Popular Science Monthly/Volume 70/January 1907/The Sanitation of Air




HYGIENE, as a science, traces the causes of disease to which mankind is exposed in every phase of life. Its practical value lies in the preventing of these causes, through the sanitation of our surroundings and the rational care of body and mind. The gradual improvement of public health and the incident saving of vital energies as the result of true hygienic living would easily make this field of knowledge rank among the most potent factors in the development of races. Unfortunately, its greater possibilities are not yet being realized, for want of application, which is, as yet, too much confined to the professions directly concerned with matters of health. The principles of hygiene must be brought home to the people at large, must grow into and form the habits of our daily life. They should, in fact, be applied in every craft and trade, led by the professions, as, for instance, by architects and engineers, upon whom depends largely the healthfulness of our homes, of a multitude of public utilities, and of the commonwealth as a whole. In architecture and engineering, the problems bearing on health should be approached in a spirit independent of mercenary considerations. They ought to be solved strictly on their merits, with a fair perspective towards hygienic quality in all questions of serviceability, ornamental features and structural needs. Such quality is often necessary to the full realization of the aim, and essential to true artistic value as well as to material success. We can not ignore the laws and lessons of nature in building up the city of enduring beauty.

In crowded industrial and commercial centers, the excessive vitiation of the atmosphere has grown to be an important factor bearing on public health. While a systematic supply of pure air to buildings has long been recognized as a necessity, the state of the outer air has not yet received the attention it deserves, and is too often accepted as a matter beyond control. Nevertheless, an inquiry into the sources of its pollution will readily show that much of it might be prevented. That it ought to be prevented is becoming more apparent as its bearing on prevailing diseases is definitely being established. The movement for better ventilation would also gain through a closer study of the causes of impure air. Abundant literature exists on standards of purity, on temperature and humidity, also on the amount of air to be supplied per capita, but comparatively little effort has been made to trace out and bring to light the less evident and often unsuspected factors of contamination, which indicate, or at least should help to determine, the logical method of relief.

The sanitation of the air is a field which has hardly been recognized as such, at least it is not carried on systematically, with that end in view, and the results of present efforts, on the whole, are distinctly behind the progress made in other lines. Indeed, its failure to meet the aggravated needs of our crowded and growing cities can actually be traced on their vital statistics.

The Bearing of Impure Air on Health

An exceptionally clear exposition of the process of breathing is contained in the short essay, 'Air, and its Relation to Vital Energy,' by Professor S. H. Woodbridge, of the Massachusetts Institute of Technology. The oxidation of organic matter within the human body is likened to the process of combustion in a boiler furnace. This analogy applies to every essential point and shows that the conditions making for efficiency in artificial heat production are also those which bear on vital energy. The intensity of combustion within the human body depends upon the rate of exchange between the carbonic acid contained in the venous blood and the oxygen brought into the lungs, or the rapidity at which the waste products brought in from the system are being diluted. A slight abnormal accumulation of this gas in the air cells of the lungs would check this outward leakage or expulsion of waste products and retard regeneration of the blood, but respiration automatically regulates this function. Exhausted air, with deficiency in oxygen and excess of carbonic acid, to sustain equal force, thus requires increased respiration, an unconscious effort, gradually lapsing as the gathering waste products react upon the blood and through it upon vitality. The weakened light of a candle flame in exhausted room air very aptly illustrates also its effect on human beings.

Exhausted Air.—Recent experiments by Fluegge, the eminent German investigator, seemingly contradict this theory. At least they make it appear that the paucity of oxygen and the simultaneous increase of carbonic acid and other waste products, have no appreciable ill effect on the average adult, but that the depression of spirits, headache and drowsiness felt in crowded, ill-ventilated assembly rooms are principally due to disturbance of the thermal functions of the body through heat and moisture. Since these excesses in temperature and humidity always accompany exhaustion they should certainly be regarded as contributory factors, which help to depress the vital powers according to their prominence. It has been asserted, also, that the human organism has long been used to the frequent breathing of foul air, and will adapt itself to any condition tolerable at all in the long run. This is true to an extent, as to the products of breathing as well as to temperature, but it is more than likely that any immunity from the habit of living in badly used air is gained at the expense of vitality.

Contaminated Air.—As distinguished from 'exhaustion' of air, or shortage of oxygen, with the corresponding increase of carbonic acid and other waste products, the term 'contamination' may be applied to impurities of gaseous and solid nature, aside from the normally unavoidable. Tins includes, for instance, gases and vapor from industrial sources, also smoke, soot and dust with its attendant bacteria.

The amount of carbonic acid found in air is commonly regarded as a measure of the degree of vitiation, but wherever pollution of the air is likely to occur independent of an increase of combustion or respiration that method of testing the purity naturally is deceptive. Indeed, contamination quite often predominates exhaustion, and should always be considered by itself, as a separate factor, according to the nature of the case. While the effect of exhausted air may have been overestimated, the bearing of contamination on health does not seem to be sufficiently realized. Its claims on vitality are of a different nature. Any admixture of foreign gases may react directly upon the blood. Such poisoning, however, is mostly due to local sources, readily detected and prevented. By far the greater mischief is done by the solid impurities afloat in the air. Although these are normally arrested by the moist, mucous surfaces of nose and throat, they will, under certain conditions, enter the lungs, fill the minute air chambers and lodge there indefinitely. Through life in smoky or dusty surroundings large portions of the lungs become useless in this manner, invite decay and the fatal attacks of bacteria. Dr. Louis Ascher, in publishing the results of his exhaustive investigations on the subject, has shown conclusively that smoky atmosphere encourages diseases of the respiratory organs, materially shortens the life of consumptives and bears distinctly on the mortality of afflicted districts. The charts of distribution of pulmonary tuberculosis in Chicago show indeed the cases to be most frequent near the cluster of railway stations. The appalling contingent of lung patients sent to the Eocky Mountains from our smoky cities of the middle west gives a sad testimony to these facts.

Still greater mischief is done by solid impurities, especially dust, as the carriers of disease germs. True, the best authorities now agree that the presence of microbes in the respiratory organs does not necessarily produce disease, and that the germs must first make their way into the system in order to develop, and find it in poor condition before they can do serious harm. Predisposition, in the form of inflammation combined with lowered vitality, seems therefore necessary to develop the more serious pulmonary diseases. Unfortunately these predisposing ailments are very prevalent and almost unavoidable, to judge only by the numerous traces of mucous sputum displayed on public thoroughfares, mostly witnesses of chronic catarrh. The first irritation is not always caused by exposure to cold, dryness or humidity, but often by soot and dust, or the depressing conditions of indoor and city life generally. As to the effect of these impurities on diseased tissue, we have recently come to authoritative information through the report of the committee on the influence of climate, made before the National Association for the Study and Prevention of Tuberculosis. By analysis of the various factors contributing to a successful cure, it was found that good results may be secured under most widely differing climatic conditions, the benefits of relative humidity, temperature, altitude, etc., being practically dependent upon the patient's general condition or constitution. It has been found, however, that, when other things are equal and the same attention is paid to diet and hygiene, the best results have always been noted where the atmosphere was purest. Indeed the report places 'Abundance and bacteriological and chemical purity of the air' as first among the beneficial influences, while the value of sunshine and the therapeutic effects of coolness, dryness, etc., are placed next in order of importance.

Surprising results seem to have been obtained lately by the outdoor treatment of pneumonia, in which very probably the greater purity of the air is a contributing factor. The success of the fresh-air colony at Seabreeze also confirms the theory that the cure is greatly assisted by the pure sea air, that is, by the absence of dust and bacteria, which irritate, and continually bring renewed infection to the receptive diseased parts. It is for this reason that outdoor life, almost anywhere, is beneficial to lung patients, since they avoid at least some of the multifarious, insidious forms of contamination peculiar to the air in the average dwelling.

All these facts point to the meaning of impure atmosphere in densely populated cities, where the seeds of disease are most abundant, and the field for infection is prepared for it, fertilized, so to speak, by all sorts of conditions and modes of life, more or less beyond one's control. A good crop of pneumonia and kindred diseases seems assured for the winter season, when the tax on vitality is severest, and indoor life in unsanitary quarters supplies the opportunity. This seems almost sufficient to explain the present situation in our large cities, which has brought about the organization of the Pneumonia Commission through the New York Board of Health. In this connection, Dr. Herman M. Biggs, the general medical officer of the board, has stated, that the number of victims claimed yearly by pneumonia increases steadily and alarmingly. In New York City alone during the first six months of 1905 one third the total number of deaths were charged to acute respiratory diseases and pulmonary tuberculosis. During that period the deaths from these causes numbered 14,091. In the corresponding period of the year before they aggregated 10,890.

When we compare the efforts of the sanitary corps in this particular direction with the systematic and thorough work done in checking certain epidemics, we can not fail to note the lack of a comprehensive system in fighting diphtheria, grip, pneumonia and other respiratory diseases, which now claim a majority of victims. The situation seems to be recognized, but is met only to a limited extent. Much good has been accomplished through sanitary inspection, stricter enforcement of the regulations against expectorating in public places, also by exhibits and other educational work, but there are many other possible lines of action which should be taken up as parts of an organized campaign for the sanitation of the air. Since the most promising measures must always be of the preventive order, we should, above all, study the causes which lead to unwholesome atmosphere.

The Causes of Impure Air

Quantities of smoke, vapor, dust and other offensive waste products are constantly discharged into the atmosphere of urban districts. The emanation of all this matter is so rapid that it becomes visible within a few hours whenever the purifying breezes die away, and yet the gathering gloom is not generally recognized as pollution of the air, but rather taken for a change in weather. According to the seasons, the solid particles like soot and dust will cause a haze, or encourage the formation of mist and fog, sometimes, during the winter, depriving a city for days of the life-giving sun.

The sources that contribute to this pollution of urban atmosphere naturally increase with the population, while the dispersal of impure matter by the natural air currents becomes more sluggish and uncertain with the growing areas of urban settlements. The density of population in certain metropolitan districts is easily ten times that of smaller cities. The rate of vitiation of the air through smoke and other waste matter must therefore be at least that much greater. Comparatively speaking, the conditions of health in a crowded community are like those prevailing on board ship. The living space is still smaller than that of the average city dwelling, but the elements contributing to the vitiation are about the same per capita, hence more concentrated and more in evidence. We know that extra labor and care are necessary on a vessel to maintain the air in a tolerable state, quite irrespective of ventilation. In cities, where dwellings and shops are built not only closer together, but are literally piled up on each other, the general contamination is likewise bound to become unwholesome unless special care is taken in disposing of waste matter that may find its way into the air. No doubt more is being done in this direction than in former days, but the rapid concentration of living quarters and industrial shops brings with it new conditions. It should be remembered that it is our pressing duty, and part of that civilization which has built cities for millions, to keep them not only inhabitable, but healthful, wholesome and pure. Elbert Hubbard in the course of his travels once observed that 'The path of civilization is strewed with tin cans' This certainly insinuates that we have not yet arrived, while tin cans and a multitude of other witnesses of neglect in civic duty are seen along the path.

The Smoke Nuisance.—Smokeless combustion is not only feasible for almost any kind of coal, but more economical if properly attended. The principal difficulty exists in the design of the proper furnace to suit the fuel and to meet the conditions under which it is burned. There ought to be no restriction on the use of bituminous or any other coal. On the other hand, no excuse should be accepted for black smoke from any source within city limits. If not willing or able to suppress it, the offensive industry must be made to move. But all the smaller and innumerable sources of medium, light and invisible smoke should also receive attention. They emit, in reality, by far the largest share of it in the average commercial and residential community, less noticeable because more diluted, but none the less objectionable. The reduction of this smoke is, for practical reasons, beyond control of local health authorities, but it can gradually be eliminated through individual action; that is, by the general concentration of light, heat and power service. The movement in this direction was started long ago with the introduction of central stations for light and power, but it is capable of much greater extension, particularly for heating and power. The bulk of the fuel should be burned at the mine, or at tide-water outside of city limits. Such concentration of combustion for various needs represents a material saving in the total amount of fuel consumed, and, therefore, of the smoke produced. It would incidentally avoid the handling of much coal and ashes and reduce the large amount of exhaust steam now seen pouring away from the numerous individual plants in certain neighborhoods. On still days, these vapors contribute perceptibly to the murkiness of the atmosphere. The use of steam power for transportation in urban and densely populated suburban districts has long since ceased to be a necessary evil and should have been prohibited years ago. It is gratifying to state that at last this much-needed economic and sanitary reform seems about to be realized.

Street Dust.—Dust of the streets is one of the principal elements in polluting the atmosphere. It is made up of innumerable substances utterly defying description. To what extent it permeates the air, even in buildings, is proved by a microscopic examination of deposits from furniture, which shows a large percentage of animal refuse, mostly horse offal, ground up by the street traffic. 'Dirt is useful matter in a wrong place,' was one of the lamented Colonel Waring's maxims. He had, indeed, not only succeeded in removing it, but was in a fair way to make it pay for the cost of removal. Sanitation and economy often go hand in hand.

Concerted action is necessary to suppress this nuisance. No one should complain about dust who is not doing his share in preventing it. Each citizen must be his own sanitary officer and each sanitary officer and employee must be made to attend to his duties on public property. Corporations operating public conveyances should also be strictly held up to their duties. A case which illustrates this point is the New York Subway. Dust from the streets, mixed with sputum and sweepings from within, are permitted to accumulate indefinitely on a roadbed of gravel, which can never be thoroughly cleaned. The trains continually stir up some of this accumulation and impart it to the air. This is an inexcusable offense from a hygienic point of view. We need only consider that an underground route has not, like a surface railway, the natural assistance of wind, rain and sun in maintaining salubrity, and that it requires extra care and attention to make up for such disadvantage. The drippings of oil will not altogether bind or lay the dust, and the present method of drawing in air through dirty sidewalk gratings can not improve matters in this respect. An easily cleaned surface and effective mechanical means should be provided to keep the road-bed and the entire tunnel 'clean as a hound's tooth.' The stuffy atmosphere often noticed in the subway is largely traceable to these impurities, which are more objectionable than the heat and the exhaustion of the air. The latter, after all, may be regarded as temporary drawbacks, while dust and bacteria inhaled during the shortest transit will cause infection, threatening disease to any one predisposed. Unless built and operated with a reasonable appreciation of hygienic science, subways may at times become a serious menace to public health, especially when grip and similar epidemics are prevailing.

Causes for Impure Air in Buildings.—Among the numerous factors which may contribute to vitiate the air in buildings, some can always be eliminated, while others are unavoidable and should be counteracted by ventilation, in one form or another. Acting on the principle that prevention is better than cure, we should pay attention first to the avoidable sources. Waste matter of any kind is certain to contaminate the air without necessarily being perceptible by odor or by any of the customary methods of testing. Dust and dried-up sputum from the street, brought in by the air or by clothing, unless frequently removed, will permeate carpets and draperies, from where it is continually stirred up, thus filling the air with all sorts of impurities, irritating and disease-bearing. The stuffy atmosphere one notices when entering certain assembly halls and churches is nearly always due to lack of energy or method in cleaning, quite often through inaccessibility in 'dirt corners' or other hygienic fault in the design of buildings.

The combustion of gas and kerosene in living rooms rapidly vitiates the air. Each burner will use up as much oxygen as several persons, besides generating heat, moisture and often sulphurous acid gas, specially injurious to nose and throat. Stoves or grates for heating or cooking by gas should invariably be connected to a-flue to carry off the products of combustion. Even if used for lighting only, the discharge from lamps becomes very objectionable without ample provision for its escape from the room.

Smoke and vapors are unavoidable wherever cooking is going on, but through immediate and effective removal at the starting point, their spread can be prevented. There is no excuse for any odors invading the living rooms; indeed, if the vapors are properly taken care of, the air in the kitchen itself can be kept reasonably wholesome and pure.

Dust, smoke, gases or hot air from industrial sources which are often allowed to contaminate the air in workshops and laboratories can be classed as avoidable factors, since it is nearly always possible to localize them. Grinding wheels, buffers or other machinery should be equipped for this purpose with devices for mechanical suction to pick up and remove the dust or fumes before they can spread and do harm. Poisonous gases in laboratories should also be removed as soon as generated. Waste heat which would otherwise become annoying should be neutralized by insulation. The design of such arrangements requires special training and experience, but the principles of it can easily be understood and insisted upon by laymen.

The Vitiation of the Air through Heating, Cooling and Ventilating Apparatus.—Every one is familiar with the discomforts of modern heating apparatus. The most frequent complaints are of dryness, disagreeable odors or stuffy atmosphere, sometimes combined with overheating. These conditions are so common that they have almost come to be regarded as unavoidable drawbacks, more or less peculiar to certain methods of heating.

Since the capacity of air to absorb moisture increases with its temperature, heating, by any method, will have a drying effect. In clear cold weather, when the atmosphere out of doors contains little moisture, the relative percentage indoors may drop below a point to which most persons are acclimated. Unless made up by internal sources, some artificial supply of moisture seems desirable in such cases. It is, however, not necessary and not desirable, as is often recommended, to go beyond, or even as far as, making up the deficiency caused by heating, since the human system is used to considerable changes without any real discomfort. Indeed, dry air, if pure, is probably more beneficial to normal adults than moist air. The principal reason why the demand for moisture in heated rooms has arisen is the irritating effect of floating dust which has been set in motion by the heating system, directly or indirectly. In the worst form this may be noticed with hot-air heating through floor registers, which invite all sorts of rubbish to fall into the flue, only to be dried and sent up again, often directly into one's nose. Radiators also, especially those with inaccessible surfaces, will gather dust. When cold, it will lay there and molest no more than that on furniture, but as soon as heat is turned on, the tiny drops of moisture, which always cling to these solid particles, will evaporate. Free of this weight, the dust is easily set in motion by the currents of warm air rising from the radiator, as may often be seen by the tell-tale shadows on the wall above. Heating apparatus thus contaminates the air with dust and bacteria which otherwise would lay undisturbed and out of harm's way. Moistening of the air will not prevent this to any extent. It increases, in fact, another source of contamination, still too common with modern heating systems—the dry distillation of the organic matter on hot surfaces. This phenomenon has recently been studied by the noted hygienists Professors Esmarch and Nussbaum, who have independently reached the conclusion, that organic dust begins to distil or singe when a radiator reaches a temperature of about 165° F., and that this process is rather encouraged by moisture, probably because the hygroscopic matter clings longer to the heated surfaces and is therefore decomposed before it rises up in the air. To reduce' the vitiating effect of heating apparatus, we must insist on the most accessible and simple styles of radiators, on which any dust can readily be seen and is apt to be removed, and on ample heating surfaces of moderate temperature which will tend to avoid the decomposition of organic matter.

Overheating by itself must be considered as vitiating the air; at least in so far as it makes it unfit, or less wholesome, according to some noted hygienists who have thoroughly investigated its effect. It seems, at any rate, to give the air a lifeless quality, which soon imparts itself to the victim of our wasteful modes of heating.

Apparatus for artificial moistening, which is now often installed in connection with heating and ventilating systems, aside from the liability of exceeding the desirable humidity, also gives opportunity for contamination of the air supply. Unless the devices are designed on sanitary principles and intelligently attended to, they are very liable to become foul and malodorous, if not unhealthy.

Like the heating of buildings, artificial cooling may also have unwholesome effects. Special provision must be made for drying the air to keep down the relative humidity in the rooms so cooled. In moist and warm weather it would otherwise reach the saturation point. Such a condition is not only uncomfortable, but can become very unhealthy. The science of artificial cooling is as yet very little understood by the average layman and any devices which do not give perfect control over humidity must be cautioned against.

Ventilating apparatus itself may become a source of contamination if improperly designed, operated or maintained. Air filters have been found, for instance, which were intended to arrest the dust, but actually also arrest nearly all the fresh air. Some of these filters can not be cleaned or renewed without spilling the very impurities collected into the air ducts and thence into the rooms. Mechanical ventilating devices too often defeat their usefulness by lack of control over air currents and temperature, which either puts them out of service, or the persons for whose benefit they were intended.

Vitiation through Animal Life.—The last, but not the least, among the sources of vitiation is the presence of animal life or of man. Theoretically, perhaps, this may be called the only unavoidable factor, or the one which must be met by ventilation. The exhalation of carbonic acid in place of the oxygen inhaled reduces the life-giving quality of the air, or its power of regenerating the blood. Exhaled air, moreover, is charged with vapor and organic matter. The substance, called effluvia, which emanates from the surface of the human body is also of organic nature. It is harmless enough when permitted to dry and disperse, but in the moist and warm air of over-crowded rooms it quickly putrefies and becomes obnoxious. It can be recognized by that pungent odor characteristic of a sweltering mass of people. Whatever ill effects may be due to effluvia come through the action of odor on the nerves, rather than through inhaling this comparatively innocuous matter. The excess of heat and moisture produced by an audience as previously mentioned is now regarded as more than a temporary discomfort, quite aside from the danger in subsequent exposure to cold. Exhaled air, effluvia and heat thus combine, in varying proportions, to make room air unfit for breathing. In crowded meeting places they are the principal sources of vitiation, which may practically determine the artificial supply of air, while, for instance, in dwellings, offices and shops with liberal space allowance and plenty of exposure they are often a negligible quantity compared with the sources of contamination.

Suggestions for Relief

The remedy for the unhealthy conditions described naturally lies in systematic sanitation of the air; indoors as well as out-of-doors. The methods of carrying on such work are indicated by the causes themselves, and some remedies have already been suggested. In regard to open air they are practically limited to measures of prevention.

Sanitation.—The New York Board of Health now sends schoolchildren to dispensaries and specialists for deafness and defective eyesight, in the hope of reclaiming them from the dullness consequent to these ills. This unquestionably helps to keep certain contagious diseases under control, and it may be justified on other grounds, but it should not be forgotten that certain unsanitary conditions, to which such diseases can often be traced, barely receive any attention in the sense of an organized campaign for purifying the air. Particular attention should be paid to the suppression of all markets and other nuisances affecting the salubrity of streets and squares surrounding schools and hospitals. The maintenance of public buildings on strict sanitary lines by systematic processes of cleaning, disinfection, repainting and repairing is also too much neglected. The movement for the better housing of the poor, however much has been accomplished, can only be called a beginning. Hundreds of the better sort of tenements are being built, but thousands are needed. If the health board has the right to condemn old rookeries, to order repairs, to pass on workshops in dingy basements and the like, there is much to be done yet on these lines.

The campaign against expectorating, in which Dr. Darlington, the present New York health commissioner, has taken an active part, is most commendable. It certainly reduces the constant danger of infection, but it does not lead far enough toward stopping its causes, the chronic catarrh and other ills largely induced by untidy streets and buildings, public and private.

Sanitary inspection has long been organized in many cities, for certain classes of buildings, but it must include all public conveyances, conveniences, highways and byways in order to be really effective. It should be supplemented by jurisdiction over hygiene in lighting, plumbing, heating and ventilation of new buildings, and in the maintenance of streets, sewers and other public works. This may seem to be a large ground to cover for the average staff of health officers, but it is not altogether a question of men, but one of influence or power of the board over other departments, which should be made to carry out their own work with due regard for hygienic requirements. Sanitation on these lines would be of particular value as an education to the citizens by way of example.

Hints on Ventilation.—The foregoing arguments should have made it clear that ventilation is not the only cure for vitiated air. It should be regarded rather as a supplementary measure, to be used where other means of sanitation can not or will not give sufficient relief. To ventilate buildings with the impure air from city streets, railway cars with smoke from the engines, subway cars with dust-laden air from the tunnel, is naturally inefficient and of questionable benefit. Efficiency in ventilation must come through wider streets and courts, cleaner thoroughfares, the abolition of smoke and dust nuisances, and last, but not least, through the design of buildings, engineering work, public conveyances and their equipment on sanitary lines.

Laws have been in effect in several states which prescribe a fixed amount of fresh air to be supplied per capita in schools and theaters. These laws do not cover the standard of purity, except perhaps as expressed by the carbonic acid test, which does not measure the worst forms of contamination. They do not always define temperature and other qualities essential to secure its benefit to people. Moreover, it is almost hopeless to enforce them in the proper spirit. Discretion might often be in order where natural conditions will help, but can not be conceded while the exact volume of artificial supply is prescribed. The chief benefit of such legislation lies in its educational effect on people. The urgent need to-day is to bring before the public again and again the most objectionable causes of impure air, especially those of preventable nature, and to promote sound judgment as to the logical and practical means of relief.

Ventilation can be effected by natural, artificial or mechanical means. Each of these three methods has its field for application. Natural ventilation is incidental to the design and construction of a building. Frame houses are subject to considerable leakage through the shrinking wood-work of walls, windows and doors and through their greater exposure to the air generally. Such ventilation may also be called spontaneous. It is generally sufficient in exposed wooden dwellings, at times even greater than necessary. Brick and stone buildings are also subject to more or less spontaneous ventilaton, which, however, does not always meet the need. In such cases, the general design of the building should be arranged deliberately to encourage a natural ingress and egress of air. For residences and offices not unduly crowded, this may suffice with a fair exposure, but often it should be supplemented by artificial means. This implies that the building must have certain features which induce a decided movement of air, such as shafts leading from kitchen and inside rooms, also fire-place flues and vents from special sources of odor. With such provisions an active removal of foul air may be effected by differences of temperature, increased possibly by waste heat available. The leading idea should be to give the most advantageous direction to the natural currents of air. Systematic supply of fresh air, combined in some form with the heating apparatus, is appropriate in many cases, particularly as it permits some control over the purity, temperature and humidity of the air entering the building.

Mechanical or forced ventilation finds application where the number of people, excess of heat, or other conditions creating unwholesome atmosphere, can not be overcome by any other method. Theaters and crowded assembly halls, class rooms, hospitals, certain laboratories and workshops, hotel kitchens, public smoking and toilet rooms, generally need a rapid renewal of air. The ventilation of such places should be positive, that is, it should not be dependent to any extent upon weather or temporarily favorable conditions. Of course, when subject to spontaneous ventilation, such rooms will require less of the artificial kind. Indeed, it is important always to utilize the natural means at hand, and to omit none of the preventive measures that may help to relieve the situation. Buildings should be designed with due regard to airing and to avoid, if possible, the necessity for a mechanical system. The latter should always be considered as a sort of emergency device and reduced to the utmost simplicity consistent with the need. Of course, simplicity must not be secured at the expense of quality or efficiency. The latter depends mostly upon the purity, perfect distribution and the control over the temperature of the air supply. Moderate volumes, well applied, are better and more economical than large quantities indifferently, indiscriminately, almost criminally introduced. When designed and equipped on the right principles, buildings will be less dependent upon the uncertainties of complex machinery, incompetence or indifference of operators, parsimoniousness of owners, and all those contigencies which so often have turned a well-intentioned, but too complicated, apparatus into a dead letter, a lot of junk, or even a nuisance and a menace to health, instead of a means of relief. The undesirability of mechanical devices increases rapidly with their complexity and age. Deterioration is bound to set in. The simplest means to accomplish the end is not only the most economical, but it is the best guarantee for successful operation in the long run.

Building Reform.—The extreme utilization of space which is the common tendency in much of our urban architecture has passed the sanitary danger line. There are too many investors, or speculators, who do not care whether a structure is fit for habitation. Unfortunately, architects do not always realize the meaning of the demands put upon them, and that those exaggerated proportions, growing out of the fight for light and air, will make sanitation more difficult and are unfair to the neighbor. When building on a plot of ground, any adjoining property should be given an equal chance for vertical expansion, giving leave to any one to do unto you the same, with profit. Some of the flagrant encroachments lately seen upon other men's right to nature's freedom have really been nothing short of criminal. The limitation of the sky scraper is really but a question of fair dealing with one's neighbor.

The campaign for tenement-house reform, lately rewarded by splendid results, has been a step in the right direction. Its bearing on the building laws is one of the most important benefits. The provisions calling for greater court area and other features calculated to relieve crowding and to assist natural ventilation should be made even more sweeping and extended to all classes of buildings.

To improve the housing, for rich and poor, and to make a city more healthful generally, we must aim to relieve this excessive crowding. A good beginning has been made by the fight for small parks. More of these breathing spots are needed, sorely needed. Healthy playroom for the children of those unbroken rows of flats is hard to obtain, but it must be secured, if only to break up the monotony of brick and stone and relieve it with some wholesome vegetation, cooling, purifying bits of nature. Even if limited to a single block, small parks could be utilized for schools, as is done frequently in smaller towns. This would be really the ideal way of securing their full benefit, the children profiting in the day, adults in the evening, and the neighborhood all the time. The plan of locating public buildings and schools on open squares or parks may be luxury in country towns, but it is a necessity in large cities from a sanitary point of view. This idea, once recognized and rooted, might be the wedge for a new method of securing sites, of making the school the excuse, or rather the necessity, for another small park. It should at once be adopted in outlying districts where space is less expensive. The finest sites set apart for public institutions have never been found too good and always will prove the best investment of public funds from every point of view. It can not but influence the private owner to plan and build with a broader purpose than the immediate commercial gain, which has demoralized the arts and crafts, the architecture of the day, and will be a testimony to future generations of the materialism of our age.

To bring daylight into the dwellings of the ignorant masses is to educate them and to banish dirt, filth and disease. More light incidentally brings more air and purer air. But there is need for sanitary reform also in the dwellings of the rich. It should begin with more sensible building plans, a return to simplicity in design and construction with a view to inducing salubrity as the first principle of hygiene. It is not so much the quantity of air that is to be considered, but rather the quality. Let us have not only more air, but purer air, as from the open country or the sea. Sanitation of the air is a lesson taught by nature. Civilization must apply it for humanity, for the wholesome enjoyment of life to all.