MINNESOTA STATE BOARD OF HEALTH,
CHAS. N. HEWITT, M.D., Secretary.
RED WING, MINN., July 1, 1874.

DR. A. B. STUART, Winona.

DEAR DOCTOR: Your card of some days ago was duly received, and I have since been rather at a loss how to answer it. The inquiry covers the whole subject of ventilation and warming, and to answer fully, would require a treatise, and a bulky one too. I understand though, that you want a statement of the Principles of Ventilation, and even that would be a statement longer than you have the patience to read, had I the time to write it.

The air of inhabited buildings ought to be maintained as near the purity of the "open air" as possible, for to do it perfectly is practically impossible. Pettenkoffer, the great German authority, takes as the limit of permissible impurity in dwellings 1 part of carbonic acid in 1000 parts of air. Parkes, the English authority, takes (0.6) six-tenths of one part in 1000. The "open air" contains (4) four-tenths in 1000, or four parts in 10,000. To maintain Pettenkoffer's standard, 1000 cubic feet of fresh air must be supplied for every person per hour; for Parkes's standard, 3000 cubic feet fresh air per hour, per head; .7, .8, or .9 would require, respectively, 2000, 1300, and 1200, per hour of fresh air per head.

In schools, if we could keep the limit at 8 per cent. [.8 part?] carbonic acid per 1000 parts of air, that is, furnish 1500 cubic feet of fresh air per hour to each person, we would do just about the right thing.

Take an example. A school-room contains 39 pupils and one teacher, 40 persons; to maintain our standard, i. e. limit CO, to .8 in 1000 feet of the air, we shall require 1500 feet fresh air per head, and 40 times that for the school per hour, = 60,000 cubic feet. This amount will be required every one of the school hours summer and winter. In winter that amount should pass through the air chamber of the furnace every hour into the room, and through the ventilators out of the room in the same time. To pass this amount of air through a room without perceptible draught, the capacity of the room should be equal to at least 500 cubic feet of space to each individual; that would require a room about 40 x 40 x 14 feet, and the air of the room would be changed about three times an hour, which at a temperature of 70° F. could be done without perceptible draught. The heated air should come into the room in its coolest parts, and the ventilating flues should take the foul air from the floor level. I should prefer

usually double that of the grammar departments. This necessarily causes deficiency in class-rooms in the schools of the city of New York, where the children in the gallery classes are admitted from four to six years of age. In these class-rooms the attendance is usually from 150 to 200. Unless this overcrowding is prohibited by law, and the air space necessary for health allowed to each pupil, no mechanical contrivances that can be devised for the improvement of ventilation of school-buildings will ever prove effectual. From an official report made to the present New York City Board of Education, published in January, 1875, the following extract is taken, merely to show the unsanitary condition of the schools, not vouching for its scientific accuracy: "Too little regard has been had to the space which should be allotted to each pupil in the construction of the school-buildings, with a view to both. comfort and ventilation. In many class-rooms of the primary departments and schools, only about thirty cubic feet of air to each pupil are possible to be given, even with all the windows and doors open. In some recitation-rooms, only forty or fifty cubic feet are afforded. The sole consideration in furnishing the school-rooms seems to have been in these cases, to crowd as many seats together as possible. Serious maladies are frequently contracted by the pupils in these schools, because of the necessity of opening the windows even in the coolest weather. There should be, in all grades of pupils, a uniformity of treatment, mental, physical, and moral; but the fact exists that the pupils of grammar schools are furnished in nearly all the school-buildings from one hundred to one hundred and fifty cubic feet of air per pupil."

It would appear from this that the maximum of air-space for each pupil, according to the school authorities, is one hundred and fifty cubic feet; whereas, all sanitary authorities agree that three hundred cubic feet is the least amount compatible with health. The following abstract of the report on the unsanitary condition of the public schools of the city of New York, was made to the Board of Health by two of its inspectors, Drs. Viel and Post, February 4th, 1873. This report was presented and in print before I had an opportunity to review it. It is a fair statement of the condition of the schools as we had observed them; there may be some slight inaccuracy in the figures, which is no doubt typographical. I then had the sanitary supervision of schools but a few months, during which time I was busily engaged in the inspection of the schools and the supervision of the vaccination of the pupils, of whom up

wards of 40,000 were vaccinated without a death occurring from smallpox:

"E. H. JAMES, M.D., City Sanitary Inspector: Sir: Having completed the sanitary inspection of all the public school buildings, and forwarded such complaints upon each as we deem necessary, we submit the following report of the general sanitary defects in regard to ventilation, over-crowded class-rooms, faulty construction of water-closets and urinals, deficient water supply, defective drainage, and general filthy condition of the interior of the buildings. In the following views and recommendations, we are sustained by Dr. O'Sullivan, Physician to the Board of Education, in connection with whom our inspections have been made: In our opinion, not one of the numerous school edifices has proper and adequate means for thorough and perfect ventilation. While very many have ventilating flues constructed in the walls for the purpose of ventilation, yet not one that we inspected appeared to be of any practical benefit, owing either to obstruction of the flues or the want of a revolving turret on the top of the wall to produce a continuous current of air. It is apparent to the most casual observer that without heat or some mechanical appliance it is impossible to create or maintain a current of air through a flue constructed in the walls of a building. Where flues are already placed in the walls, we have recommended two openings, one ten inches from the ceiling, the other ten inches from the floor, with a revolving turret placed upon the top of the outer wall, to produce a cross current of air through the class-room, thus facilitating the egress of foul and impure air and the ingress of fresh air. It is the invariable and pernicious practice, whenever the class-rooms become overheated or the air becomes impure and offensive, to open the windows from the top, thus allowing a current of cold air to rush in upon the heads of the children, producing catarrhal and bronchial affections, without any perceptible benefit or apparent change in the impurity of the rooms.

"In the class-rooms, where proper flues are not placed in the walls, we have recommended the adoption of rotating ventilators, to be placed in the windows, which will establish a continuous cross current of air without creating a draught or causing any of the unpleasant consequences resulting from the present method of ventilating by the opening of the windows. It is of paramount importance that some prompt and decisive measures be adopted whereby the class-rooms may be provided with proper ventilation,

and, in very many of the lower or ground floor rooms, with sufficiency of light. Some of these ground floor class-rooms without any sub-cellar, and where the rays of the sun never enter, we have recommended should be vacated as totally unfit for occupation. One of these basement rooms, with over one hundred children, has only one window, and that opens into a space only eight feet. in width between the school building and a three-story brick building in rear.

"The over-crowding of many of the class-rooms in the primary schools can best be illustrated by giving the capacity of a few of the rooms, with the number of children occupying them :

"In almost every instance the privies and urinals are situated either within the school buildings or in the yards adjacent, in such proximity to the class-rooms that offensive odors from the same readily find access to the interior of the rooms. Again, the floors and walls of the urinals are constructed of wood, and soon become saturated with urine by reason of soakage, and constantly emit foul odors. We have in most instances, recommended that the floors and walls of the urinals be covered with metal or some other substance which is impervious to water.

"In the case of the privies we have recommended ventilating flues to extend to at least two feet above the top of the school building.

"Very few of the slop sinks in the schools are provided with proper traps, and offensive sewer gases escape into the class-rooms by reason of this defect. In a large number of schools, the only water supply is on the ground floor. Although the water pipes extend even to the top floor, this absence of water from the upper rooms is a serious inconvenience to both teachers and scholars."

The then Board of Education received the reports favorably, and were engaged in devising means to put the schools in thorough sanitary condition. Immediately after, the legislature made a new charter for the city, by which the members of the Board of Education were changed throughout. The duty of making the improvements suggested, devolved upon the new Board, which was. organized April 12th, 1873, but which took no action whatever on