n 6 Physiology. 



The Furnace. A furnace is practically a jacket stove 

 (almost always placed in a basement). Furnaces have this 

 good feature, that they are all the time sending fresh air 

 into a room. The main trouble is, the air is usually too 

 dry. There should be in the furnace a pan of water to 

 furnish moisture to the air. 



Foul-air Shafts and Fans. Although in private dwell- 

 ings heated by furnaces there is no special provision for 

 the escape of foul air, there is ordinarily sufficient renewal 

 of the air. But in public buildings there should be escape 

 flues for foul air. Frequently a large foul-air shaft is built 

 near the center of the building, and a small stove placed 

 in it to create a sufficient up-current. In many public 

 buildings the currents created by heat are not strong 

 enough to renew the air properly. Revolving fans are 

 used, which force the air, properly heated, into the room. 



Direct Heating. In heating by steam or hot water, if 

 the radiators are placed in the room they give direct or 

 radiant heat. This system is called direct heating. It 

 gives direct heat, and produces air currents within the 

 room. In itself it has no provision for renewing the air. 



Indirect Heating. In indirect heating, coils of steam 

 or hot-water pipes are placed in air shafts which lead up 

 to the rooms above, and also have ducts to the outside. 

 As the air is heated by the heat of the pipes it rises into 

 the rooms above, and fresh, cold air presses in through 

 the ducts, to be, in turn, heated and sent up. If there is 

 at the same time a proper escape for the foul air, this 

 makes an excellent system. 



A Combination of Direct and Indirect Heating. It is a 

 good plan to combine direct and indirect heating. Where 



