598 Our Surroundings 



means, essentially, supplying clean air that has exactly the right 

 temperature and moisture content for human comfort and health. 

 With modern equipment, it is possible now to do this in both win- 

 ter and summer. To maintain the proper temperature, a heating 

 unit must be used in winter, and a cooling unit in summer. To 

 maintain the proper moisture content, moisture must be added to 

 the atmosphere in winter and reduced in summer. The reason 

 for this is that in winter there is not enough moisture in the air 

 for health, and in summer there is usually too much for our 

 comfort. 



In both summer and winter the air is first "washed," or fil- 

 tered, to free it of dust, soot, smoke, and bacteria. This is done 

 by forcing it through fine sprays of water, through closely woven 

 moist cloth, or through fibrous material. Radiators are not used 

 in air conditioning. The conditioned air is gently circulated 

 throughout the room or building by means of a system of large 

 pipes similar to those used in the hot-air heating system. 



Air Conditioning in Theaters. Most large theaters today 

 are air-conditioned in both summer and winter. In winter the 

 air, after being washed or filtered, is passed over steam coils to 

 be heated. Then it is humidified, or given the right amount of 

 moisture, by being passed through finely sprayed water or through 

 steam jets. The air is now "conditioned" and ready to be circu- 

 lated. Powerful blowers force it upward through pipes and out 

 into the auditorium through numerous small openings in the ceil- 

 ing. It flows gently downward through the auditorium and passes 

 out through openings under the seats. This air, after being mixed 

 with a new supply of conditioned fresh air, and reheated if neces- 

 sary, is then recirculated. 



In summer the same system is used, except that the air, after 

 being washed, is sent through a cooler and dehumidifier, or device 

 for reducing the amount of moisture in the air. The cooler is 

 made on the same principle as that of the home electric refriger- 

 ator. 1 In passing through the cooler, some of the moisture in the 

 air is condensed and forms water, as cool air cannot hold so much 

 water vapor as warm air. This water is drawn off. The air is now 



1 See description on page 62. 



