FARM SANITATION 



527 



by arranging the pipes so that the temperature may be kept 

 uniform in all parts of the house. 



The warm-air furnace has an advantage in that a house 

 may be heated up quickly, and likewise the disadvantage that 

 the house will cool quickly when the fire goes down, owing to 

 the fact that there is no storage of heat. The hot-air furnace 

 is very bad about conducting dust and smoke into the rooms. 

 Often cheesecloth strainers are provided in the fresh air out- 

 lets to keep out the dust. The average life of a hot-air 

 furnace will not exceed 8 to 10 

 years, and when it becomes old the 

 plates are quite likely to be cracked 

 or warped in such a way that 

 there is a serious leakage of smoke 

 and gas into the rooms. It is to 

 be noted in this connection that 

 the furnace is so large that it must 

 be built in sections, and seams 

 cannot be avoided. As air does 

 not have the property of absorbing 

 a large amount of heat quickly, 

 the plates and castings are easily 

 overheated. 



In strong winds the circulation of the air in the flues is 

 seriously interfered with. Often there is a corner room more 

 exposed than the others that cannot be heated with the hot- 

 air system. 



Installation. In planning a house in which the warm-air 

 system is to be used, thought should be taken to give the fur- 

 nace a central location, that there shall be no long horizontal 

 air pipes through which it will be difficult to start a draft. 

 The size of the hot-air furnace is usually designated by the 

 diameter of the fire pot, which ranges from 20 to 30 inches 



Fis 



319. 



A typical warm-air 

 furnace. 



