VENTILATION 



59 



In a well-planned building, gentle but steady fresh air currents 

 lower the temperature and the humidity, blow away the odors, 

 and keep the building well ventilated and comfortable. An 

 auditorium whose ventilating system is 

 planned for 500 people should never 

 admit 800 people. 



In houses which have no ventilating 

 system, the air should be kept fresh 

 by intelligent action in the opening 

 of doors and windows. Since rela- 

 tively few houses are equipped with a 

 satisfactory system, the following sug- 

 gestions relative to intelligent ventila- 

 tion are offered. 



1. Ventilate on the sheltered side 

 of the house. If the wind is blowing 

 from the north, open south windows. 



2. Avoid drafts in ventilation. Ven- 

 tilate by lowering windows from the 

 top rather than by raising them at the 

 bottom, unless a window board is used 

 to break the force of the incoming air 

 (Fig. 29). 



What becomes of the carbon dioxide. Although carbon 

 dioxide is constantly being produced as a result of burning, it 

 does not accumulate in the atmosphere. Normal outdoor air 

 contains only about T ^ of one per cent of it. What, then, 

 becomes of the large quantities of carbon dioxide that result 

 from combustion and oxidation ? Plants absorb it from the 

 atmosphere through their leaves, and by a wonderful process 

 break it up into oxygen and carbon. They reject the oxygen, 

 which passes back to the air, but they retain the carbon, 

 which becomes a part of their structure. Plants thus serve 



FIG. 29. An improved win- 

 dow board to allow ventila- 

 tion without draft. 



