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Our Surroundings 



from the furnace to grated openings, or registers, in the rooms to 

 be heated. The efficiency of this method depends upon convection 

 currents. The same principle is used as in the jacketed stove. 

 Cold air enters the bottom part of the jacket, is warmed, and 

 rises through the pipes into the rooms. 



The cold air, in the best heating plants, is brought from the 

 outside of the building through an inlet called a cold air box. 

 In large buildings it is often forced in by motor-driven fans. 

 In small buildings enough cold air flows through the inlet to 

 replace the warmed air which is passing up the pipes. 



International Heater Co. 



A HOT Am HEATING SYSTEM 



Trace the flow of air currents. 



The air used in a hot air heating system should be moist. 

 This is accomplished in large plants by means of an apparatus 

 called a humidifier, or moistener, over which the air passes before 

 it reaches the rooms. In homes, the furnace is usually provided 

 with a water container from which sufficient moisture evaporates, 

 if it is kept filled with water. 



