount of air required per head per hour for the purposes of ventilation it is assumed that the supply obtained is of normal quality, that is, air containing on an average four-tenths of a volume of carbonic acid in 1,000 volumes. It is a fortunate circumstance that the external air maintains a remarkable uniformity of composition, the variations even in thickly-populated places not being very great. It is from this homogeneous atmosphere that we are to draw our supply for ventilation. The caution is to be observed to secure this air in its originally pure condition, or as pure as possible under given circumstances, and not after it has become polluted from any one of innumerable sources which so frequently exist in and about the house.

Distribution of Air.—The distribution of the air throughout the rooms is a matter of importance and can be accomplished by proper attention to the arrangement of the openings. As nearly as possible uniform diffusion ought to be secured, for by this means the chance of rebreathing respired air will be greatly diminished. There have been differences of opinion with regard to the relative positions of the inlets and outlets for air. Some have held that the outlets for foul air should be near the floor, so that the air denied by impurities could be immediately withdrawn and its place supplied by the purer air from above. Under some circumstances this practice may be advised, as, for example, in certain trades and arts in which the impurities, from their weight, gravitate toward the floor, and in cases where mechanical devices are used for withdrawing the air; but in dwellings, where the impurities of respired air are mainly to be contended with, and which tend to ascend on account of the temperature, the proper place for the discharge of foul air is near the ceiling.

Temperature of Dwellings.—The air of our dwellings must be comfortably warmed, for, as Dr. Russell remarks, people will prefer being poisoned comfortably to thriving in cold air. The temperature of comfort has been fixed at various points by different writers. Dr. de Chaumont fixes a standard temperature at from 63 degrees Fahrenheit to 65 degrees Fahrenheit. English writers agree pretty generally upon a temperature of from 60 degrees Fahrenheit to 65 degrees Fahrenheit. This, from an American standpoint, would seem to be too low, and a range of from 65 degrees Fahrenheit, to 70 degrees Fahrenheit would, in the main, be more satisfactory to our comfort. However, the question is one which must be determined by the sensations of the majority as to comfort. As a rule, those who are well clothed, well fed, and who are accustomed to plenty of exercise, require less warmth.

Natural Ventilation.—As a ventilating power the force of the wind is of the greatest service. In the country, where the houses are generally surrounded by pure air and are exposed to the free action of the wind, the operation of this force contributes very largely to the factors entering into good ventilation. In the closely built-up city the conditions for utilizing this agency are not so favorable. By opening the windows and doors and allowing the wind to play freely through a room a powerful ventilating effect is produced.

Window Ventilation.—Various arrangements have been proposed for utilizing the perflation of the wind. The windows of a room offer the simplest and most convenient means of securing this object. It has been advised, whenever possible, to have the windows on opposite sides of the room. These should be made to open at the top and bottom. If the top sash be lowered and the bottom sash raised, the warm air will pass out above and the cool air enter below.

Fireplace Ventilation.—The open fireplace forms a simple and most efficient outlet for ventilation; in fact, if proper inlets are provided no other form of outlet is required in dwelling houses. The open fire extracts the air from a room with great rapidity and causes an active circulation of air. The heat is obtained by radiation from the glowing coals and by radiation and reflection from the different parts of the grate. The air in the room is warmed by the fire first warming the walls, ceiling, floor and articles in the room, and these again warm the air.

Heating.—Heating appliances vary from the old log chimney fire to the modern steam heat. Fireplace heating is always to be commended both for its cheerfulness and healthfulness, and that whether the fuel be wood or coal. The open grate is the fireplace heater in modern dwellings in both city and country. In cities gas offers an agreeable substitute for coal and wood.

The Stove.—The next most agreeable and more effective heating apparatus, especially for the country, is the stove. These are now of infinite variety. They serve the double purpose of radiating heat and of giving a degree of ventilation.

Other Heating Apparatus.—Heating by cellar heaters and by steam-pipes is efficacious in the respect that heat can thus be diffused through the whole house. But there is no ventilation nor cheer connected with the systems, and they are, as a rule, expensive.

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Last Modified: Monday, 13-May-2013 15:31:47 EDT