713 



WARMING AND VENTILATION. 



WARMING AND VENTILATION. 



714 



double, insomuch that nearly all the air that enters it comes from 

 this shaft. There are pipes under each table, and valves above the 

 tables to admit warm or cold air according to the season of the year. 

 The new Houses of Parliament are also warmed by a modification of 

 the hot-water system. 



Another large structure, the warming of which may be adduced as an 

 example of this system, is St. George's Hall, at Liverpool. Furnaces 

 and boilers send hot water through about a mile of 4-inoh pipe. A 

 fan, worked by a 10- horse power steam-engine, draws in the external 

 air, and drives it past the hot-water pipes. The warmed air enters the 

 halls and courts by apertures in the walls and floors. The temperature 

 of the pipes rarely exceeds 90. There are 120 fire-places and flues of 

 various kinds ; but there are no chimney-pots, and no smoke is made. 

 There are open fire-places in many of the rooms, in which coal is used 

 that has been partially burned, but not actually coked, previously. 

 What little smoke there is escapes, together with the vitiated air, up 

 flues at the four corners of the hall; these flues have curved deflectors 

 outside, and louvres inside, to shield the ascending currents from eddies 

 of wind. There are vast air-chambers between the ceiling of the hall 

 and the outer roof, to carry off the respired air and the products of 

 the combustion of the gas lights. 



Ventilation. There is an important, but often neglected circum- 

 stance attending the artifical warming of buildings : namely, that the 

 amount of fresh air, requisite under any condition for animal res- 

 piration, must be more and more increased in proportion to the fuel 

 burned in the room ; or, more correctly, there must be one portion 

 of air to feed combustion, and another portion to aid respiration. Now, 

 under the common arrangements of an English apartment, the open 

 fire-place and the tall chimney draw air so rapidly in that direction, 

 that the whole body of air in the room becomes speedily changed, pro- 

 vided there be an average amount of open doors, windows, crevices, &c. 

 to yield the supply. Until modern inquirers set themselves to solve 

 these two questions, or others analogous to them " How many cubic 

 feet of air are requisite for the combustion of a pound of coal ? " and, 

 " How many cubic feet of air are respired by an average man in an 

 hour?" there were no means of determining the proper amount of 

 air necessary to be supplied in a building where close stoves are used, 

 or where the methods of warming by heated air, by steam, or by hot 

 water are adopted. 



Dr. Arnott places the matter under the following form, so far as 

 respiration alone is concerned : " In respiration or breathing a man 

 draws into his chest at one time about twenty cubic inches of air, and 

 of that air a fifth part is oxygen ; of which again there is converted into 

 carbonic acid gas nearly a half. The carbonic acid, if afterwards 

 inhaled, would be noxious to the individual. About fifteen inspira- 

 tions are made in a minute, vitiating, therefore, three hundred cubic 

 inches, or nearly one-sixth of a cubic foot, of atmospheric air, but 

 which, mixing as it escapes with several times as much, renders unfit 

 for respiration at least two cubic feet under common circumstances." 

 Tredgold makes a very different estimate of the quantity of air respired 

 in a minute, and introduces other items into his calculations. In the 

 first place he reckons the average number of respirations per minute 

 twenty, and the number of cubic inches of air inspired each time 

 forty ; so that the air directly vitiated amounts to eight hundred 

 cubic inches per minute. He next takes into consideration the vapour 

 mixed with the respired air, and the insensible perspiration always 

 going on from the skin, and assumes that three cubic feet of air per 

 minute will be requisite to remove these causes of impurity. Lastly, 

 he supposes a room to contain persons in the evening, when candles, 

 lamps, &c. are lighted, and in lieu of the air vitiated by this combus- 

 tion he assumes (on what data does not clearly appear) that one-fourth 

 of a cubic foot of fresh air per minute for every individual will be 

 necessary to purify the atmosphere of the room on this ground. 

 Taking all these results together, Tredgold comes to the conclusion, 

 that when a room containing several persons is lighted to the average 

 and customary degree, it will be necessary to supply four times as 

 many cubic feet of fresh air per minute, as there are persons in the 

 room ; that is, four feet for each person. 



This supposition, of four cubic feet of fresh air per minute for each 

 individual in a room artificially lighted, of course involves the con- 

 dition that an equal quantity of vitiated air per minute must be 

 allowed to escape ; and the inquiry naturally follows, How does this 

 escape take place ? Carbonic acid gas is heavier than atmospheric air ; 

 but there are three circumstances which render respired air rather 

 lighter than the general air of a room : namely, the existence hi it of 

 nitrogen and vapour, both of less specific gravity than air, and the 

 higher temperature of the respired air than the air of a room. From 

 all these circumstances combined, it is found that respired air ascends 

 to the upper part of the room ; and it follows that the ceiling, or some 

 neighbouring part, is the proper place for an outlet. 



In the majority of buildings erected, there is no account what- 

 ever taken of the means for insuring ventilation. The fire-places 

 are constructed, the windows fixed, and the doors hung without 

 a thought being paid to the means of effecting a constant change of 

 the air contained within the apartments. But it is probable that in 

 most English rooms, provided as they are with tolerably large open 

 fire-places, and with doors which are frequently opened, the ventilation 

 i.-i mifnciently complete. The fresh air enters the room by the open 



window, the lower part of the open door, and any crevices which may 

 exist at a small height from the floor ; while the vitiated and specifi- 

 cally lighter air escapes partly up the open fire-place and chimney, 

 partly near the upper extremity of the open doors, and partly by 

 crevices around the doors and windows generally. In crowded rooms, 

 however, where the amount of vitiated breath bears a much larger 

 ratio to the cubical contents, and where the doors are generally small 

 compared with the height of the room, the impure air cannot escape 

 by these means, and some arrangements must be made near the 

 ceiling for the removal of the air. These methods are chiefly of two 

 different kinds ; the one by the use of a revolving wheel or fan, and the 

 other by the action of a chimney or tube. 



We sometimes see one of the upper panes of glass removed from a 

 window, and its place supplied by a revolving fan, as a means of ven- 

 tilating the appartment. This fan or wheel is provided with radii 

 formed like the sails of a windmill, or the blades of a screw-propeller, 

 so that any force which sets the wheel in motion will cause a current 

 of air to pass obliquely between them. But in this case the fan is 

 made to revolve merely by the impulse of the air itself, and is not 

 under the control of the inmates of a building. A more complete 

 exemplification is presented by the arrangement of the large cotton- 

 mills of the North. A fan- wheel, fan-ventilator, or wind-fan (for by 

 all these names the contrivance is known), being placed in any con- 

 venient position, is set in motion by the steam-engine of a factory, and 

 by its rotation draws out the vitiated air from a series of rooms with 

 great rapidity. The following is one variety of wind-fan used in the 

 factories. It consists of two cast-iron end-plates, A A, having a central 

 circular opening, c c c, from the circumference of which the outline of 

 each plate enlarges spirally, the point nearest the centre being near d, 

 and that farthest off being under E (Fig. 1). These two parallel plates 

 are connected by bolts, a a a ; a mantle of sheet-iron being previously 

 inserted into grooves cast in the edges of the end-plates so as to enclose 

 a cavity with an elongated outlet at B, to which a pipe is attached for 



Fig. 1. 



Fig. 2. 



carrying off the vitiated air in any direction. Within this cavity a shaft, 

 c, revolves, in bearings, b b, placed centrally in the frame-plates, A A,' 

 and cast in the same piece. On this shaft a boss is wedged fast, 

 bearing five flat arms, c c c, to which are riveted five flat plates or 

 wires, of the shape shown between a and a (Fig. 2), having a semi- 

 circular piece cut out of them on each side, about the size of the end 

 opening. On one end of the shaft, c, beyond the box-bearing, the 

 loose-and-fast pulleys, D, are fitted for receiving the driving-band, and 

 for turning the wings in the direction shown by the arrow. Thus the 

 air is driven before them out of the end orifice, B, while it enters by 

 the side openings atcec (Fig. 1). By the centrifugal force of the 

 revolving wings, the air is condensed towards their extremities, and 

 makes its escape from the pressure through the orifice, B, while it is 

 continually drawn in at the sides by its tendency to restore the 

 equilibrium. 



At the Reform Club-house a steam-engine works a revolving fan, 

 capable of throwing 11,000 cubic feet of air per minute into a sub- 

 terranean tunnel under the basement story; and the steam of con- 

 densation, from the small steam-engine which works the fan, supplies 

 three cast-iron chests with the requisite heat for warming the whole 

 building. A plan of ventilation has been adopted at the General Post- 

 OfHce, in which the fan is used. The fan, worked by a steam-engine, 

 draws fresh air down a shaft ; the air is filtered through fine wire- 

 gauze, and then sent up into all the rooms through pipes pierced with 

 small holes. 



The second mode of effecting ventilation, namely, by the use of a 

 tube or chimney opening into the air from the upper part of an 

 apartment, depends for its action on the ascensive power possessed by 

 a lofty aerial column. As the " draught " of a furnace-chimney carries 

 up the smoke, &c., more rapidly if the chimney be very lofty, so does 

 a lofty chimney exceed a low one in carrying off vitiated air : and for 

 the same reason, even if no chimney, properly so called, be provided, 

 a lofty room, furnished with appropriate openings in its ceiling, will 

 furnish a draught to carry off impure air more rapidly than a low 

 room ; and in many of our public buildings this arrangement is deemed 

 sufficient. 



Dr. Reid, when the temporary House of Commons was being pre- 

 pared, introduced the system of an artificial draught. A circular 

 shaft was built, 120 feet high, and from 8 to 11 feet in diameter. A 



