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With reference to the opening of windows, etc., for summer ventilation, a study of Fig. 6, p. 31, will enable the earetaker to see what is best to be done. He should know from what quarter the wind is blowing before the window openings are adjusted, and should be sure as to the effects of the wind. After a little thought and practice this will not be found difficult, nor is the mastery of the subject beyond the grasp of the average caretaker. The point to remember is that moving air always draws other air in the same direction. If the wind blows parallel to the side of a building; it will draw air out of any opening which is flush with it. A window which opens outwards and is splayed towards the wind, can be made to force air into a building. Wind blowing over a roof, draws air from the farther side, but any openings on the near side would be powerful inlets. By carefully noting and weighing these facts, the caretaker, having ascertained the direction of the wind, can make use of them to advantage for summer ventilation. The foregoing remarks apply so nearly to public halls as well as churches that no separate mention need be made of them.
Hitherto attention has been directed chiefly to churches' and places of worship; a few hints on the ventilation of schools will be given next. Each classroom is a small hall warmed and ventilated by itself, unless it happens that the outlets of all the classrooms are connected with one or more air:;shaft&, If fires are used in the classrooms, and foul air shafts carried up alongside the flue, and there is no other means of. heating, the caretaker can do little except to open1 the.windows so as to let as much fresh air in'as is consistent! with: reasonable comfort to the children, before they assemble; and to open the doors and windows wide, the very moment the children leave the building. If the building is heated by hot water or steam, and sufficient warm air is; admitted, it will be easy to get rid of the foul air if there1 is A-separate outlet for each classroom; and if the outlets pass into one or more shafts, it ought not to be difficult to get rid of the foul air once the area of the outlets was adjusted. Where fans are used to expel the foul air, it is still more easy to get rid of it provided warm air is admitted in good volume. Even then, however, the outlets want careful adjustment, and it is too much to expect the caretaker to do this, because it is a matter of nicety and difficulty even to experts.
Where the caretaker has several rooms, halls, or classrooms to superintend, and the outlets lead to one or more shafts, most careful attention should be given to prevent a rush of air into the shaft through one or more of the outlets. Let us suppose there are six classrooms having outlets leading into the same shaft. Four of the classrooms are occupied by large classes and require the outlets to work to their fullest power. The two other classrooms are empty, and the caretaker has left the windows open with that best of intention— to sweeten them. For want of proper adjustment, the outlets in all the classrooms are too large, but when the six classrooms are in use they draw off about equal volumes of air. When, however, one or more classrooms is empty, and the pressure of the outer air gets freely in because the windows are opened, four times as much air goes through the outlet as was the case when all the classrooms were occupied and all the windows were. shut. Furthermore, it is winter, and the air outside very cold, the result being that such a large volume of frigid air gets into the outlet shaft through the openings in the unoccupied classrooms that the ventilating power in the outlet shaft is reduced to an almost unworkable extent. The unused classroom with its open window may, therefore, do immense mischief to the general ventilation. Such a state of things requires the most careful consideration, and the caretaker will do well to regard it seriously. There are two alternatives. (1) The outlet in the classroom should be capable of being closed, and closed accordingly. This would be best, but the caretaker must open it before the room is used. (2) The windows should all be closed alike in winter when the children are in school, no matter how many classrooms are used. Where natural ventilation is relied upon, and the area of the air shaft is ample, the best plan is to arrange the windows, doors and outlets so that the pull shall be alike in each classroom. If some of the outlets are closed, the danger is that down draughts may occur, because the outer air falls down the shaft, and these must be avoided. It is impossible to lay too much stress upon the importance of studying this question of outlet action where a number enter one central shaft.
Where hot water or steam is used for heating, it will be advisable in cold weather to keep the fires well tended so that as much warm air as possible can be obtained; or, in case the windows are the only inlets, that the cold air may be warmed in the best way to secure the comfort of the children. It may happen that the atmosphere in the assembly hall in the centre of the school buildings is kept under much tension through the classrooms getting all the air they can from underneath, and around the doors leading to the hall. It is not easy to ventilate such a large room in the centre of a block of classrooms to the best advantage under the circumstances, and where one or more classroom1 is unused, the hall can receive much air from it, and, by using the passages as warm air channels, the doors leading thereto may be used as further inlets for fresh air. A wax match, or small taper will enable the caretaker to follow the air currents and learn their direction in order to understand and master some of these difficulties; but it is only fair to say that many caretakers work their buildings with great skill, whilst the managers ought to have further expert advice so that the
1 If the classroom is used to feed the hall, the outlet had better be closed, especially if it goes into a central shaft, otherwise some foul air may be aspirated out of it.
air supply might be better arranged. The atmosphere in some of the halls which are used for teaching at the same time that the classrooms are occupied, in consequence of the school being overcrowded, is usually very foul indeed. .
With regard to town halls, council chambers, and other large rooms and halls, these will be subjected to the aspiration and wind effects mentioned in Chapter II., and the action of winds upon Tobin shafts or other inlets and outlets should be carefully studied so as to become acquainted with the effects which will be experienced according to the direction of the wind. Where a complete apparatus for heating and ventilating has been arranged, and where a fan is used to drive air into the building, the feeding of the rooms with extra air, such as council chambers, etc., just when it is wanted, will be the duty of the caretaker. If the general direction of the air currents can be determined, and information obtained which will help him in the best distribution of the warmed air in winter, and the cooled air in summer, so much the better for those in the building, but by reason of the number of passages, and the manner in which the air currents are diverted according to the temperature of the air outside and the direction of the winds, the whole subject should be carefullystudied and worked out by an expert first, so that the ventilation can be better handled by the caretaker. Warm air currents do not travel always in the direction required, and when air is cooled in summer and autumn, special knowledge is necessary so as to distribute it aright. At a recent meeting of the British Association, a soiree was given in the City buildings. In the main hall where a concert" wis in progress the atmosphere was positively stifling, whilst in the corridors so much washed and Cooled air was circulating that it was dangerous to persons coming out of the hall to stand there. These City buildings were supposed to have one of the best and most effective fan-aided systems of ventilation, but for want of proper distribution the cooled air was lacking where it was most needed, and, on that occasion, at any rate, the system was a failure. Where a number of rooms and passages are intended to be heated and ventilated from one source, situated perhaps in the basement at the end of the building, it is not fair to expect the caretaker to know how to distribute the air aright unless proper provision has been made at first. Nor is it likely, either, that the driver of the engine working the fan should possess the requisite knowledge. Indeed, unless an expert has an opportunity of examining and testing the air currents in actual operation, and to form a sound opinion as to how they will be affected by the winds, it will puzzle him not a little to arrange and set out the distribution of the air so that the different rooms and halls shall get their proper share.
The same remarks apply to hospitals, and other buildings in which several rooms and wards occur. It is quite possible to ventilate these from one central source, and without particularising any one, there are many such buildings where a more or less elaborate system of heating and ventilating has been carried out. Where provision has been made for introducing large volumes of air more or less purified and warmed, the system has not always worked well, and in not a few instances what appeared on paper so feasible has proved most disappointing in working. There are some arrangements so good in general outline, that with a little care and alteration of the area of the inlets and outlets, the whole plan might be made to give admirable results, but it is to be feared that the caretaker would not be much benefited by referring to any of these instances in detail. In buildings of this kind, where mechanical appliances are used to ventilate, or where furnace action is employed, the caretaker has no. lot in the matter, the engine driver or stoker doing what little is done. On the other hand, the opening of certain windows and ventilators by those inside the building, not unfrequently results in upsetting the ventilation of