USA > Rhode Island > Annual report of the Board of Education : together with the Annual report of the Commissioner of Public Schools of Rhode Island, 1875 > Part 21
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All know that the condition of the air in most school houses an hour after the session has' commenced, is very bad, so bad as to induce a morbid condition of the system, impairing the mental vigor of both teachers and scholars.
The cause of the trouble is commonly stated to be the presence of carbonic acid in the air which we exhale. When first thrown off from the lungs, it is warmer than the surrounding air and therefore rises to the upper part of the room ; consequently, in the popular idea, the bad air is always at the top of the room. According to the same theory it is only necessary to make a hole somewhere in or near the ceiling to let it off, and timus the room is properly ventilated. This theory of ventilation, it should be noticed, makes no provision whatever for a supply of fresh air in those school rooms (no small proportion of the whole number), which are warmed by stoves. In cases where furnaces are used, they are commonly regarded as sources merely of heat ; seldom as the means of a supply of fresh air. Registers are placed somewhere in the floor. but their size and disposition are left to convenience or to the discretion of the furnace dealer, whose sole aim, is to furnish heat, not air. True, some air must . make its way through the hot air pipes, but as soon as the temperature
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of the room is so high as to be too warm for comfort, the register is closed, thus shutting off entirely any supply of fresh air except what may creep in through the crevices around the doors and windows. If further relief from heat or close air becomes necessary, the windows are let down a little from the top. The result of this is that the cold air rushes in and fills the bottom of the room, causing dangerous draughts for those who sit near the windows, and cold feet for everybody.
If we examine this popular notion concerning the theory and practice of ventilation, we shall find its explanation of the cause of the difficulty falls as far short of stating the whole case, as the remedy proposed fails to accomplish the desired end.
As we have seen, the carbonic acid gas exhaled from the lungs is looked upon as the principal evil. Its presence is, indeed, clearly rec- ognized and the amount given off by the lungs has been determined to be . about four per cent. of the air exhaled .*
But so far from its being the principal evil in vitiated air, it is proved by experiment that a still larger proportion of carbonic acid than is con- tained in the close air of an unventilated room, may be mixed mechan- ically with ordinary air, and breathed without inconvenience. The workmen engaged in the manufacture of soda water do not experience any ill effects from breathing large quantities of it.
We must, then, seek farther for sufficient causes for the foul condition of the air in an unoccupied room. We shall discover in it not only this deleterious acid, but in still greater proportion the watery vapor and the animal matter thrown off by both lungs and skin. The amount of watery vapor given off by the lungs and skin has been variously esti- mated as from twenty to forty ounces in the twenty-four hours, or about six to twelve grains (troy) per minute. This vapor contains animal matter which seems to putrefy almost immediately after being thrown into the air. It is the source of the vile odor in an ill-ventilated room, and, in its effects on the health, is far more dangerous than carbonic acid gas, which is now generally considered acting rather as an obstruct- or of respiration than as a positive poison. No surer or more exact test than a well-educated nose has, as yet, been discovered to measure the amount of vitiating animal matter thus thrown into the air, but of its sources we can form some inferences.
The immediate emanations of the body itself we have just mentioned. All clothing, carpets and furniture are adding constantly to the air the minute particles worn off by friction. . A beam of sunlight thrown across the best kept room marks its way on the dust in the air, and we all re- member what we have seen floating in the air of school-rooms. Still another element of evil must be counted in the clothing of children of the poorer classes, which is worn and kept in homes that have never known an airing. It is easy to detect in some school rooms, the odors resulting from the different occupations of the children's parents, mingled with the scent from the frying of the family doughnuts or the smoke of
*The difference in quantity is caused by varying circumstances. The amount thrown off is least during the night and greatest during the day. It would seem that the maxi- mum and minimum amounts depend upon the state of digestion or the degree of phy- sical exertion.
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the paternal tobacco-pipe. What science hints of the germs of disease in the air about us, might startle the most careless, but such details are unnecessary when we are discussing ventilation, not for cases where great crowds of people are assembled, or where unusual causes create foul air, as in the sick wards of a hospital, but in relation to the far simpler question how we can best ventilate and warm our school rooms.
One general consideration remains to be added to this brief statement of the elements of evil in foul air. The air we breathe is exhausted of its life-giving power after a few inhalations. Deprived of its normal proportions of oxygen, it is thus rendered unfit for its proper uses. Again, the carbonic acid, the watery vapor, the animal matter and the minute dust, are soon diffused throughout the room. The question where the air is worst may be taken up later, but it must be manifest from what has been said that the entire air of a close room soon becomes vitiated in every part. Still further-we are considering rooms in which the children daily spend five or six hours, the teachers often seven or eight. The children are at an age when respiration is most active and when nature demands an ample supply of air of the purest quality.
We are, then, forced to conclude from the nature of the evil and from the imperative necessity of its entire removal, that no remedy can be successful which does not ensure a full and complete renewal of the air in the room as often as it becomes foul or dead. Nothing less than an absolute change of the whole volume of air can accomplish the object.
How often this should be done within a given time must depend upon the size of the room and the number and age of the persons occupying it. Authorities differ as to the amount of air to be supplied to insure a proper ventilation, but it is generally admitted that it should be not less than ten cubic feet per minute for each person. It may be that children require as much as adults, as they breathe faster. The actual amount of air space in the room must also be carefully considered.
The Royal Commissioners appointed by the British government to in- quire into the sanitary condition of barracks and hospitals, reported in 1857 that the capacity of the rooms should be not less than six hundred (600) cubic feet of air space for each soldier, and the supply of air, per minute and per man, not less than twenty cubic feet. Messrs. Fairbairn, Glaisher and Wheatstone reported about the same time to the general bureau of health that the supply should be from fifteen to twenty cubic feet per minute for each individual. Gen. Morin, the director of the " Conservatoire des Arts et Metiers," gives the amount at from twenty to thirty cubic feet. These estimates, it will be observed, are for adults, and, in the case of the soldiers, for sleeping rooms occupied from eight to nine hours consecutively. For children and school-rooms, the amount of air required varies, according to Gen. Morin, from seven to eighteen cubic feet per minute, in proportion to age ; and the air-space from two to three hundred feet.
It is obvious that no means of supplying air can accomplish venti- lation which does not also provide for the removal of the old and foul air. Any person accustomed to an open fire in a room partially heated by a furnace feels at once the difference in the quality of the air on going into the room of his neighbor who depends solely upon the hot air
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register. The open chimney in the one case is constantly drawing off the bad air. In the other it escapes slowly, if at all, through crevices or by the occasional opening of the door. It not unfrequently happens that the hot air ceases to enter through the register for the want of an outlet, and the door must be opened in order to start it.
Our object then, should be to seek such means of renewal and supply as shall cause and maintain a perfect balance between the incoming and the out-going air. The old fashioned fireplace is the first suggestion of the idea. The popular practice we have before mentioned was supposed to be an advance of improvement. It makes a hole near the ceiling to let out the bad air, opens the furnace registers, and considers the work done. On this principle no proper diffusion of fresh air could be ob- tained. A steady current would soon be established between the regis- ter and the ventilator, leaving dead air eddying up and down in the lower parts of the room, which may be breathed over and over again before it is drawn into the main current and taken out of the room. Where a running stream passes by a cove of comparatively still water, a counter current is almost always seen setting up along the shore.
When the air from the register is heated in the winter the difficulty is increased, as the current is accelerated and cold air remains nearly un- disturbed, or settles down disagreeably upon the head and shoulders. A person sitting in a church near one of the large hot-air registers will not unfrequently be annoyed by very perceptible counter-currents of cold air which set downwards beside the ascending hot stream.
To avoid these difficulties and secure the proper diffusion of the air are the main questions in all discussions of the subject. The systems proposed seems to have divided themselves into two great classes by taking up the subject at its opposite ends, one looking to the out-going of the air, the other to its incoming, though both have as a common air the perfect balance of the two.
One system concerns itself only with supplying the air, leaving it to make its way out through ducts provided for the purpose. It accom- plishes this by blowers or fans which press the air into the room, plenum method, and may be further characterized as the mechanical. It is ex- pensive and requires great and constant care in working, while its suc- cess is sometimes doubtful. For these reasons it need not farther be considered for school house ventilation.
The other system is directed to the withdrawal of the foul air, and this may be accomplished by means of natural laws requiring no ma- chinery other than simple ducts. It is the vacuum method. It avails itself of the natural tendency of warm air to rise, which is the result of the law of the dilatation of gases.
" A volume of air heated from the freezing point to the boiling point of water (Barometer at 30 inches,) expands .375 or about 3-8 of its vol- ume, or .002 for each degree Fahr."-(Guy Gussac's law.)
If the temperature of the air in a school room is 20° higher than that of the exterior air its volume has been increased .002 x 20.04 or 1-25; consequently it is lighter than the exterior air and tends to rise. If a vertical duct or shaft, leading directly upward, and out of the building,
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be connected with such a room, a current of air will at once set up through it, (subject to the conditions hereafter stated,) unless it happens that the shaft or duct be cooled down to the exterior temperature by contact with the outer air. If necessary heat can be applied to the low- er end of the shaft, or the smoke pipe from the furnace be carried up through the duct, to increase its draught, the necessary supply of an equal amount of fresh air will be drawn into the room, either through the hot air pipes of the furnace or some special ducts prepared for the purpose, or, failing these, it will work its way in about the doors and windows.
It will readily be understood from what we have before said that the mere hap-hazard arrangement of the register in the floor and the hole in the ceiling will not answer. Good ventilation consists in the proper dis- tribution of the ducts for the out-going and in coming air, and in their proper relation and correspondence with each other, so as to secure the perfect removal of the bad air and the thorough diffusion of the new.
The power of a vertical duct to draw the air from a room results from the velocity of the flow of air through it. This velocity depends
First. Upon the difference between the external and internal tem- perature.
Second. Upon the height of the duct.
Third. Upon the resistance or friction ; that is to say, upon the straightness and smoothness of the duct.
Fourth. Upon the sufficiency of the supply of air to replace that which is drawn from the room.
The amount of air evacuated by such a duct in a given time depends on the same four conditions, and also upon the area of a cross-section of a duct, that is upon its size.
From the above principles it follows that when the height and dis- position of the vertical ducts have been determined by the character of the building, their size should be estimated for summer ventilation when there is the least difference of temperature ; and also that the duets for the upper parts of a building should be made larger than those for the rooms below, if they are required to evacuate the same amount of air. The same reasoning applies to the hot air pipes. They should be larger in area or cross section for the rooms below than for those above, be- cause they are shorter and consequently the velocity of the air would be less than in the longer pipes for the rooms above.
The question next arises as to the way of adapting the means to the end. Shall the vertical ducts lead out from the top or the bottom of the room? Shall the fresh air be taken in at the floor or at the ceiling? Which will work to the best advantage, an upward or a downward move- ment in the air of the room ?
It might seem at first a matter of small consequence where the air is taken out, since it is safe to say it would soon become bad in every part of a room, but the importance of the point will appear as we proceed.
At first sight it would seem easier to ventilate a room by the general upward movement of the air, because its tendency, when first exhaled from the lungs, is to rise.
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A cubic foot of air at 60° Fahr., dew point 40°, (Bar. 30 inches,) will weigh 534.27 grs. A cubic foot of expired air at 95°, dew point 85°, containing 12.78 grs. of vapor and say four per cent. of carbonic acid, will weigh only 494.12 grs., or seven and one-half per cent. less. This tendency is further increased by the heat given out from the body, which warms the air in immediate contact with it, so as to cause upward motion enough to be measured by the anemometer.
Nevertheless this upward movement, even when aided by the flow of hot air from the furnace fails to secure a proper diffusion of the fresh air. We have shown, in discussing the claims of furnaces as ventilators, how quickly a steady current will be formed between the inlet and the outlet, leaving the bad air almost or quite unmoved, and only slowly and partially drawn into the current. If the attempt be made to diffuse the air by taking it in at several different places, it is apt to cause dis- agreeable draughts of warm air upon persons near the registers. Anoth- er objection will be found in the difficulty of heating a room ventilated in this way, because the hot air is drawn off too rapidly, while the great mass of cold air remains at the bottom of the room, thus making a marked difference of temperature between the air at the floor of the room and that at the level of the head, amounting often to six or seven de- grees.
If, on the other hand, we connect the duct withdrawing the air with the lower part of the room, we shall have, in the first place, an advan- tage as obvious as it is important, in the removal of the foul air as near- ly as possible at its source. By that law of the diffusion of gases, by w. ich acriform bodies diffuse themselves through each other's masses to an unlimited extent, the carbonic acid in expired air would undoubted- ly be diffused throughout the whole room. The aqueous vapor, loaded with animal matter, must also contaminate the whole atmosphere so that, although after a full sebool room has been shut up an hour, it would be hard to say where the air in it is worst, it is plain that the evil can be reached at its source, and should be removed at once before it spreads through the whole apartment. By using the downward movement the dust also (no small part of the trouble,) will be drawn off immediately and not scattered everywhere. The emanations from skin and clothing are got rid of far sooner, and the clean and tidy children will not suffer so much from their less tidy neighbors. The good accomplished by the open fire place is precisely on this principle of taking the air out of the bottom of the room. The whole subject may be well illustrated by the case of a reservoir or pond where some special cause of defilement exist at one end. If, instead of drawing or pumping out the foul water as nearly at the spot as possible, an engineer should undertake to draw it off through the clean water, allowing it to diffuse itself all the way, what folly it would seem.
The foul air should be taken out by openings so distributed around the bottom of the room that the currents of withdrawal shall affect all parts of it, while the fresh air should be introduced at the top. If it comes in at a temperature lower than that of the room, it should be distributed as much as possible, and directed upward and along the ceiling, so as not to fall di- ectly upon the heads of those below.
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If the air be heated and drawn in by a constant current, it will diffuse itself under the whole ceiling, and, arranging itself in layers, the warm- est at the top, will gradually settle down through the room. The dif- fusion would be nearly or quite perfect, but for the inequal cooling of the air by contact with the outer walls. This inequality would be per- ceptible, however, only in extreme cases, and the heating of the room would be accomplished without draughts of any sort. For by taking the air out from the bottom of the room at a number of places, the velocity of the current of withdrawal through the registers can be easily made so small as not to be perceived ; a current of air of the same temperature as the rest of the room is not unpleasant unless quite rapid, while a current of a higher or a lower temperature is disagreeable, though ite velocity be no greater than the former.
Many large buildings are warmed with air heated by passing over two or three coils of steam pipes. In such cases too great heat could easily be avoided by the use of valves to shut off the steam from one or more of the coils of pipe, leaving the fresh air to flow unchecked. This plain avoids entirely the fault of shutting the register in a school room, thus excluding the fresh air as well as the heat.
If the common furnace is used, great care should be taken to manage the fire so as not to throw the dangerous gases from hard coal into the air chamber, whence they will inevitably be carried into every room. The valve in the smoke pipe often causes much harm in this way, when it is used to check the draught ; the draught itself should not be checked too soon or too much, least the coal be burned without giving out its proper amount of heat, and the poisonous carbonic oxide be evolved from it. Mistaken economy is often the unsuspected cause of the trou- ble from gas in houses and school rooms.
Can we plead too strongly for a thoughtful consideration of this sub- ject ? Fresh air is not a luxury, not even an essential comfort, but an absolute necessity for the children. The duty of providing it is imper- ative. The cost is to be counted a trifle in proportion to the good to be gained. We build our walls tight and strong to keep out the cold, and then complain we must pay money for fresh air, the most bountiful gift of nature. Let the school houses at least be planned and built, in the first instance, with free channels for the air to come and go, then the item of ventilation will make small show in the construction accounts. When the blessing of ventilation is fully understood, the most grumbling of tax payers will admit that money spent for it was never better invested. Then shall it no longer be said that teaching is more wearing than any other profession requiring the same actual labor, but teachers and schol- ars shall work without over-fatigue or listlessness in their fresh, sweet school-rooms.
SCHOOL HYGIENE.
(From the Fourth Annual Report of the Massachusetts State Board of Heath, 1874.)
To investigate the hygienic influences of the occupation of school go- ing, and offer suggestions as to the means of improving these influences, is the purpose of the present paper. No subject within the scope of the investigations of the Board of Healthi can be of greater importance to
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the state or of more vital and anxious interest to every family in it ; and since the public interest in the schools is so warm, and the public assur- ance of their immense value is so complete, as to cause a natural jeal- ousy of any criticism of them, lest it should prove a cover for an attack on our school system which might in some way impair its usefulness, it may not be inappropriate at the beginning of this inquiry to state that there is about it nothing of hostility, and that its aini is to make an im- partial investigation. Like every other occupation, school-going must have its liability to peculiar hygienic disadvantages. Let us seek to discover these, and also the means whereby they may be reduced to a minimum.
It must be considered. that this one-fifth of our population whose oc- cupation is under investigation, are all in the growing, formative, sus- ceptible stage of life, not only most readily, but most permanently af- fected by every influence to which they are subjected. Without doubt, the instinct of childhood is for frequent, almost constant, change of posi- tion and interest during the waking hours, and any steady occupation within a restricted space, may be fairly termed unnatural for children. But since the vast majority of children cannot have an "education," without some degree of violation of what may be termed the normal con- ditions of childhood, and since some education is a necessity, it becomes of the first importance to maintain a constant jealous watch over the health of school children, and to persevere in the attempt to harmonize school methods and influences with the healthy instincts of childhood. Confinement, vitiated air, enforced quiet, prolonged mental effort, the use of the eyes on small objects in trying arrangements, are all in some degree. conditions necessary to school, but threatening danger to the health of the scholars. To reduce this to a minimum, and there main- tain it, is a public duty.
If this could be accomplished at once, there would still remain a host of injurious influences which are acting on children when out of school, and for which the schools are in no way responsible. Disease, whether preventable or inevitable, poverty, ignorance, dirt, at one end of the social scale ; luxury, fashion, social dissipation and amusements at the other end-all these are harming the health of the children of Massachu- setts, far more than any school influences. But the consideration of these evils is not within the scope of the present papers, and they would not be mentioned here, except from the desire to avoid misapprehension. All that is attempted here, is a contribution to the subject of school hygiene.
In the ordinary construction of school rooms, too little attention is paid to the number and arrangement of windows ; to the mode of heat- ing and the means of ventilation. The average hot air furnace, with its liability to be badly managed, and its certainty to leak gas, is not fit to heat an apartment, which, in proportion to its size, contains so many occupants as a school room. The discoverer of cheap steam will be a benefactor. School houses should have plenty of chimneys and capaci- ous flues ; and the efficiency of an open grate as a means of ventilation, should not be forgotten.
More attention to the height and form of desks and seats, and more
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thorough ventilation are greatly needed. More care, especially with girls, in the matter of adjusting the clothing to atmospheric conditions is greatly needed. For instance, girls are in the habit of going into the open air from the school room with no other clothing than that worn in- doors, even in the coldest winter weather. Then some teachers are in the habit of opening the windows and letting a sharp current of air blow upon the heads of the children. One teacher said to me, "I like to build a rousing fire, and then open the windows."
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