352 A YEAR IN SCIENCE 



A comparison of inhaled and exhaled air is most 

 readily appreciated when tabulated. 



INHALED EXHALED CHANGE 



Approximately Approximately 



Nitrogen 78% Nitrogen 78% None 



Oxygen 21% Oxygen 16% Loss 25% 



Carbon dioxide .03% Carbon dioxide Increased over 100 



4.38% times 



Dust, variable Dust, almost none Decreased 



Water vapor, variable More Greatly increased 



Temperature, variable About 98 F. Increased usually 



Iii addition to the above changes, there are added to 

 the air while in the body small quantities of ill-smelling, 

 poisonous, organic matter. It is the latter which gives 

 the bad odor to a poorly ventilated room. 



Necessity of ventilation. We know that it is neces- 

 sary to have the air in a room changed. If this is not 

 done the room becomes " close. " We soon become very 

 restless, feel sleepy and stupid, and frequently headaches 

 result. Experiments seem to indicate that these results 

 are not brought about by a lack of oxygen or by an over 

 abundance of carbon dioxide. They seem rather to be 

 the result of the presence of the organic matter before 

 referred to. Much discomfort also results from air 

 which is too hot and too dry. 



Methods of ventilation. In order to ventilate it is 

 necessary not only to remove foul air, but also to bring 

 in fresh air. According to some authorities, a room 

 is not well ventilated unless it supplies each person 

 with about eighteen hundred cubic feet of air an hour. 



In dwelling houses the amount of space for each per- 



