Dec. lO, 1885] 



NA TURE 



cubic feet of space, in one hour the amount of carbonic 



acid would be only '' ^ ^ ~*~ - = 'o per 1000, i.e. the 



3'S 

 limit would have just been reached, and at the end of a 

 second hour, to keep the carbonic acid to this limit, another 

 3,500 cubic feet of fresh air must have been allowed to 

 enter the room. That is to say, an adult man requires when 

 at rest 3500 cubic feet of fresh air per hour ; a woman or 

 child requires proportionally less. For any individual 

 above twelve years of age, we may take as an a\erage the 

 amount of carbonic acid expired per hour as '6 cubic foot, 

 and for such an average individual 3000 cubic feet of fresh 

 air per hour is necessary. We can now appreciate the im- 

 portance of cubic space, for if we are to supply 3000 cubic feet 

 of fresh air to every individual above twelve years in a room, 

 and the amount of space, suppose, in a dormitory where ten 

 persons sleep is only 300 cubic feet per head, then 30,000 

 cubic feetof fresh air must be supplied per hour — that is to 

 say, the air of the dormitory must be completely changed 

 ten times in this period, a proceeding which would cause 

 in any but the very warmest weather a very disagreable 

 draught. But if the cubic space per head be 1000 feet, 

 then the air of the dormitory need be changed only three 

 times per hour, and if such renewal be effected steadily and 

 gradually no draught need be felt. We may mention here 

 that a certain amount of superficial or floor space is 

 necessary for each individual, for if the height of the room 

 is much over 12 feet, excess in this direction does not com- 

 pensate for deficiency in the other dimensions, although 

 the cubic space may be the same ; thus it would not be 

 the same thing to allow a man 50 square feet of floor space 

 in a room 20 feet high, as to allow him 100 square feet of 

 floor space in a room 10 feet high, although the ainount of 

 space allotted to him in each case would bs the same. It 

 may be interesting here to mention that in common lodg- 

 ing houses under police regulations, 240 cubic feet of space 

 are allotted to each adult, in barracks about 600 cubic feet, 

 in genera! hospitals about 1000 cubic feet as a rule, and in 

 infectious fever hospitals from 1500 to 3500 cubic feet — in 

 these latter institutions the floor space allowed per bed is 

 from 1 50 to 300 square feet. From the report of the royal 

 commission on the housing of the working classes it would 

 appear that even the low allowance of the common lodging 

 houses is very often not attained in the crowded rooms of 

 tenement houses, and an enormous nuriiber of cellars are 

 still inhabited in our large towns, although they presumably 

 come up to the requirements of the Public Health Acts as 

 regards their ventilation. 



Gas, candles, and lamps use up oxygen and produce 

 carbonic acid and water. A cubic foot of coal gas pro- 

 duces, when burnt, 2 cubic feet of carbonic acid, and since 

 a common burner consumes 3 cubic feet of gas in an hour, 

 it produces 6 cubic feet of carbonic acid in the same 

 period. Therefore, as much air should be supplied to 

 dilute the products of its combustion as would be 

 necessary for three or four men. It is far better, however, 

 to use such gas-lamps as are shut off from the air of the 

 room. These receive the air necessary for combustion 

 from without, and the products of combustion are carried 

 off by a special channel to the outer air. The electric 

 light uses none of the oxygen of the air and gives off no 

 carbonic acid nor water, and is for these reasons far 

 preferable to naked flames for lighting purposes. 



Ventilation is said to be carried on by natural or by 

 artificial means. In the former are included (i) diffusion 

 of gases ; (2) action of the wind by perflation and aspira- 

 tion ; (3) movements caused by differences in weight of 

 masses of air at different temperatures. By the latter, 

 although the same principles are involved, is meant ex- 

 haustion of air by heat or by steam from apartments, or 

 propulsion of air into such spaces by mechanical means, as 

 fans. Diffusion causes a rapid mixing ol different gases 

 placed in contiguity; thus the gaseous impurities of respired 

 air mix with the fresh air in a room until homogeneity is 



established. Diffusion, however, does not affect the sus- 

 pended matters which tend to fall in a ^till atmosphere. 

 Consequently organic matters which exist principally as 

 minute solids in a state of suspension in the air, are not 

 affected or removed by diffusion. The wind when in 

 motion causes a partial vacuum in the interior of tubes, 

 such as chimneys and ventilating shafts placed at right 

 angles to its course. The air in these tubes being thus 

 partially aspirated or sucked out by the action of the wind, 

 to restore the temporary vacuum so made, air from below 

 rushes up to take its place, a continual current in a per- 

 pendicular direction being thus set up. Perflation by winds 

 is the setting in motion of masses of air by the impact of 

 other misses. This action is illustrated when the windows 

 on opposite sides of the room are fully open. The room is 

 rapidly and continually flushed with air, an enormous 

 effect being produced, for it has been estimated that the 

 air of such a room may be renewed many hundred times 

 an hour, even when the movement of air outside is only 

 2 miles an hour or \\ feet per'Second, equivalent to a very 

 gentle and almost imperceptible breeze. Such a method 

 is of unquestionable utility for rapidly changing the air of 

 an unoccupied room, and may be generally put in opera- 

 tion in summer in inhabited rooms when the temperatures 

 outside and inside the house appro.ximate. In any system 

 of ventilation that depends entirely oa the wind there is 

 always the difficulty of regulating the velocity of the 

 current according to the amount of movement of the air, 

 and during complete calms the action is nil. For ventilat- 

 ing the holds and interiors of ships at sea, the wind may 

 be most advantageously utilised. A cowl placed so as to 

 face to the wind conducts the air below, whilst another 

 reversed so as to back to the wind allows the used air to 

 escape. 



The movement due to masses of air at different tem- 

 peratures is the natural force chiefly relied on for ventilat- 

 ing the interior of houses. The air of inhabited rooms 

 in this climate, except in warm summer weather, is at a 

 higher temperature than" the outer air ; hot air is lighter 

 than cold air, and will rise for cold air to take its place — 

 in fact, heated air is displaced upwards by colder and 

 denser air. In a room as usually constructed with sash 

 windows, with a fire-place and chimney, but without any 

 special means of ventilation, when a fire is burning in the 

 grate the heated air of the room in part ascends the 

 chimney-flue, and in part rises to the ceiling. Cold air 

 from outside will then enter, if the windows be closed, 

 under the door, under the skirting boards, between the 

 sashes of the window, and through any other chinks or 

 apertures due to loose fittings. The bricks and plaster of 

 the walls are also porous to a slight extent, and if not 

 covered with paint or wall paper will admit air to a 

 limited extent. Thus a large volume of air may be enter- 

 ing a room in cold weather when the fire is burning although 

 there be no visible inlets, and the amount of air thus 

 supplied may be sufficient for the needs of two or three 

 persons if it were properly distributed. But such is not 

 the case. The cold air, which enters chiefly near the floor, 

 takes us straight a course as possible to the fire-place, 

 producing a disagreeable draught to the feet of the 

 occupants, whilst the heated and vitiated air near the 

 ceiling is left undisturbed. It has been found practically 

 that to prevent draughts, and to ensure a thorough dis- 

 tribution, fresh air should be admitted into a room above 

 the heads of the occupants, an upward direction being 

 given to it, so that it may impinge on the ceiling, mix 

 with, and be warmed by, the heated air in this situation, 

 fall gently into all parts of the room, and be gradually 

 removed by means of the chimney-flue or any other 

 outlet. The inlet openings for fresh air now most in use 

 are intended to serve this purpose. For sash windows 

 Hinckes Bird's method, now so well known, of placing 

 a solid block of wood under the lower sash of the 

 window so as to raise the top of the lower sash above the 



