HEATING AND VENTILATION 



2752 



HEATING AND VENTILATION 



where direct-radiation systems of heating are 

 used it is advisable to place a pan of water 

 on a radiator in each room. The air is thus 

 supplied with moisture by means of evapora- 

 tion. There are now on the market patent 

 devices which accomplish this end. When the 

 indirect-radiation system is employed the fur- 

 naces are equipped with evaporating pans 

 which should be kept full of water. 



Hot Water and Steam. In modern buildings 

 and residences steam and hot-water heating 

 have largely superseded the hot-air system. 

 Though more expensive to install, steam and 

 hot-water plants can be operated with more 

 economy of fuel than the old type of furnace. 

 They give better satisfaction, for they provide 

 heat more uniformly; they are also cleaner, 

 and the central heating body is unaffected by 

 the direction or violence of the wind. The 

 latter is probably the most serious limitation 

 of the hot-air furnace. 



The essential parts of the hot-water and 

 steam plants are a hot-water heater or steam 

 boiler, a furnace, a system of pipes and radia- 

 tors. In the one case water is circulated 

 through the pipes when it has reached a tem- 

 perature of 140 F.; steam is circulated under 

 pressure at a temperature of 212 F. In the 

 water system heat is obtained as soon as the 

 water is warmed, while with the steam system 

 no heat is available until the water in the 

 boiler has developed sufficient pressure to cir- 

 culate through the pipes. Hot-water heat, 

 however, is not so quickly shut off as steam 



heat. The water system has the advantage of 

 operating noiselessly; steam when first turned 

 on usually makes itself heard. Tn point of 

 cost, a steam plant is less expensive to install 

 than the hot-water, but is more expensive to 

 operate. 



Both systems may provide heat by direct 

 or by indirect radiation. If the direct method 

 is used, the radiators are placed in the rooms 

 to be warmed; if the indirect method is em- 

 ployed, they are located in the air passages 

 leading to the rooms. When direct radiation 

 is employed the ventilation of the building 

 should receive very careful attention. 



Electric and Gas Heating. Since 1895 elec- 

 tric heaters have been quite generally used for 

 heating street-cars. Though expensive to oper- 

 ate, they are by far the most convenient heat- 

 ing devices for local transportation. In this 

 system heat is developed by the passage of 

 an electric current through a conductor that 

 offers great resistance (see ELECTRIC HEATING). 

 Gas may be burned in fireplaces, stoves or fur- 

 naces, but in most localities it costs too much 

 to supersede coal as a fuel. Gas heaters, which 

 may be attached to the ordinary lighting jet, 

 and gas fireplaces are often found in homes 

 where coal is regularly burned, and they are 

 very much appreciated when a sudden change 

 of weather brings discomfort, especially during 

 the season when the furnace is not in use. 

 The great objection to gas as a fuel is that it 

 consumes too much of the oxygen in the air. 

 See GAS. E.D.F. 



The Ventilating Problem 



The ventilating problem is a twofold one, 

 involving the expulsion of impure air as well 

 as the admittance of fresh air. Air becomes 

 foul in a room containing human beings, be- 

 cause the lungs and skin are continually throw- 

 ing off waste matter (see SKIN; BREATH). Un- 

 less there is a constant circulation of air in a 

 room, such a room speedily becomes an un- 

 wholesome place in which to stay. It has 

 been estimated that the supply of fresh air . 

 for each person in an ordinary living room 

 should be not less than 1,800 cubic feet per 

 hour. In a room fifteen feet long, twelve feet 

 wide and ten feet high there are exactly 1,800 

 cubic feet of space. If there are six persons 

 in that room the air becomes foul unless it is 

 changed six times an hour, or every ten 

 minutes. It is not necessarily true that cold 

 air is fresh air. 



It is not enough in providing for the ven- 

 tilation of a room to open the window from 

 the bottom. Fresh air cannot enter unless the 

 warm, impure air is allowed to escape; this 

 may be provided for by lowering the sash from 

 the top. Proper ventilation of the sleeping 

 room is of highest importance. Even in the 

 coldest weather all of the bedroom windows 

 should be raised from the bottom and lowered 

 from the top. Screens may be used if the 

 wind happens to be too strong, and extra bed- 

 clothing if the weather is unusually severe. 

 Sleeping in a properly-ventilated room is an 

 excellent way to resist colds, and it makes for 

 health, optimism and vitality. 



It is obvious that in theaters, churches and 

 other places of assemblage, where large num- 

 bers of people congregate, the allowance of 

 fresh air per person should be greater than in 



