VENTILATION, Medical Aspects of. The air of rooms is frequently rendered more oi less injurious by the accumulation of durst and other suspended matters, or by an undue pr.coortion of one or more of the normal con stituents of the air or by the adclition to it of poisoious gases. Dust consists in varying pro porticos of spores, seeds, cellular tissue, hair, epidernal cells and other animal substances, of flint-likt particles and of microscopic organisms, some o' which may be disease germs. The gases wlich most often make the air impure are carbon dioxide, carbon monoxide, illuminating gas,. hydrogen sulphide and sewer gas. The or ganic mtrogenous matter thrown off from the lungsohe nnanations from the skin and other impunties, ningled with carbon dioxide and watery vaportgive to the atmosphere of a room that odor whith is so disaueeable to those who enter from theouter air. They are the cause of that close, oPlressive sensation perceived so often in the uiventilated rooms of tenements. Of the normal cinstituents of the air, oxygen is the invitying p-Inciple. To diminish its nor mal amount.in a room by the combustion in stoves and lights.aid by the expired air min gled with organic matters is to vitiate the atmosphere.. .To.sulnly oxygen and to remove these impurities is ore of the objects of venti lation. An increase n the amount of carbon dioxide results from du combustion of any sub stance containing carboi, from the decay and putrefaction of any amnal or vegetable sub stance, from fermentation and from the respi ration of animals. But the amount of carbon dioxide in a room is an index of the amount of organic matter and the amount of this gas present is a guide to the respiratory impurity of the air.
The investigation of the air as to organic impurities is prolonged and tedious, but an in crease in the atnount of carbon dioxide which proportionately diminishes the normal amount of oxygen is readily ascertained. Those who do not fully appreciate the conditions exhibit a tendency in cold weather to keep windows and doors closed, to put on weather-strips and to overheat apartments. Fresh air is kept out and the indoor air is fouled. Sore throats. con sumption and various lung troubles result, hile disease germs arc afforded every oppor tunity to develop. Many of the dangers arising
from impure air may be obviated by suitable ventilation, by chemicals heat and steam. Im pure air undermines the 'health and changes the character of thc blood. Suitable ventilation is the free admixture of outdoor air with that of apartments, but so modified as to temperature and velocity of current as to prevent cold drafts, which are injurious, especially to the feeble, the very young and the aged, for they lower the temperature of the body and produce internal congestions.
Ventilation should take place by night as well as by day. In fact, night air is usually purer than day air and contains less carbon dioxide. Insufficient fresh air at night in the bedroom is often the cause of sleeplessness. The airing of one room by introducing the con fined air from another is not suitable ventila tion; neither is it proper ventilation to draw the air from a cellar, or to rely entirely upon the air-chamber of a furnace. If possible the air should be drawn from above the street-level, in order that it shall be comparatively free from dust and other suspended matters. The air of a room should not only be free from any dis agreeable odor, but also from a sense of close ness. To maintain the air sufficiently pure for respiratory purposes, 90 cubic meters of fresh air per hour should be supplied to each in dividual and each individual in health should have not less than 30 cubic meters of air-space. For the sick in hospitals even double this amount of air-space is none too much. Out door air may be brought into rooms through one or more layers of fine wire gauze, woolen, cotton or linen cloth fitted in frames into the windows or arranged as screens before the open windows; or it may enter through revolving metal wheels inserted into window-panes; or through small diagonal openings in the window sashes; or between the two sashes of a window, this being made possible by placing under the lower sash a board, occupying its whole width, and from three to six or more inches high; or, finally, over a cloth fastened to the lower parts of the window-frame, the lower sash of the window being raised.