NEED OF VENTILATION 



to supply fresh air with its greater load of oxygen in 

 their place. We must not think that in breathing we use 

 all of the oxygen from the room. This would be impossible. 

 Neither does the carbon dioxide given out from the lungs 

 make the air unfit to breathe. Recent experiments have 

 shown that man can live in 

 an atmosphere containing 

 only ten per cent oxygen, an 

 amount so small that a match 

 could not burn in it. But 

 you are all familiar with the 

 great feeling of discomfort 

 one has in a closed and 

 "stuffy" room. This dis- 

 comfort is due principally to 

 the increase in humidity, or 

 water content of the atmos- 

 phere, in the room. Circu- 

 lation of the air will to a 

 certain extent prevent this 

 discomfort. This circulation 

 may be brought about by 

 electric fans, blowers, etc., 

 in large rooms, or by proper ventilation by means of 

 windows in smaller rooms. On the other hand, water 

 in the atmosphere is absolutely necessary for health. 

 In most artificially heated rooms the air is far too dry 

 for health, as people who live in such rooms take cold 

 more easily when they go out of doors. Air may be kept 

 moist by keeping pans of water on the radiators and 

 registers. There is a certain amount of natural circulation 

 due to the difference in weight of hot and cold air. 



H.-WHIT. CIV. SCI. IN THE HOME 5 



This shows the direction of air currents 

 when it is warmer indoors than out. 

 Can you account for this ? 



