HEATING BUILDINGS 



103 



and more dense than the hot air around the furnace, so 



it flows' through the 



cold, fresh air duct 



to the furnace and 



forces the hot air 



through the hot air x 



ducts to the rooms. 



The air keeps flowing 



as long as there is 



a fire in the furnace, 



and so the rooms are 



kept warm. In most 



private houses the air 



coming into the room 



from the furnace 



escapes from the 



room through the 



cracks around the 



windows and doors. 



This method provides 



for ventilation. 



In the school building in which the author teaches, 



the hot air system of heat- 

 ing is used. The fresh air 

 coming from the outside 

 passes through cloth screens 

 to take out the dust. A 

 large fan about twelve feet 

 in diameter forces the air to 

 the hot furnaces and froni 

 SHOWING THE MOVEMENT OF AIR there into the rooms through 

 IN A SCHOOLROOM openings near the ceiling at 



one corner. The rooms are warmed by convection currents. 



Jr. 



HEATING WITH A FURNACE HOT AIR 

 SYSTEM 



